AJSM - 2026-07-12 - Journal Article
Association of Early Knee Extension Range of Motion Deficits With Cartilage T2 Relaxation Following Anterior Cruciate Ligament Reconstruction.
Allison A, Harrington J, Weaver B, Manzer M, Sajja BR, Tao MA, Wellsandt E
Topics
Key Takeaway
Extension deficit >3° at 2 months post-ACLR is associated with 10.21% greater T2 increase in anterior medial femoral condyle cartilage and 6.14% greater increase in the weightbearing zone at 6 months.
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Summary
This study asked whether knee extension ROM deficit >3° at 2 months post-ACLR predicts early cartilage compositional changes measured by T2 relaxometry at 6 months. Thirty patients aged 15–35 underwent quantitative MRI pre-op and at 6 months; 50% had an extension deficit at 2 months. Those with deficits showed significantly greater T2 increases in the anterior (10.21%, P=.003) and weightbearing (6.14%, P=.004) medial femoral condyle, with no significant differences in other cartilage regions.
Key Limitation
T2 relaxation time elevation reflects cartilage water content and collagen disorganization but does not establish causality or predict whether these early compositional changes progress to clinically significant OA.
Original Abstract
BACKGROUND
Anterior cruciate ligament (ACL) injury significantly increases the risk for developing knee osteoarthritis (OA), yet the early contributors to cartilage degeneration remain poorly understood. While range of motion (ROM) deficits after ACL reconstruction (ACLR) are associated with long-term development of radiographic OA, the association between early ROM recovery and cartilage composition has not been established.
HYPOTHESIS
Knee extension ROM deficits at 2 months after ACLR would be associated with worsening tibiofemoral and patellofemoral cartilage T2 relaxation times at 6 months.
STUDY DESIGN
Cohort study; Level of evidence, 2.
METHODS
A total of 30 participants (15-35 years) were enrolled within 1 month of ACL injury and before ACLR. At 2 months post-ACLR, active knee extension ROM was measured in the supine position using a goniometer. An extension deficit was considered >3° less extension in the injured knee compared to the uninjured side. Quantitative magnetic resonance imaging-based T2 relaxometry of the injured knee was performed preoperatively and at 6 months post-ACLR to measure percent change in mean T2 relaxation times in predefined tibial and femoral cartilage regions. Independent t tests were used to compare changes in T2 values between participants with and without an extension deficit.
RESULTS
The mean age of the participants was 18.8 ± 3.9 years, and 63.3% were female. Fifteen (50.0%) participants exhibited an extension deficit at 2 months. Those with an extension deficit demonstrated a greater increase in T2 relaxation time in the anterior (mean difference, 10.21% [95% CI, 3.67%-16.76%]; P = .003) and weightbearing (mean difference, 6.14% [95% CI, 2.19%-10.09%]; P = .004) cartilage of the medial femoral condyle. No significant group differences were observed in other cartilage regions (all P > .05).
CONCLUSION
Knee extension ROM deficits at 2 months post-ACLR are associated with early compositional changes in the medial femoral cartilage, indicating a potential relationship between limited extension and OA risk.