All-arthroscopic release in treating knee stiffness after anterior cruciate ligament reconstruction

Introduction

Knee stiffness is a recognized complication after anterior cruciate ligament reconstruction (ACLR) and can compromise postoperative range of motion (ROM) and functional recovery (1,2). Despite advances in surgical techniques and rehabilitation protocols, some patients still develop postoperative stiffness after ACLR. Knee stiffness is one of the common complications following ACLR, with clinical studies indicating an occurrence rate of approximately 4% to 38% (3-6). The ROM deficit caused by knee stiffness has a significant impact on patients’ daily lives, leading to difficulties in activities such as squatting, limping, and even walking.

Conservative treatment for knee stiffness is often ineffective, making surgical intervention necessary. Various surgical techniques have been employed clinically, including Thompson quadricepsplasty, Judet quadricepsplasty, manipulation under anesthesia, and arthroscopic release (7,8).

However, the optimal surgical strategy for knee stiffness after ACLR remains uncertain. Prior studies are often limited by heterogeneous etiologies, variability in surgical techniques, and non-standardized postoperative rehabilitation protocols, which complicate comparisons across reports and limit the generalizability of their conclusions. Therefore, we aimed to evaluate the clinical effectiveness of a standardized all-arthroscopic release combined with a structured postoperative rehabilitation protocol in a homogeneous cohort of patients with knee stiffness following ACLR. This retrospective study included 40 patients with 12 months of follow-up. The primary aim was to quantify postoperative recovery of knee ROM over time (preoperatively, immediately postoperatively, and at 3, 6, and 12 months), and we hypothesized that ROM would improve significantly after surgery compared with preoperative values. Secondary aims were to assess functional outcomes using the Lysholm and Tegner scores (9-11) and to characterize procedure-related complications; we hypothesized that functional scores would improve and that the complication rate would be acceptably low. We present this article in accordance with the STROBE reporting checklist (available at https://aoj.amegroups.com/article/view/10.21037/aoj-2025-1-92/rc).

Methods

This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This retrospective study was approved by the Institutional Review Board of the Affiliated Hospital of Nanjing University of Chinese Medicine (approval No. YJZ202484). The requirement for written informed consent was waived due to the retrospective design and the use of fully de-identified data. All data were handled confidentially.

Inclusion and exclusion criteria

Inclusion criteria

• Age between 18 and 65 years;
• Patients diagnosed with postoperative knee stiffness after primary, isolated ACLR of the index knee;
• Persistent limitation of knee ROM after rehabilitation that interfered with activities of daily living, corresponding to an International Knee Documentation Committee (IKDC) (12) ROM grade of C or D;
• First-time all-arthroscopic release of the index knee;
• Complete and retrievable clinical medical records.

Exclusion criteria

• Revision ACLR and/or multi-ligament knee reconstruction;
• Knee stiffness due to rheumatoid arthritis, psoriatic arthritis, post-joint replacement surgery, fractures, or other causes;
• Prior release surgery of the index knee;
• Concomitant local active infection or systemic infection;
• Severe muscle atrophy of the affected limb;
• Peripheral nerve injury affecting lower limb function;
• Inability to comply with standardized postoperative rehabilitation;
• Individuals with contraindications to the perioperative medication regimen or severe medical comorbidities that precluded surgery or postoperative rehabilitation.

