Evaluation of the anterior cruciate ligament-injured high-level athlete: a narrative review

Introduction

Background

Injuries of the anterior cruciate ligament (ACL) remain a challenging pathology among high-level athletes. A recent systematic review has suggested that while 72% of elite soccer players return to sports after ACL injury, only 53% are able to perform at the preinjury level (1). Another systematic review reported that only 67.2% of American Football players are able to return to play and often experience significant negative effects on performance and career length (2). ACL injuries seem to be more common among female athletes compared to their male counterparts (3). There are also differences in terms of sport types. Elite athletes performing pivoting sports with jumping and cutting movements such as football, soccer, basketball or lacrosse are at notably higher risk of sustaining an ACL injury (3,4).

Over the past decades extensive research has been undertaken to improve the outcomes of ACL injuries. Several risk factors such as steeper posterior tibial slope (PTS), greater preoperative pivot-shift, concomitant intra- or extra-articular injuries of the knee, general joint laxity (GJL) and knee hyperextension have been identified as key factors in assessing a patient with ACL injury (5-9). The shape of the native ACL and its insertions are heterogenous from patient to patient (10). ACL reconstruction needs to be as anatomical as possible and treatment decisions should be made according to the athlete’s individual anatomical prerequisites and physical demands (11). Proper physical examination, imaging and quantitative measurements of knee kinematics are needed for diagnosis and to identify the patients individual risk factors. This narrative review aims to summarize the most recent developments and current state of the art when evaluating ACL injured high-level athletes.

Objective

To provide an overview of the current evidence on the assessment and evaluation of the ACL injured high-level athlete with focus on clinical examination, imaging and instrumented laxity measurement tools. We present this article in accordance with the Narrative Review reporting checklist (available at https://aoj.amegroups.com/article/view/10.21037/aoj-25-40/rc).

Methods

PubMed was manually searched for papers about evaluation of ACL injured athletes. Inclusion criteria were original articles and reviews written in English. Studies about clinical examination, imaging and instrumented laxity measurement were included. Additionally, further articles were included by reviewing the references of previously included publications. Single case reports and articles without abstracts were excluded. All papers were manually reviewed by the first author for content, relevance and credibility. An overview of the search strategy including search terms is provided in Table 1. Written informed consent was obtained from the patient for the publication of this article and accompanying images.

History and physical examination

The foundation of any diagnosis is a precise history. Patients with an ACL injury often report a popping sensation, giving way phenomena or acute joint effusion of the knee (12). A partial or complete tear of the ACL can be found in approximately 70% of all patients with hemarthrosis (13) and is often accompanied by pain and limited range of motion. Although arthrocentesis and aspiration might relieve the patient of some pain and improve range of motion initially, there are no evidence-based recommendations for this procedure. Therefore, unless there is clinical suspicion of infection the decision for arthrocentesis should be made individually under careful consideration of risks and benefits (14).

Non-contact injuries have historically been reported as the overall most common mechanism for ACL injury (15). However, there is some conflicting data reporting contact mechanisms being responsible for about 60% of ACL injuries in male athletes for instance (4). Subgroup analysis of different sport types likely provides different distribution patterns of injury mechanisms. Common movement patterns and forces that cause an ACL tear are quick decelerating motions during landing with the knee close to extension or hyperextension and a valgus moment with internal tibial rotation in flexion (16-19). Landing in a position with the knee near extension or hyperextension causes an eccentric activation of the quadriceps producing strong anterior translational forces (16), whereas a valgus collapse increases loads on the ACL during flexion (17,18).

Clinical tests

Several clinical tests are used to diagnose ACL injuries, with the anterior drawer test (ADT), Lachman test, and pivot-shift test being the most common (20). It should be noted that these tests are all manually performed by the examiner and evaluated based on the examiners subjective feeling of laxity. The degree of laxity is therefore determined qualitatively. According to the literature, the Lachman has the highest sensitivity, especially in acute cases, and is best in ruling out an ACL injury. The ADT has better accuracy in chronic ACL deficiency. Overall specificity is highest in the pivot-shift test, making it useful for ruling out an ACL injury (21,22). One meta-analysis investigated isolated ACL injuries only and reported a slightly lower but still acceptable sensitivity of the Lachman than previously reported (23). In partial injuries, the ADT is more likely to be positive for anteromedial bundle tears, while the Lachman test is more sensitive for posterolateral bundle injuries, which are also more likely to cause anterolateral rotatory instability and a positive pivot-shift. This is most likely caused by the difference in tension of the bundles depending on the degree of knee flexion (24).

Kocher et al. (25) compared the postoperative results of instrumented anterior laxity, pivot-shift examination and Lachman test with subjective outcomes in 202 patients. Their results showed that the pivot-shift test correlates significantly stronger with subjective outcomes than the Lachman or instrumented anterior laxity and concluded that the pivot-shift test might be the best choice to accurately follow up on patients after an ACL reconstruction.

GJL and knee hyperextension

GJL and knee hyperextension are likely important risk factors for primary ACL injury as well as ACL reconstruction failure (26). According to Zsidai et al. (27) patients with higher GJL who return to sports within the first 12 months have five times greater odds of re-injury. The Beighton and Horan criteria are used to measure GJL and consist of 5 different quantitative measurements providing a numerical score of 0–5 (28). A minimum of four points (29,30) and knee hyperextension >10° (5,30) have been associated with higher risk of ACL injury and increased laxity after ACL reconstruction.. Isolated knee hyperextension might be a more accurate predictor of outcome than the severity of GJL measured by a modified Beighton score (30). Another study suggested that heel height >5 cm and fifth metacarpophalangeal extension >90° can be used as predictors of graft failure and poor outcome (31).

