Pathomechanics of Post-traumatic Knee Injuries

Abstract

High and rapid impact activities are widely known to subject the knee joint to abnormal kinetics and kinematics that will increase injury risk. We hypothesize that impact loads applied to the knee joint to simulate an injurious landing task are able to induce anterior cruciate ligament injury; at the same time, these loads can also inflict significant cartilage damage which may accelerate the risk of developing early-onset osteoarthritis. Five cadaveric knees were mounted to a material testing system at 70-deg flexion. Rotational and translational joint motion during compression was registered using motion-capture system. Compression was successively repeated with higher actuator displacement until a significant decrease in load response was noted; ligament failure was determined by magnetic-resonance imaging and dissection. Pre- and post-test cartilage thickness at anterior, exterior, posterior and interior tibiofemoral regions were measured using magnetic-resonance scans. Osteochondral explants were subsequently extracted from these regions and histologically-assessed using modified Mankin scoring system. All specimens sustained anterior cruciate ligament failure; significant compressive force drop (80–91%) and substantial posterior femoral displacement (7.6–18.0mm) were observed. Significant reduction in cartilage thickness was found post-failure, especially for posterior-exterior tibiofemoral regions. Mankin scoring further confirmed considerable lesions at posterior regions. The cartilage damage profiles implied a ligament failure mechanism dominated by anterior tibial translation; this level of damage was analogous to mild-moderate osteoarthritic stages. Large impact loads can cause both anterior cruciate ligament injury and cartilage lesions, which may synergistically lead to early-onset osteoarthritis.