Surgical method

The patient was placed in the supine position under general anesthesia, and a pneumatic tourniquet was applied to the proximal third of the thigh. An adjustable lateral post and foot support were used to stabilize the operative knee. Preoperative knee ROM was measured and recorded (Figure 1). Subsequently, a mixed solution of 40 mL containing epinephrine (1:10,000) and 20 mL of 0.75% ropivacaine (total volume 60 mL) was injected into the joint cavity to reduce intraoperative bleeding. The surgical field was disinfected and draped. With the knee in extension, a standard anterolateral portal was established at the lateral edge of the patellar tendon at the level of the inferior pole of the patella. After blunt dilation, a cannula was inserted and a 30° arthroscope was introduced with saline irrigation. A standard anteromedial portal was then established under spinal-needle localization, and a radiofrequency device or shaver was inserted. Scar tissue between the cruciate ligaments and femoral condyles and at the anterior horns of the medial and lateral menisci was debrided to expose the tibial intercondylar eminences and femoral intercondylar notch. Through the anteromedial portal, the medial retinaculum and capsule were released toward the medial border of the vastus medialis at the adductor tubercle, and adhesions between the medial capsule and medial femoral condyle were cleared to recreate the medial gutter. Through the anterolateral portal, the lateral retinaculum and capsule were released toward the junction of the vastus lateralis and iliotibial band, and adhesions between the iliotibial band and lateral femoral condyle were removed to recreate the lateral gutter. The infrapatellar fat pad was separated from the inferior pole of the patella to access the patellofemoral joint, and release along the anterior aspect of the distal femur was performed to reconstruct the suprapatellar pouch. A superolateral portal was established under localization, and scar tissue within the suprapatellar pouch—particularly adhesions beneath the quadriceps tendon—was removed.

Figure 1 Flexion and extension angles of the knee joint in the same patient before surgery.

For patients with an extension deficit, posterior release was also performed. With the knee flexed to 30°, the cannula was advanced through the anterolateral portal across the intercondylar notch into the posteromedial compartment; a 30° arthroscope was introduced, and with the knee flexed to 90°, a posteromedial portal was established under spinal-needle localization. Scar tissue was removed to recreate the posteromedial compartment. After the arthroscope was transferred to the posteromedial portal for visualization, a blunt cannula was advanced through the posterior joint capsule to establish the posterolateral portal. Scar tissue was debrided to recreate the posterolateral compartment, followed by release of the posterior capsule from the posterior aspect of the distal femur and the fibrotic layers of the medial and lateral heads of the gastrocnemius (Figure 2).

Figure 2 Arthroscopic views: (A) ACL enveloped by scar tissue; (B) ACL after debridement; (C) suprapatellar pouch filled with scar tissue; (D) suprapatellar pouch after debridement; (E) posterior compartment of the knee filled with scar tissue; (F) posterior compartment after debridement. ACL, anterior cruciate ligament.

After intra-articular debridement and selective quadriceps release, manual manipulation was performed to break residual adhesions and achieve maximal flexion. Knee ROM was assessed and recorded (Figure 3). The joint was reentered for hemostasis and lavage with radiofrequency, followed by intra-articular injection of absorbable fluid gelatin for hemostasis. A silicone drain was placed through the anterolateral portal. The incisions were closed in layers, and sterile dressings with compression bandaging were applied.

Figure 3 Flexion and extension angles of the knee joint in the same patient after surgery.

Postoperative management

Postoperatively, routine ice-pack application was carried out, and cefazolin sodium was administered as prophylaxis against infection. For analgesia, flurbiprofen axetil injection and sustained-release tramadol hydrochloride tablets were used. Methylprednisolone acetate tablets were administered to relieve muscle tension, diosmin tablets for swelling, and intravenous dexamethasone sodium phosphate to reduce inflammatory exudation. Alendronate sodium tablets were prescribed to prevent osteoporosis, and indomethacin suppositories were administered to prevent heterotopic ossification (HO).

The steroid regimen postoperatively included intravenous dexamethasone immediately after surgery, continued for three days. Following the intravenous medication, a step-down oral treatment with prednisone acetate was initiated. The specifics are as follows: the initial dose was 10 mg, taken three times daily (tid) for three days; then the dose was adjusted to 5 mg, three times daily, maintained for three days; subsequently reduced to 5 mg once daily (qd) for five days; and finally tapered down to 2.5 mg once daily for 15 days, completing the entire withdrawal protocol.