Recently, Helito et al. (32) proposed that 6.5° knee hyperextension could be a significant cut off value with an odds ratio of 14.65 for a re-tear. In patients with excessive knee hyperextension a reconstruction with a bone-patellar tendon-bone or quadriceps tendon with bone autograft might have favourable stability and clinical outcomes compared to hamstring autografts (30,33). Adding an extra-articular procedure could also improve stability and outcome although there is lacking data regarding the long term outcome and more thorough evidence is needed to further prove these hypotheses (34). In general, there is common ground in the literature that either GJL or isolated laxity of the knee in terms of excessive hyperextension is a risk factor for graft failure. However, there currently are discrepancies in how the laxity should be defined and what degree of laxity or hyperextension makes a prognostic and therapeutical difference, increasing the need for further research in this field.

Imaging

Radiographs

Standard anterior-posterior and lateral radiographs of the knee are indispensable to rule out fractures or dislocations that require immediate care (35). Additionally, indirect signs of an ACL tear can be seen on standard radiographs. The anterior subluxation of the tibia in stress radiographs can be indicative of an insufficient ACL. The average increase in anterior translation in stress radiographs in ACL deficient patients is approximately 4.9 mm compared to the healthy side (36). Another indirect sign is a cortical avulsion fracture of the anterolateral portion of the tibia, also known as “Segond-Fracture” (37). A recent systematic review has shown that an unrepaired Segond fracture does not appear to have any significant negative effect on postoperative stability, risk of graft failure or revision surgery after ACL-reconstruction (38).

PTS

Radiographs are crucial not only for ruling out fractures but also for evaluating bony morphology and lower extremity alignment. Multiple meta-analyses have suggested that a higher medial and/or lateral PTS is associated with an increased risk of both primary ACL injury and re-injury after reconstruction (9,39). Biomechanical analysis of knee cadavers has demonstrated that the forces on the ACL increase linearly with a higher PTS (40). A radiographic PTS ≥12° is often considered the critical high risk cut-off value (41). In these cases, additional procedures such as anterior closing wedge-high tibial osteotomy (ACW-HTO) or lateral extra-articular tenodesis (LET) have shown promising clinical results, particularly in revision cases (42-45). Nevertheless, reports on return to sports rates are discrepant. In some studies, many patients can successfully return to pre-injury activity levels (43,44), while others experience less success (42,45). These reports should be interpreted with caution due to the low case numbers in most studies.

Currently, no single method for reliably measuring PTS has been universally agreed upon. Radiographic methods require a standard lateral view of the knee and can be acquired quickly with low cost (46,47) (Figure 1). A recent publication by Weiler et al. (41) found that lateral radiographs provide high intra- and interobserver reliability. The use of longer lateral X-rays with up to 20 cm tibial length might provide superior accuracy over standard lateral views (48). However, the accuracy of two-dimensional (2D) imaging can be compromised by malrotation (47). Computer tomography (CT) and magnetic resonance imaging (MRI) are potentially favourable in measuring medial and lateral slope separately compared to radiographs (49,50). Although there is a certain degree of correlation between radiographic PTS measurements and CT/MRI, high variability in all measurement modalities warrant caution when interpreting such measurements (51).

Figure 1 PTS measurement. Measurement of the PTS as described by Dejour and Bonnin (46) using a lateral plain radiograph. The diaphyseal tibial axis (c) is defined as the connection between the midpoints of two lines connecting the anterior and posterior border of the tibia shortly under the tibial tubercle (a) and 10 cm further below (b). A reference line (d) is drawn perpendicular at the connection of line c with the tibiofemoral joint. Another line is drawn between the most superior points of the anterior and posterior border of the medial tibia. The PTS is the angle between line d and e (α). PTS, posterior tibial slope.

Coronal alignment

In addition to the standard radiographs, a full weight-bearing bilateral long-leg X-ray is needed to determine the mechanical alignment of the knee and a Rosenberg-view is recommended to evaluate the joint space (52,53). Biomechanical research has shown that an increased varus-alignment leads to increased tension in the native ACL (54). The strain caused on the ACL by varus-malalignment alone is most likely not sufficient enough to cause an acute ACL tear but can be responsible for chronic ACL failure, in which case a correction osteotomy might be considered (54,55).

HTO combined with ACL reconstruction is a safe procedure with favourable clinical outcomes in cases of chronic ACL deficiency and early medial osteoarthritis (55,56). It can slow down the progression of osteoarthritis in young, active patients and reduce pain. However, in the elite athlete we must often deal with acute injuries and mechanically high demanding knees. Kim et al. (57) have suggested that adding a valgus-HTO to a primary ACL reconstruction in a varus-knee without signs of osteoarthritis does not lead to better clinical outcomes. The aims of HTO are to increase quality in daily life and work as well as slow the progression of osteoarthritis. Most studies that analysed return to sports after valgus HTO report acceptable participation in moderate sports but very low return to competitive or preinjury level of sports (58-61).

MRI

Suspicion of an ACL injury arises from a proper clinical examination. Due to its high diagnostic accuracy (62), an MRI is recommended to confirm diagnosis and reveal concomitant injuries of the menisci, cartilage and ligaments (Figure 2) (35). ACL injuries can be accompanied by bone bruises, which can be visualised as high-intensity signals in T2-weighted images or short tau inversion recovery sequences (63). The lateral femoral condyle and the posterior aspect of the lateral tibial plateau are the most common bone bruise locations in ACL injury and are associated with pivot-shifting or valgus-induced trauma (64). Medial compartment bone bruises can also occur but are more seldom. Some authors have described associations between medial posterior tibial bone bruises and medial meniscal ramp lesions (65,66). Past research has tried to link bone bruises to clinical outcomes or progression of osteoarthritis, however, this relation has not been fully understood and remains a topic of investigation (67).

Figure 2 ACL on the MRI. Comparison of two sagittal T2-weighted MRI images. (A) Continuous, intact ACL-fibres (arrows) can be detected. (B) No intact ACL fibres visible (arrowheads), suggesting ACL tear. ACL, anterior cruciate ligament; MRI, magnetic resonance imaging.

