Surface-based treatment options for cartilage lesions of the knee

Articular cartilage lesions of the knee pose a significant clinical challenge due to the limited regenerative capacity of hyaline cartilage and the wide variability in patient presentation and lesion characteristics. Surface-based cartilage restoration techniques have evolved substantially, shifting from isolated marrow stimulation toward biologically enhanced strategies designed to improve repair tissue quality, durability, and clinical outcomes while preserving native joint anatomy. These techniques are primarily indicated for contained chondral defects without substantial subchondral bone compromise and include scaffold-augmented microfracture, particulated cartilage techniques using juvenile or adult allograft tissue, and matrix-associated autologous chondrocyte implantation (ACI). Selection among these options is driven by patient age, activity level, and expectations, as well as lesion-specific factors such as size, anatomic location, containment, and subchondral bone integrity. Single-stage approaches, including micronized cartilage extracellular matrix augmentation and particulated cartilage allografts, offer reduced procedural burden and avoidance of cell expansion, with favorable short- to mid-term outcomes for small to moderate lesions. In contrast, matrix-induced autologous chondrocyte implantation (MACI) is supported by randomized controlled trials and long-term cohort studies demonstrating sustained improvements in patient-reported outcomes (PROs) beyond 10 years, particularly in younger, active patients with larger isolated defects. Despite these advances, variability in imaging findings, complication profiles, and performance in the patellofemoral joint underscores the importance of appropriate patient selection, meticulous surgical technique, and structured postoperative rehabilitation. This review synthesizes current evidence regarding indications, surgical techniques, outcomes, and limitations of contemporary surface-based cartilage restoration options for the knee, providing a practical framework to guide clinical decision-making in joint preservation surgery.