Abstract
We investigated the biomechanical significance of bone bruises in patients with patella dislocation. Thirty-four patients with acute dislocation of the patella were studied. Redislocations were excluded. There were 11 men and 20 women with a mean age of 18 years at the time of injury. Bone bruises were noted at the periphery of the lateral femoral condyle in 22 patients (65%) and in 10 cases (29%) at the medial patellar facet. The sulcus angle in patients with bone bruises at the lateral femoral condyle was significantly greater and tibiofemoral rotation at the knee was significantly smaller than in patients without bone bruises. In knees with small tibiofemoral rotation, a large lateral displacement force applied into the knee joint is needed to displace the patella. The flat femoral trochlea groove, however, can not reduce the force, resulting in hard impaction between the medial patella facet and the lateral femoral condyle producing bone bruises.