Another use of the MRI is the ability to plan an anatomical ACL reconstruction preoperatively. The femoral and tibial insertion sites of the ACL vary greatly in size between different patients (10). Since the goal is to restore the native ACL, attention should be given to the patients’ individual ACL morphology. Therefore, the decision which graft to harvest and what reconstruction technique to use also depends on the athletes’ anatomical prerequisites (11). Guenther et al. (68) demonstrated how MRI images can be used to measure the size of the tibial insertion with high accuracy and test-retest reliability. According to Fujimaki et al. (69) the cross-sectional area of the mid-substance ACL measures approximately 50% of the tibial insertion site. Based on their data it was proposed that graft size should be in the range of 50–80% of the tibial insertion to best match the mid-substance. Measuring cross-sectional areas of potential grafts is also possible with the MRI making it potentially useful for individualised graft choice (70). These findings underline that decision making should always be made individually for every patient as there is no singular graft or reconstruction technique that fits all sizes.

CT

Slope asymmetry with high lateral slope is associated with higher preoperative pivot-shift (71) and early ACL graft failure (72), while a shallow medial tibial plateau might be a risk factor for ACL injury (73). With a three-dimensional (3D) reconstructed CT image, the malrotation error of plain radiographs can be reduced, which increases the reliability in assessing tibial plateau morphology, however ethical concerns arise due to high radiation doses (74).

Tunnel malposition is considered a major risk factor for ACL reconstruction failure and has been associated with increased numbers of revision ACL surgery (75,76). Tunnel enlargement and/or coalition is a known phenomenon after ACL reconstruction (77,78). While the clinical implications of tunnel enlargement are probably not pivotal, it might cause problems in revision surgery regarding graft placement and fixation (79).

In summary, review of the current literature suggests that a CT scan is not necessarily needed in primary ACL injury. However, it is recommended in revision cases to properly assess the positioning and condition of the tunnels and adjust the surgical technique to achieve anatomical reconstruction.

Instrumented laxity measurement

Anterior laxity

Instrumented laxity measurement systems are objective tools to quantitatively assess the grade of laxity. In addition to the diagnostic value, the aim is to produce objective ordinal data that can be used for research and assist in making treatment decisions. Several studies suggest that higher anterior tibial translation is a risk factor for graft failure and increases odds of revision ACL surgery (80,81). Many different systems have been developed over the past decades to quantify anterior laxity. The most used is the KT-1000 (and 2000) arthrometer. Other known systems are the Genucom Knee Analysis System, Stryker Knee Laxity Tester, Rolimeter, Telos stress radiograph, Edixhoven Mechanic Lachman, Dyonics Dynamic Cruciate Tester and the Acufex Knee Signature System (82).

In 2009, Pugh et al. (83) published a systematic review which stated that the KT-1000 and Rolimeter are the most accurate and reliable systems to quantitatively measure anterior laxity of the knee. Although values for the diagnostic accuracy were provided, no statement could be made regarding the value of these systems in assessing postoperative outcome or implications for treatment decisions. According to this review the diagnostic accuracy is not superior to the traditional clinical examination. The authors suggest that the utility of these systems mostly remains in the research field rather than in the clinical setting.

Van Eck et al. (82) published a meta-analysis which identified sensitivity and specificity of the KT 1000 Arthrometer at maximum manual force to be 93% and 93% respectively. At 69N and 89N the sensitivity was 54% and 78%. This indicates that diagnostically valuable measurements can only be acquired with maximum manual force, however the force can vary between physicians. With regards to the elite athlete, it should also be noted that none of the studies provided subgroup analysis of the activity level. It appears that a gold standard for instrumented laxity measurement cannot be justified with the current data. Anterior laxity measurement systems can provide useful data for research as they produce comparable ordinal values but treatment decisions and recommendations for returning to sports should not be based solely on instrumented laxity measurements.

Anterolateral laxity/quantifying the pivot-shift test

Rotational laxity is caused by excessive translation of either the medial or lateral compartment leading to an abnormal, rotational motion of the tibia. This is also referred to as anteromedial or anterolateral laxity/instability (84). Dynamic anterolateral instability has gained a lot of interest in recent years for a couple of reasons. Firstly, preoperative excessive pivot-shift caused by injuries of the anterolateral ligament or posterolateral corner is associated with worse outcome (5). Secondly, the postoperative residual pivot-shift strongly correlates with subjective and objective outcome measures after ACL reconstruction (7,25). Furthermore, recent research has shown that addition of an extra-lateral procedure such as an LET in patients with severe rotational laxity and desire to return to high-risk sports can significantly reduce the graft failure rate and increase stability (85). This is important for elite athletes because of the high rotatory loads on their knees, especially in pivoting sports. However, it should be noted that long term results after ACL reconstruction with LET are currently lacking and further research is needed to analyse the longevity of this procedure.

Many attempts have been made to establish systems that can quantify rotational laxity or kinematics during a pivot-shift. The geometrical basis to describe tibial motion in relation to the femur on a 3D coordinate system requires movement and measurement of six independent degrees of freedom: flexion, abduction, rotation, distraction, anterior translation and lateral shift (86).

Electromagnetic measurement system (EMS)

In 2007 a non-invasive EMS has been introduced, which creates a 3D coordinate system using tracking sensors on straps mounted on the leg (87) (Figure 3). The results of the measurement can be visualized and analysed on a graphic user interface (Figure 4).

Figure 3 EMS setup. Medial view (A) and lateral view (B) of a pivot-shift measurement using a non-invasive EMS. Tracking sensors (star) on the thigh and lower limb are utilized for live measurement. EMS, electromagnetic measurement system.