Postoperative rehabilitation

Postoperative rehabilitation program: when the drainage volume is less than 400 mL within 24 hours postoperatively, the drainage tube is removed, and passive rehabilitation training is initiated 30 minutes afterward. The specific content is as follows:

• Continuous passive motion (CPM) machine-assisted training: the starting angle is 0°, with an ending angle of 90°, increasing by 5° daily. The training frequency is set at 1 cycle per minute, with a daily training duration of no less than 4 hours.
• Passive knee flexion ROM training: the patient is positioned in a prone position and gradually flexes the knee joint to the maximum angle, ultimately reaching the intraoperative flexion angle. Training is conducted twice daily for 15 minutes each time.
• Patellar mobility training: the patient maintains the knee joint in an extended position while the rehabilitation therapist performs internal and external patellar mobilizations. After pushing to the maximum extent, the patella is released, and the procedure is repeated. This training occurs twice daily for 15 minutes each session.
• Passive knee extension ROM training: postoperatively, patients are instructed to prepare a 5 kg sandbag (the weight can be adjusted according to the patient’s tolerance). The ankle joint of the affected limb is elevated using a soft cushion, allowing the knee joint to hang freely, after which the sandbag is placed above the knee to apply pressure. Training should be conducted at least 4 times daily for 30 minutes each time.

Additionally, within the first month of post-surgery, patients should use crutches for ambulation, avoiding weight-bearing on the affected limb to prevent postoperative hematoma organization, which could impact the rehabilitation process. Cold therapy should be promptly applied to the training site after each rehabilitation session.

Observation indicators

• Knee ROM was recorded immediately after surgery, with follow-up assessments conducted at 3, 6, and 12 months post-surgery to document the knee joint ROM and evaluate postoperative rehabilitation outcomes. ROM was measured clinically by manual assessment performed by the same trained orthopedic clinician at each follow-up visit; no goniometer was used.
• Postoperative knee function was assessed using the Tegner Activity Scale and the Lysholm knee score (9-11).
• Adverse complications were monitored and documented, including infection, recurrent stiffness, patellar tendon rupture, and clinically significant quadriceps weakness.

Statistical analysis

All data were analyzed using SPSS 27.0. Continuous variables are expressed as mean ± standard deviation. Normality was assessed graphically using normal P-P plots prior to parametric analyses. Changes in ROM across the perioperative time points were analyzed using repeated-measures analysis of variance (ANOVA), with time as the within-subject factor. Paired sample t-tests were used to compare the differences in Lysholm scores and Tegner scores between preoperative and postoperative assessments. A two-sided P value <0.05 was considered statistically significant.

Results

We retrospectively reviewed 40 consecutive patients who underwent all-arthroscopic release for knee stiffness after ACLR during the study period. No patients were excluded. All patients completed a 12-month follow-up. There were 19 females and 21 males, with a mean age of 32±6 years. All 40 patients had restricted knee flexion, and 32 also had an extension deficit. The previous surgical procedure in all cases was ACLR, and the indication for the current surgery was knee stiffness after ACLR. All procedures were performed using all-arthroscopic release.

Treatment outcomes

Repeated-measures ANOVA demonstrated a significant effect of time on knee flexion ROM (F=161.206, P<0.001). Post hoc pairwise comparisons versus the preoperative baseline [least significant difference (LSD) test; no adjustment for multiple comparisons] showed that flexion significantly increased from 78.50°±20.64° preoperatively to 125.75°±11.07° postoperatively (P<0.001), and remained significantly improved at 3 months (120.88°±10.80°, P<0.001), 6 months (126.00°±9.82°, P<0.001), and 12 months (131.75°±8.96°, P<0.001) (Table 1, Figure 4).

Figure 4 Knee joint flexion angle at different follow-up time points postoperatively. Data are presented as mean ± standard deviation. Intraop, intraoperative; m, month(s); Postop, postoperative; Preop, preoperative.

