THE BICEPS FEMORIS MUSCLE COMPLEX AT THE KNEE - ITS ANATOMY AND INJURY PATTERNS ASSOCIATED WITH ACUTE ANTEROLATERAL-ANTEROMEDIAL ROTATORY INSTABILITY

We dissected 30 cadaveric knees to provide a detailed anatomic descrip tion of the biceps femoris muscle complex at the knee. The main compon ents of the long head of the muscle are a reflected arm, a direct arm, an anterior arm, and a lateral and an anterior aponeurosis, The main components of the short head of the biceps femoris muscle are a proxim al attachment to the long head's tendon, a capsular arm, a confluens o f the biceps and the capsuloosseous layer of the iliotibial tract, a d irect arm, an anterior arm, and a lateral aponeurosis. We examined 82 consecutive, acutely injured knees with clinical signs of anterolatera l-anteromedial rotatory instability for the incidence and anatomic loc ation of injuries to the biceps femoris muscle, Injuries to components of that muscle were identified in 59 (72%) of these knees; 29 knees ( 35.4%) had multiple components injured, There were 3 injuries to the l ong head of the biceps femoris muscle (all in the reflected arm) and 8 9 to the short head. A statistically significant correlation (P = 0.01 ) was found between increased anterior translation with the knee at 25 degrees of flexion as demonstrated by the Lachman test and injury to the biceps-capsuloosseous iliotibial tract confluens. Additionally, ad duction laxity at 30 degrees of flexion correlated with a Segond fract ure (P = 0.04), These data establish, in part, the relationship of the biceps femoris complex injury to anterior translation instability.