Figure 4 Quantitative analysis of the pivot shift using EMS. Graphic user interface of the EMS with graphs visualizing anteroposterior translation of the tibia (mm) and acceleration (m/s²) over time (s). The occurrence of a pivot-shift phenomenon (sudden posterior reduction of proximal tibia) can be identified by finding steep descending translation curves (arrows). The acceleration curve is calculated by second derivative of translation (arrowheads). EMS, electromagnetic measurement system.

With this system, Hoshino et al. (88) further explored the dynamic nature of the pivot-shift by calculating posterior tibial acceleration. Their findings showed a significant correlation between acceleration and clinical grading. Nagai et al. (89) measured increased posterior tibial acceleration in ACL deficient knees which decreased significantly after successful ACL reconstruction. These findings suggest that acceleration might be a more clinically meaningful parameter of rotational laxity than others.

Accelerometer

Lopomo et al. (90) used a triaxial accelerometer mounted between the tibial tuberosity and Gerdy’s tubercle along the mechanical axis of the lateral compartment and were able to measure significant differences in acceleration between ACL injured knees compared to the corresponding healthy limb. Recently, Vaidya et al. (91) established a method which uses a smartphone as a substitute for an expensive accelerometer.

Video analysis software

Hoshino et al. (92) describe a digital camera-assisted method with stickers marking the lateral femoral epicondyle, Gerdy’s tubercle and the fibula head as anatomical landmarks to measure lateral tibial translation over time. To further increase availability and ease of use, there have been promising attempts of developing applications for tablets such as the iPad (93). However, in a comparison of three different non-invasive measurement systems (Accelerometer, iPad video analysis, EMS) the EMS showed superior accuracy (94).

Computer navigational system

Some research groups utilized computer navigational systems intraoperatively. Lane et al. (95) defined the “angle of P” which is a distinct shaped curve created by the arc of motion while the tibia is subluxated during the pivot-shift, compared to the reference flexion and extension arc of motion. The angle of P had the strongest correlation to the clinical grading of the pivot-shift in their analysis.

In conclusion, there here have been many innovative ideas to establish tools that can quantify the pivot-shift test over the past two decades. One big difficulty is the fact that performing a pivot-shift test often heavily relies on the examiner, but standardizing the pivot-shift test manoeuvre has been shown to provide a more consistent quantitative evaluation and may be helpful in designing future multi-centre clinical outcome trials (96).

Limitations

Several limitations need to be mentioned in this review. The selection and review of articles was done by a single author. Because the search was performed in one database only, there might be selection bias. This review focusses mainly on the ACL itself and does not include a large amount of information regarding concomitant intra- or extra-articular injuries of the knee.

Conclusions

ACL injuries remain a challenge for orthopaedic surgeons especially in athletes due to high demands on their knees and the aim of returning to the preinjury activity level. Diagnosis needs to be made precisely, and treatment planned carefully. Clinical tests such as the Lachman, ADT or manual pivot-shift test are based on the examiners subjective feeling and deliver qualitative results. The Lachman test has high sensitivity while the pivot-shift test shows high specificity. GJL and knee hyperextension are considered risk factors and might be addressed by graft choice or extra-articular procedures. Radiographs are recommended to rule out fractures, and a radiographic PTS >12° is considered a risk factor for ACL graft failure. MRI is recommended to confirm diagnosis, rule out concomitant injures and plan anatomical reconstruction. Many instrumented anterior laxity measurement systems have been developed. These systems aim to quantify the degree of anterior laxity. However, they do not provide superior accuracy in diagnosing an ACL injury compared to the standard clinical tests. The pivot-shift test is a crucial risk factor for ACL graft failure and one of the most important tests to assess anterolateral rotatory instability before and after ACL reconstruction. Many attempts have been made to establish simple and reliable quantification methods. It remains a challenging task, especially due to the dynamic nature of the pivot-shift test. Randomised controlled trials with large cohorts and multi-centre studies might provide more information about the reliability, accuracy and validity of these tools in the future and help determine a gold-standard.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editors (Jeremy Burnham, Brian Godshaw and Patrick Cook) for the series “Evaluation and Treatment of ACL Injuries in High Level Athletes: The Continuum of Care” published in Annals of Joint. The article has undergone external peer review.

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://aoj.amegroups.com/article/view/10.21037/aoj-25-40/rc