For extension deficit, repeated-measures ANOVA also showed a significant time effect (F=73.057, P<0.001). Post hoc comparisons versus the preoperative baseline (LSD test; no adjustment for multiple comparisons) indicated significant improvement from 8.38°±6.03° preoperatively to 1.70°±2.43° postoperatively (P<0.001), with further significant improvements at 3 months (1.17°±1.63°, P<0.001), 6 months (1.00°±1.41°, P<0.001), and 12 months (0.67°±1.07°, P<0.001) (Table 2, Figure 5).

Figure 5 Knee joint extension deficit angle at different follow-up time points postoperatively. Data are presented as mean ± standard deviation. Intraop, intraoperative; m, month(s); Postop, postoperative; Preop, preoperative.

In terms of functional scoring, the Lysholm score improved from 63.75±6.81 preoperatively to 85.92±6.10 at 12 months postoperatively (P<0.001). The Tegner score increased from 1.15±0.53 preoperatively to 4.82±0.87 at 12 months postoperatively (P<0.001) (Tables 3,4). These results highlight the significant improvement in patients’ mobility and quality of life following the surgery.

All patients completed follow-up (12 months). Postoperative observations indicated that all incisions achieved primary healing, and there were no occurrences of infection, recurrent stiffness, patellar tendon ruptures, or significant quadriceps muscle weakness during the follow-up period.

Discussion

In this study, all-arthroscopic arthrolysis for postoperative knee stiffness after ACLR significantly improved knee ROM and functional outcomes, with a low complication rate during follow-up.

There are several treatment options for knee stiffness, including rehabilitation therapy, manual release under anesthesia, and surgical intervention. Rehabilitation typically includes CPM, active strengthening, and physical therapy to promote capsular stretching and reduce scar formation. Nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce inflammation, and short-term intra-articular corticosteroid injections may help suppress excessive fibroblast proliferation. Regarding surgical management, traditional procedures such as Thompson and Judet quadricepsplasties can be effective but are invasive and associated with higher complication rates, including wound infection and skin necrosis (13-15). With advances in minimally invasive techniques, arthroscopic intra-articular release, mini-incision extra-articular release, and multilevel Z-lengthening of the quadriceps tendon have become increasingly adopted (16). Among these approaches, all-arthroscopic release is widely favored because it minimizes surgical trauma and bleeding, facilitates faster recovery, enables precise debridement of intra-articular fibrotic tissue, and is associated with less postoperative pain and fewer complications (17-23).

Our study showed that at the time of 3-month follow-up postoperatively, patients often exhibit a rebound phenomenon of ROM compared to the immediate postoperative effects. This phenomenon may be attributable to tissue remodeling during the first 1–3 months after surgery. During this stage, surgery-related intra-articular inflammation can promote fibrin exudation and increased collagen synthesis to repair damaged tissue (24-27). The resulting scar tissue may act as a “tightening rope”, increasing traction on periarticular soft tissues, contributing to capsular contracture and reduced ligament elasticity, and thereby mechanically limiting knee ROM. However, after 3 months, this rebound typically diminished as local edema subsided and inflammation decreased; in parallel, patients’ pain tolerance improved, enabling more active participation in rehabilitation exercises.

Notably, due to the complex anatomical structure of the posterior compartment, which includes important vessels like the popliteal vein, there is a risk of significant bleeding when cleaning this area. There are few surgeons who are adept at performing all-arthroscopic procedures for cleaning the posterior compartment of the knee. In this study, we performed thorough cleaning of the posterior compartment in 32 patients with knee extension limitations, and no vascular injuries occurred intraoperatively. During the procedure, selective release was performed on the quadriceps contraction areas using radiofrequency, complemented by manual release to overcome residual stiffness, thus achieving a multidimensional release effect. Preoperatively, the injection of a mixture containing epinephrine and ropivacaine into the joint cavity, alongside the postoperative application of absorbable fluid gelatin, effectively controlled intraoperative bleeding and postoperative edema (28,29), creating favorable conditions for early rehabilitation.

