Femorotibial joint rotation in intact joints and following partial medial collateral ligament transection, tibial plateau leveling osteotomy, and cranial cruciate ligament transection - A limb press study.

Despite widespread use of tibial plateau leveling osteotomy (TPLO), the influence of partial medial collateral ligament transection (pMCLX) and physiologic loading on rotational stability remains unclear. This cadaveric study quantified internal and external tibial rotation in canine stifles under simulated weightbearing conditions. Ten unpaired pelvic limbs were mounted in a custom limb press applying axial loads equivalent to 30 % body weight with the stifle fixed at 135°. Quadriceps tension was simulated using a load cell and turnbuckle, and controlled internal and external torques (0.007 Nm/kg) were applied twice per condition. Joints were tested sequentially: intact, after pMCLX at the level of the planned TPLO osteotomy, following TPLO (target tibial plateau angle 5°), and after cranial cruciate ligament transection (CCLX). Internal rotation changed minimally after pMCLX (P = 1.0) but increased significantly following TPLO (P = 0.001) and CCLX (P = 0.002), with limited changes following CCLX (P = 1.0). External rotation increased significantly only between TPLO and CCLX (P = 0.02). These findings indicate that pMCLX does not contribute to significant rotational laxity, while TPLO increases internal rotation independently of CCL integrity. The stabilizing effects of quadriceps tension and axial loading highlight the importance of physiologic constructs in ex vivo models. Overall, these results challenge concerns about iatrogenic instability from pMCLX and support current TPLO positioning strategies.