Peer Review File: Available at https://aoj.amegroups.com/article/view/10.21037/aoj-25-40/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://aoj.amegroups.com/article/view/10.21037/aoj-25-40/coif). The series “Evaluation and Treatment of ACL Injuries in High Level Athletes: The Continuum of Care” was commissioned by the editorial office without any funding or sponsorship. Y.H. serves as an unpaid editorial board member of Annals of Joint from December 2024 to December 2026. T.M. serves as an unpaid editorial board member of Annals of Joint from August 2024 to December 2026. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Written informed consent was obtained from the patient for the publication of this article and accompanying images.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Manojlovic M, Ninkovic S, Matic R, et al. Return to Play and Performance After Anterior Cruciate Ligament Reconstruction in Soccer Players: A Systematic Review of Recent Evidence. Sports Med 2024;54:2097-108. [Crossref] [PubMed]
2. Ross BJ, Savage-Elliott I, Brown SM, et al. Return to Play and Performance After Primary ACL Reconstruction in American Football Players: A Systematic Review. Orthop J Sports Med 2020;8:2325967120959654. [Crossref] [PubMed]
3. Gornitzky AL, Lott A, Yellin JL, et al. Sport-Specific Yearly Risk and Incidence of Anterior Cruciate Ligament Tears in High School Athletes: A Systematic Review and Meta-analysis. Am J Sports Med 2016;44:2716-23. [Crossref] [PubMed]
4. Agel J, Rockwood T, Klossner D. Collegiate ACL Injury Rates Across 15 Sports: National Collegiate Athletic Association Injury Surveillance System Data Update (2004-2005 Through 2012-2013). Clin J Sport Med 2016;26:518-23. [Crossref] [PubMed]
5. Ueki H, Nakagawa Y, Ohara T, et al. Risk factors for residual pivot shift after anterior cruciate ligament reconstruction: data from the MAKS group. Knee Surg Sports Traumatol Arthrosc 2018;26:3724-30. [Crossref] [PubMed]
6. Musahl V, Rahnemai-Azar AA, Costello J, et al. The Influence of Meniscal and Anterolateral Capsular Injury on Knee Laxity in Patients With Anterior Cruciate Ligament Injuries. Am J Sports Med 2016;44:3126-31. [Crossref] [PubMed]
7. Ayeni OR, Chahal M, Tran MN, et al. Pivot shift as an outcome measure for ACL reconstruction: a systematic review. Knee Surg Sports Traumatol Arthrosc 2012;20:767-77.
8. Hoshino Y, Miyaji N, Nishida K, et al. The concomitant lateral meniscus injury increased the pivot shift in the anterior cruciate ligament-injured knee. Knee Surg Sports Traumatol Arthrosc 2019;27:646-51. [Crossref] [PubMed]
9. Wang YL, Yang T, Zeng C, et al. Association Between Tibial Plateau Slopes and Anterior Cruciate Ligament Injury: A Meta-analysis. Arthroscopy 2017;33:1248-1259.e4. [Crossref] [PubMed]
10. Kopf S, Pombo MW, Szczodry M, et al. Size variability of the human anterior cruciate ligament insertion sites. Am J Sports Med 2011;39:108-13. [Crossref] [PubMed]
11. Rahnemai-Azar AA, Sabzevari S, Irarrázaval S, et al. Anatomical Individualized ACL Reconstruction. Arch Bone Jt Surg 2016;4:291-7.
12. Logerstedt DS, Snyder-Mackler L, Ritter RC, et al. Knee stability and movement coordination impairments: knee ligament sprain. J Orthop Sports Phys Ther 2010;40:A1-A37. [Crossref] [PubMed]
13. DeHaven KE. Diagnosis of acute knee injuries with hemarthrosis. Am J Sports Med 1980;8:9-14. [Crossref] [PubMed]
14. Brophy RH, Lowry KJ. American Academy of Orthopaedic Surgeons Clinical Practice Guideline Summary: Management of Anterior Cruciate Ligament Injuries. J Am Acad Orthop Surg 2023;31:531-7. [Crossref] [PubMed]
15. Arendt E, Dick R. Knee injury patterns among men and women in collegiate basketball and soccer. NCAA data and review of literature. Am J Sports Med 1995;23:694-701. [Crossref] [PubMed]
16. Boden BP, Dean GS, Feagin JA Jr, et al. Mechanisms of anterior cruciate ligament injury. Orthopedics 2000;23:573-8. [Crossref] [PubMed]
17. Markolf KL, Burchfield DM, Shapiro MM, et al. Combined knee loading states that generate high anterior cruciate ligament forces. J Orthop Res 1995;13:930-5. [Crossref] [PubMed]
18. Krosshaug T, Nakamae A, Boden BP, et al. Mechanisms of anterior cruciate ligament injury in basketball: video analysis of 39 cases. Am J Sports Med 2007;35:359-67. [Crossref] [PubMed]
19. Koga H, Nakamae A, Shima Y, et al. Mechanisms for noncontact anterior cruciate ligament injuries: knee joint kinematics in 10 injury situations from female team handball and basketball. Am J Sports Med 2010;38:2218-25. [Crossref] [PubMed]
20. Malanga GA, Andrus S, Nadler SF, et al. Physical examination of the knee: a review of the original test description and scientific validity of common orthopedic tests. Arch Phys Med Rehabil 2003;84:592-603. [Crossref] [PubMed]
21. Benjaminse A, Gokeler A, van der Schans CP. Clinical diagnosis of an anterior cruciate ligament rupture: a meta-analysis. J Orthop Sports Phys Ther 2006;36:267-88. [Crossref] [PubMed]
22. van Eck CF, van den Bekerom MP, Fu FH, et al. Methods to diagnose acute anterior cruciate ligament rupture: a meta-analysis of physical examinations with and without anaesthesia. Knee Surg Sports Traumatol Arthrosc 2013;21:1895-903. [Crossref] [PubMed]
