Arthroscopic cartilage indentation and cartilage lesions of anterior cruciate ligament-deficient knees

Background: The anterior cruciate ligament-deficient knee is prone to osteoarthritis and meniscus lesions. Very little, however, is known about the biomechanical properties of articular cartilage in anterior cruciate ligament-deficient knees. Purpose: To evaluate biomechanical and macroscopical cartilage changes in the knee joint with respect to the time after anterior cruciate ligament rupture. Hypothesis: Chronic anterior cruciate ligament deficiency induces cartilage softening. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Cartilage stiffness of 50 patients undergoing anterior cruciate ligament reconstructive surgery because of symptomatic knee instability after chronic anterior cruciate ligament rupture was measured with an arthroscopic indenter device, and the number and size of cartilage lesions were evaluated. Results: The cartilage stiffness did not correlate with time from trauma to surgery (r = 0.002, P = .99), but the number of cartilage lesions in the knee increased when the time from the initial trauma to reconstructive surgery increased (r = 0.356, P = .011). Indentation values measured on healthy-looking cartilage on damaged joint surfaces were lower than the values measured on healthy joint surfaces (P < .01 on lateral femoral condyle and on tibial plateaus). Conclusions: The number of cartilage lesions increases with increased time after initial trauma. The arthroscopic indenter device is able to detect cartilage softening as the early mechanical sign of degradation not yet visible to the eye.