Based on an extensive review of the literature and dissections of 17 fresh-frozen knee specimens, the authors divide the lateral fascia lata of the knee into two functional components: the iliopatellar band and the iliotibial tract. Aponeurotic, superficial, middle, deep, and capsulo-osseous layers contribute to these two functional components. The superficial layer of the iliotibial tract, combined with the deep, and capsulo-osseous layers, is hypothesized to function as an anterolateral ligament of the knee. The iliopatellar band provides stabilization of the patella against a medially directed force and is dynamically influenced by the vastus lateralis. The relationship of the iliotibial tract to extraarticular reconstructions of the knee with anterolateral rotatory instability is discussed.

A knowledge of the patterns of injury to the components of the iliotibial tract allows a clearer interpretation of motion limits testing in patients with abnormal anterior tibial translation of the knee (anterior cruciate ligament-deficient knees). Eighty-two consecutive patients with acute knee injuries were classified as anteromedial-anterolateral rotatory instability (anterior cruciate ligament-deficient) based on the abnormal motion demonstrated by clinical examination tests for instability. At surgery, injuries to the intraarticular and extraarticular anatomic structures were identified and correlated to the abnormal grades of motion demonstrated by the knee motion limits examination. Tears of the anterior cruciate ligament occurred in 80 (98%) of the knees. However, the grade of abnormal motion demonstrated by the Lachman and pivot shift tests was quite variable. This variation did not correlate statistically with anterior cruciate ligament tears. Injuries to the anatomic components of the iliotibial tract were confirmed in 76 (93%) of the knees. These injuries correlated highly with variations in grades of abnormal motion detected by the following tests: lateral joint line opening at 30 degrees (r2 = 0.05); Lachman test (r2 = 0.08); pivot shift (r2 = 0.16); and anterior translation at 90 degrees of flexion (r2 = 0.34). Thus, injuries to the components of the iliotibial tract are thought to contribute to the variation in grades of abnormal motion observed in this complex subgroup of anterior tibial translation instabilities.

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The functional anatomy of tha anterior cruciate ligament was studied in 18 freshly amputated specimens. The cruciates were observed in the extremes of flexion and extension, and in midposition in simulated weight-bearing and nonweight-bearing conditions. Five femoral shafts were split longitudinally so that the femoral and tibial attachments of the ligament could be inspected. The findings indicated that (1) the anterior cruciate ligament is a secondary static stabilizer against rotatory instabilities of the knee; (2) the anteromedial bundle contributes to anterolateral stability; (3) the intermediate bundle adds to straight and anteromedial stability; and (4) the posterolateral bundle assists in posterolateral stability. Specific bundles and functions of bundles must be considered in reconstruction, substitution, or replacement of the anterior cruciate ligament.