23. Sokal PA, Norris R, Maddox TW, et al. The diagnostic accuracy of clinical tests for anterior cruciate ligament tears are comparable but the Lachman test has been previously overestimated: a systematic review and meta-analysis. Knee Surg Sports Traumatol Arthrosc 2022;30:3287-303. [Crossref] [PubMed]
24. Petersen W, Zantop T. Partial rupture of the anterior cruciate ligament. Arthroscopy 2006;22:1143-5. [Crossref] [PubMed]
25. Kocher MS, Steadman JR, Briggs KK, et al. Relationships between objective assessment of ligament stability and subjective assessment of symptoms and function after anterior cruciate ligament reconstruction. Am J Sports Med 2004;32:629-34. [Crossref] [PubMed]
26. Sundemo D, Hamrin Senorski E, Karlsson L, et al. Generalised joint hypermobility increases ACL injury risk and is associated with inferior outcome after ACL reconstruction: a systematic review. BMJ Open Sport Exerc Med 2019;5:e000620. [Crossref] [PubMed]
27. Zsidai B, Piussi R, Thomeé R, et al. Generalised joint hypermobility leads to increased odds of sustaining a second ACL injury within 12 months of return to sport after ACL reconstruction. Br J Sports Med 2023;57:972-8. [Crossref] [PubMed]
28. Beighton P, Horan F. Orthopaedic aspects of the Ehlers-Danlos syndrome. J Bone Joint Surg Br 1969;51:444-53.
29. Akhtar MA, Bhattacharya R, Keating JF. Generalised ligamentous laxity and revision ACL surgery: Is there a relation? Knee 2016;23:1148-53. [Crossref] [PubMed]
30. Kim SJ, Moon HK, Kim SG, et al. Does severity or specific joint laxity influence clinical outcomes of anterior cruciate ligament reconstruction? Clin Orthop Relat Res 2010;468:1136-41. [Crossref] [PubMed]
31. Larson CM, Bedi A, Dietrich ME, et al. Generalized Hypermobility, Knee Hyperextension, and Outcomes After Anterior Cruciate Ligament Reconstruction: Prospective, Case-Control Study With Mean 6 Years Follow-up. Arthroscopy 2017;33:1852-8. [Crossref] [PubMed]
32. Helito CP, da Silva AGM, Sobrado MF, et al. Patients With More Than 6.5° of Knee Hyperextension are 14.6 Times More Likely to Have Anterior Cruciate Ligament Hamstring Graft Rupture and Worse Knee Stability and Functional Outcomes. Arthroscopy 2024;40:898-907. [Crossref] [PubMed]
33. Yamasaki S, Hashimoto Y, Iida K, et al. Quadriceps Tendon With Bone Autograft Has Better Stability and Magnetic Resonance Imaging Maturation Than Hamstring Tendon Autograft After Anterior Cruciate Ligament Reconstruction in Patients With Knee Hyperextension. Arthroscopy 2024;40:1234-44. [Crossref] [PubMed]
34. Helito CP, Sobrado MF, Giglio PN, et al. Combined Reconstruction of the Anterolateral Ligament in Patients With Anterior Cruciate Ligament Injury and Ligamentous Hyperlaxity Leads to Better Clinical Stability and a Lower Failure Rate Than Isolated Anterior Cruciate Ligament Reconstruction. Arthroscopy 2019;35:2648-54. [Crossref] [PubMed]
35. Shea KG, Carey JL, Richmond J, et al. The American Academy of Orthopaedic Surgeons evidence-based guideline on management of anterior cruciate ligament injuries. J Bone Joint Surg Am 2015;97:672-4. [Crossref] [PubMed]
36. Mabrouk A, Olson CP, Tagliero AJ, et al. Reference standards for stress radiography measurements in knee ligament injury and instability: a systematic review. Knee Surg Sports Traumatol Arthrosc 2023;31:5721-46. [Crossref] [PubMed]
37. Dietz GW, Wilcox DM, Montgomery JB. Segond tibial condyle fracture: lateral capsular ligament avulsion. Radiology 1986;159:467-9. [Crossref] [PubMed]
38. Nagai K, Kamada K, Kay J, et al. Clinical Outcomes After Anterior Cruciate Ligament Reconstruction in Patients With a Concomitant Segond Fracture: A Systematic Review. Am J Sports Med 2023;51:525-33. [Crossref] [PubMed]
39. Duerr R, Ormseth B, Adelstein J, et al. Elevated Posterior Tibial Slope Is Associated With Anterior Cruciate Ligament Reconstruction Failures: A Systematic Review and Meta-analysis. Arthroscopy 2023;39:1299-1309.e6. [Crossref] [PubMed]
40. Bernhardson AS, Aman ZS, Dornan GJ, et al. Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases. Am J Sports Med 2019;47:296-302. [Crossref] [PubMed]
41. Weiler A, Berndt R, Wagner M, et al. Tibial Slope on Conventional Lateral Radiographs in Anterior Cruciate Ligament-Injured and Intact Knees: Mean Value and Outliers. Am J Sports Med 2023;51:2285-90. [Crossref] [PubMed]
42. Akoto R, Alm L, Drenck TC, et al. Slope-Correction Osteotomy with Lateral Extra-articular Tenodesis and Revision Anterior Cruciate Ligament Reconstruction Is Highly Effective in Treating High-Grade Anterior Knee Laxity. Am J Sports Med 2020;48:3478-85. [Crossref] [PubMed]
43. Sonnery-Cottet B, Mogos S, Thaunat M, et al. Proximal Tibial Anterior Closing Wedge Osteotomy in Repeat Revision of Anterior Cruciate Ligament Reconstruction. Am J Sports Med 2014;42:1873-80. [Crossref] [PubMed]
44. Song GY, Ni QK, Zheng T, et al. Slope-Reducing Tibial Osteotomy Combined With Primary Anterior Cruciate Ligament Reconstruction Produces Improved Knee Stability in Patients With Steep Posterior Tibial Slope, Excessive Anterior Tibial Subluxation in Extension, and Chronic Meniscal Posterior Horn Tears. Am J Sports Med 2020;48:3486-94. [Crossref] [PubMed]
45. Mabrouk A, Kley K, Jacquet C, et al. Outcomes of Slope-Reducing Proximal Tibial Osteotomy Combined With a Third Anterior Cruciate Ligament Reconstruction Procedure With a Focus on Return to Impact Sports. Am J Sports Med 2023;51:3454-63. [Crossref] [PubMed]