Postoperative functional rehabilitation is crucial for the outcome of all arthroscopic release surgery. Early rehabilitation helps prevent re-adhesion within the joint (19,30), which primarily includes passive movements, calf stretching exercises, and CPM. Passive mobilization can improve periarticular circulation, facilitate resorption of intra-articular fibrin, and reduce knee edema, thereby improving function and ROM. Accordingly, CPM and passive ROM should be initiated early after surgery to optimize restoration of joint mobility. In the later phase, rehabilitation should emphasize strengthening of the peri-knee musculature, which helps stretch contracted soft tissues and further improves flexion and extension. In addition, postoperative pharmacologic adjuncts may also contribute to improved outcomes. NSAIDs reduce vascular permeability, inhibit platelet aggregation and fibrinolysis, and suppress cyclooxygenase to lower prostaglandin synthesis, providing anti-adhesion, anti-inflammatory, and analgesic effects; they are commonly used for postoperative pain control and to prevent re-adhesion (31,32). Oral corticosteroids can reduce microvascular permeability, exudation, and fibroblast proliferation, helping alleviate inflammation and edema and prevent re-adhesion, though infection risk must be considered (33). Preventing HO is key after arthroscopic lysis, oral bisphosphonates and NSAIDs (first-line) can significantly reduce the HO incidence (34-37).

Limitations

This study has several limitations. First, its retrospective design and lack of a control or comparison group limit causal inference and preclude direct comparisons with alternative treatments. Second, the sample size was relatively small and follow-up duration was limited, reducing the ability to assess long-term outcomes. Third, adherence to the rehabilitation protocol was not objectively quantified in all patients, which may have influenced postoperative results. In addition, data on the incidence of postoperative complications and their potential risk factors were insufficient. Future studies should include larger cohorts with longer follow-up and, ideally, prospective multicenter controlled designs to better evaluate comparative effectiveness and to further refine surgical and rehabilitation protocols. Although the improvements in ROM and patient-reported outcomes in our cohort are broadly consistent with prior reports on arthroscopic release and other treatments for post-ACLR knee stiffness (23,38,39), direct comparisons require prospective controlled studies.

Conclusions

In summary, in this retrospective observational study without a control group, all-arthroscopic release for knee stiffness after ACLR was feasible, and no major safety concerns were observed in our cohort. Patients demonstrated improvements in knee ROM and functional scores at follow-up. Prospective controlled studies are warranted to confirm these findings and to compare outcomes with alternative treatments.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://aoj.amegroups.com/article/view/10.21037/aoj-2025-1-92/rc

Data Sharing Statement: Available at https://aoj.amegroups.com/article/view/10.21037/aoj-2025-1-92/dss

Peer Review File: Available at https://aoj.amegroups.com/article/view/10.21037/aoj-2025-1-92/prf

Funding: This work was supported by the National Natural Science Foundation of China (grant No. 82474537); Priority Disease Project of Jiangsu Province Hospital of Chinese Medicine (No. YZB2418); and Special Academic Advancement Program for Department Chiefs of Jiangsu Province Hospital of Chinese Medicine (No. Y2022ZR23).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://aoj.amegroups.com/article/view/10.21037/aoj-2025-1-92/coif). The authors report that this work was supported by the National Natural Science Foundation of China (grant No. 82474537); Priority Disease Project of Jiangsu Province Hospital of Chinese Medicine (No. YZB2418); and Special Academic Advancement Program for Department Chiefs of Jiangsu Province Hospital of Chinese Medicine (No. Y2022ZR23). 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. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This retrospective study was approved by the Institutional Review Board of Affiliated Hospital of Nanjing University of Chinese Medicine (approval No. YJZ202484). The requirement for written informed consent was waived due to the retrospective design and the use of fully de-identified data.

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/.

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