The role of muscle forces on rotational and cranio-caudal stability in the intact and CCL-deficient stifle: An ex vivo biomechanical study.

Muscle strengthening reduces rotational laxity but cannot prevent cranio-caudal translation; surgery remains necessary post-CCL rupture.

This ex vivo biomechanical study examined how muscle activation influences rotational and cranio-caudal stability in canine stifles, comparing intact joints with those deficient in the cranial cruciate ligament (CCL). Using eight cadaveric stifles, researchers simulated quadriceps, biceps femoris, and gastrocnemius muscle forces via pneumatic actuators at varying activation levels (0-100% bodyweight). Results demonstrated that without muscle activation, CCL transection significantly increased internal tibial rotation. However, progressive muscle activation substantially reduced internal rotation in both intact and CCL-deficient joints, with biceps femoris providing superior rotational control compared to quadriceps and gastrocnemius. Notably, muscle activation meaningfully reduced cranio-caudal translation in CCL-deficient stifles, though the deficient joints still exhibited substantially greater laxity (19.1 mm versus 2.8 mm at 100% activation). These findings suggest periarticular muscle strengthening can mitigate rotational instability but cannot adequately prevent cranio-caudal translation following CCL rupture, indicating that surgical stabilization remains essential for complete functional recovery.

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