46. Dejour H, Bonnin M. Tibial translation after anterior cruciate ligament rupture. Two radiological tests compared. J Bone Joint Surg Br 1994;76:745-9.
47. Utzschneider S, Goettinger M, Weber P, et al. Development and validation of a new method for the radiologic measurement of the tibial slope. Knee Surg Sports Traumatol Arthrosc 2011;19:1643-8. [Crossref] [PubMed]
48. Faschingbauer M, Sgroi M, Juchems M, et al. Can the tibial slope be measured on lateral knee radiographs? Knee Surg Sports Traumatol Arthrosc 2014;22:3163-7. [Crossref] [PubMed]
49. Hudek R, Schmutz S, Regenfelder F, et al. Novel measurement technique of the tibial slope on conventional MRI. Clin Orthop Relat Res 2009;467:2066-72. [Crossref] [PubMed]
50. Akamatsu Y, Sotozawa M, Kobayashi H, et al. Usefulness of long tibial axis to measure medial tibial slope for opening wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2016;24:3661-7. [Crossref] [PubMed]
51. Naendrup JH, Drouven SF, Shaikh HS, et al. High variability of tibial slope measurement methods in daily clinical practice: Comparisons between measurements on lateral radiograph, magnetic resonance imaging, and computed tomography. Knee 2020;27:923-9. [Crossref] [PubMed]
52. Crawford MD, Diehl LH, Amendola A. Surgical Management and Treatment of the Anterior Cruciate Ligament-Deficient Knee with Malalignment. Clin Sports Med 2017;36:119-33. [Crossref] [PubMed]
53. Rosenberg TD, Paulos LE, Parker RD, et al. The forty-five-degree posteroanterior flexion weight-bearing radiograph of the knee. J Bone Joint Surg Am 1988;70:1479-83.
54. van de Pol GJ, Arnold MP, Verdonschot N, et al. Varus alignment leads to increased forces in the anterior cruciate ligament. Am J Sports Med 2009;37:481-7. [Crossref] [PubMed]
55. Tischer T, Paul J, Pape D, et al. The Impact of Osseous Malalignment and Realignment Procedures in Knee Ligament Surgery: A Systematic Review of the Clinical Evidence. Orthop J Sports Med 2017;5:2325967117697287. [Crossref] [PubMed]
56. Li Y, Zhang H, Zhang J, et al. Clinical outcome of simultaneous high tibial osteotomy and anterior cruciate ligament reconstruction for medial compartment osteoarthritis in young patients with anterior cruciate ligament-deficient knees: a systematic review. Arthroscopy 2015;31:507-19. [Crossref] [PubMed]
57. Kim SJ, Moon HK, Chun YM, et al. Is correctional osteotomy crucial in primary varus knees undergoing anterior cruciate ligament reconstruction? Clin Orthop Relat Res 2011;469:1421-6. [Crossref] [PubMed]
58. Dejour H, Neyret P, Boileau P, et al. Anterior cruciate reconstruction combined with valgus tibial osteotomy. Clin Orthop Relat Res 1994;220-8.
59. Bonin N, Ait Si Selmi T, Donell ST, et al. Anterior cruciate reconstruction combined with valgus upper tibial osteotomy: 12 years follow-up. Knee 2004;11:431-7. [Crossref] [PubMed]
60. Zaffagnini S, Bonanzinga T, Grassi A, et al. Combined ACL reconstruction and closing-wedge HTO for varus angulated ACL-deficient knees. Knee Surg Sports Traumatol Arthrosc 2013;21:934-41. [Crossref] [PubMed]
61. Trojani C, Elhor H, Carles M, et al. Anterior cruciate ligament reconstruction combined with valgus high tibial osteotomy allows return to sports. Orthop Traumatol Surg Res 2014;100:209-12. [Crossref] [PubMed]
62. Li K, Du J, Huang LX, et al. The diagnostic accuracy of magnetic resonance imaging for anterior cruciate ligament injury in comparison to arthroscopy: a meta-analysis. Sci Rep 2017;7:7583. [Crossref] [PubMed]
63. Filardo G, Andriolo L, di Laura Frattura G, et al. Bone bruise in anterior cruciate ligament rupture entails a more severe joint damage affecting joint degenerative progression. Knee Surg Sports Traumatol Arthrosc 2019;27:44-59. [Crossref] [PubMed]
64. Patel SA, Hageman J, Quatman CE, et al. Prevalence and location of bone bruises associated with anterior cruciate ligament injury and implications for mechanism of injury: a systematic review. Sports Med 2014;44:281-93. [Crossref] [PubMed]
65. Kim SH, Seo HJ, Seo DW, et al. Analysis of Risk Factors for Ramp Lesions Associated With Anterior Cruciate Ligament Injury. Am J Sports Med 2020;48:1673-81. [Crossref] [PubMed]
66. DePhillipo NN, Cinque ME, Chahla J, et al. Incidence and Detection of Meniscal Ramp Lesions on Magnetic Resonance Imaging in Patients With Anterior Cruciate Ligament Reconstruction. Am J Sports Med 2017;45:2233-7. [Crossref] [PubMed]
67. Ward P, Chang P, Radtke L, et al. Clinical Implications of Bone Bruise Patterns Accompanying Anterior Cruciate Ligament Tears. Sports Health 2022;14:585-91. [Crossref] [PubMed]
68. Guenther D, Irarrázaval S, Albers M, et al. Area of the tibial insertion site of the anterior cruciate ligament as a predictor for graft size. Knee Surg Sports Traumatol Arthrosc 2017;25:1576-82. [Crossref] [PubMed]
69. Fujimaki Y, Thorhauer E, Sasaki Y, et al. Quantitative In Situ Analysis of the Anterior Cruciate Ligament: Length, Midsubstance Cross-sectional Area, and Insertion Site Areas. Am J Sports Med 2016;44:118-25. [Crossref] [PubMed]
70. Offerhaus C, Albers M, Nagai K, et al. Individualized Anterior Cruciate Ligament Graft Matching: In Vivo Comparison of Cross-sectional Areas of Hamstring, Patellar, and Quadriceps Tendon Grafts and ACL Insertion Area. Am J Sports Med 2018;46:2646-52. [Crossref] [PubMed]
71. Kataoka K, Nagai K, Hoshino Y, et al. Steeper lateral posterior tibial slope and greater lateral-medial slope asymmetry correlate with greater preoperative pivot-shift in anterior cruciate ligament injury. J Exp Orthop 2022;9:117. [Crossref] [PubMed]
72. Christensen JJ, Krych AJ, Engasser WM, et al. Lateral Tibial Posterior Slope Is Increased in Patients With Early Graft Failure After Anterior Cruciate Ligament Reconstruction. Am J Sports Med 2015;43:2510-4. [Crossref] [PubMed]
73. Hashemi J, Chandrashekar N, Mansouri H, et al. Shallow medial tibial plateau and steep medial and lateral tibial slopes: new risk factors for anterior cruciate ligament injuries. Am J Sports Med 2010;38:54-62. [Crossref] [PubMed]
74. Zhang Y, Chen Y, Qiang M, et al. Comparison between three-dimensional CT and conventional radiography in proximal tibia morphology. Medicine (Baltimore) 2018;97:e11632. [Crossref] [PubMed]
75. Kamath GV, Redfern JC, Greis PE, et al. Revision anterior cruciate ligament reconstruction. Am J Sports Med 2011;39:199-217. [Crossref] [PubMed]
76. Shen X, Qin Y, Zuo J, et al. A Systematic Review of Risk Factors for Anterior Cruciate Ligament Reconstruction Failure. Int J Sports Med 2021;42:682-93. [Crossref] [PubMed]
77. Höher J, Möller HD, Fu FH. Bone tunnel enlargement after anterior cruciate ligament reconstruction: fact or fiction? Knee Surg Sports Traumatol Arthrosc 1998;6:231-40. [Crossref] [PubMed]
78. Nakanishi Y, Nagai K, Kay J, et al. The incidence of tibial tunnel coalition is higher than femoral tunnel coalition in double-bundle anterior cruciate ligament reconstruction using hamstring autografts: A systematic review. Orthop Traumatol Surg Res 2022;108:103407. [Crossref] [PubMed]
79. Iorio R, Vadalà A, Argento G, et al. Bone tunnel enlargement after ACL reconstruction using autologous hamstring tendons: a CT study. Int Orthop 2007;31:49-55. [Crossref] [PubMed]
80. Magnussen RA, Reinke EK, Huston LJ, et al. Effect of High-Grade Preoperative Knee Laxity on 6-Year Anterior Cruciate Ligament Reconstruction Outcomes. Am J Sports Med 2018;46:2865-72. [Crossref] [PubMed]
81. Cristiani R, Forssblad M, Engström B, et al. Risk Factors for Abnormal Anteroposterior Knee Laxity After Primary Anterior Cruciate Ligament Reconstruction. Arthroscopy 2018;34:2478-84. [Crossref] [PubMed]
82. van Eck CF, Loopik M, van den Bekerom MP, et al. Methods to diagnose acute anterior cruciate ligament rupture: a meta-analysis of instrumented knee laxity tests. Knee Surg Sports Traumatol Arthrosc 2013;21:1989-97. [Crossref] [PubMed]
83. Pugh L, Mascarenhas R, Arneja S, et al. Current concepts in instrumented knee-laxity testing. Am J Sports Med 2009;37:199-210. [Crossref] [PubMed]
84. Kurimura M, Matsumoto H, Fujikawa K, et al. Factors for the presence of anteromedial rotatory instability of the knee. J Orthop Sci 2004;9:380-5. [Crossref] [PubMed]
85. Getgood AMJ, Bryant DM, Litchfield R, et al. Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial. Am J Sports Med 2020;48:285-97. [Crossref] [PubMed]
86. Grood ES, Suntay WJ. A joint coordinate system for the clinical description of three-dimensional motions: application to the knee. J Biomech Eng 1983;105:136-44. [Crossref] [PubMed]
87. Kubo S, Muratsu H, Yoshiya S, et al. Reliability and usefulness of a new in vivo measurement system of the pivot shift. Clin Orthop Relat Res 2007;54-8. [Crossref] [PubMed]
88. Hoshino Y, Kuroda R, Nagamune K, et al. In vivo measurement of the pivot-shift test in the anterior cruciate ligament-deficient knee using an electromagnetic device. Am J Sports Med 2007;35:1098-104. [Crossref] [PubMed]
89. Nagai K, Hoshino Y, Nishizawa Y, et al. Quantitative comparison of the pivot shift test results before and after anterior cruciate ligament reconstruction by using the three-dimensional electromagnetic measurement system. Knee Surg Sports Traumatol Arthrosc 2015;23:2876-81. [Crossref] [PubMed]
90. Lopomo N, Zaffagnini S, Signorelli C, et al. An original clinical methodology for non-invasive assessment of pivot-shift test. Comput Methods Biomech Biomed Engin 2012;15:1323-8. [Crossref] [PubMed]
91. Vaidya RK, Yoo CW, Lee J, et al. Quantitative assessment of the pivot shift test with smartphone accelerometer. Knee Surg Sports Traumatol Arthrosc 2020;28:2494-501. [Crossref] [PubMed]
92. Hoshino Y, Araujo P, Irrgang JJ, et al. An image analysis method to quantify the lateral pivot shift test. Knee Surg Sports Traumatol Arthrosc 2012;20:703-7. [Crossref] [PubMed]
93. Hoshino Y, Araujo P, Ahldén M, et al. Quantitative evaluation of the pivot shift by image analysis using the iPad. Knee Surg Sports Traumatol Arthrosc 2013;21:975-80. [Crossref] [PubMed]
94. Tanaka T, Hoshino Y, Miyaji N, et al. The diagnostic reliability of the quantitative pivot-shift evaluation using an electromagnetic measurement system for anterior cruciate ligament deficiency was superior to those of the accelerometer and iPad image analysis. Knee Surg Sports Traumatol Arthrosc 2018;26:2835-40. [Crossref] [PubMed]
95. Lane CG, Warren RF, Stanford FC, et al. In vivo analysis of the pivot shift phenomenon during computer navigated ACL reconstruction. Knee Surg Sports Traumatol Arthrosc 2008;16:487-92. [Crossref] [PubMed]
96. Hoshino Y, Araujo P, Ahlden M, et al. Standardized pivot shift test improves measurement accuracy. Knee Surg Sports Traumatol Arthrosc 2012;20:732-6. [Crossref] [PubMed]