Lateral Stabilizing Structures of the Knee: Functional Anatomy and Injuries Assessed with MR Imaging

Abstract

The lateral aspect of the knee is stabilized by a complex arrangement of ligaments, tendons, and muscles. These structures can be demonstrated with routine spin-echo magnetic resonance (MR) imaging sequences performed in the sagittal, coronal, and axial planes. Anterolateral stabilization is provided by the capsule and iliotibial tract. Posterolateral stabilization is provided by the arcuate ligament complex, which comprises the lateral collateral ligament; biceps femoris tendon; popliteus muscle and tendon; popliteal meniscal and popliteal fibular ligaments; oblique popliteal, arcuate, and fabellofibular ligaments; and lateral gastrocnemius muscle. Injuries to lateral knee structures are less common than injuries to medial knee structures but may be more disabling. Most lateral compartment injuries are associated with damage to the cruciate ligaments and medial knee structures. Moreover, such injuries are frequently overlooked at clinical examination. Structures of the anterolateral quadrant are the most frequently injured; posterolateral instability is considerably less common. Practically all tears of the lateral collateral ligament are associated with damage to posterolateral knee structures. Most injuries of the popliteus muscle and tendon are associated with damage to other knee structures. MR imaging can demonstrate these injuries. Familiarity with the musculotendinous anatomy of the knee will facilitate accurate diagnosis with MR imaging.

Posterolateral and Posteromedial Corner Injuries of the Knee

“…2). Further cadaveric, 10 MRI [11][12][13][14][15][16][17][18] and ultrasound scan 7,19 evaluations of specific PLC anatomy followed Seebacher's original work to delineate the imaging counterpart of his anatomic description. Because of the increasing interest in the anatomy and biomechanics of the PLC corner of the knee in the orthopedic literature, the need for standardization and a systematic approach to the nomenclature of the lateral complex structures and PLC has been addressed.…”

“…Injuries of the PLC are less common than injuries of the PMC, but because this anatomic area is subject to a greater stress during motion than the medial side, they tend to be more disabling. 13 PLC injuries most commonly occur via a direct blow to the anteromedial aspect of the proximal tibia in the fully extended knee, with the force directed in a posterolateral direction, but can also occur from a hyperextension injury with external rotation. 41,44 Anterior rotatory dislocations (varus stress and hyperextension) and posterior rotatory dislocations (varus stress, posteriorly directed blow to proximal tibia and flexion), are also common mechanisms of injury, 20,45 the latter known as a "dashboard injury."…”

“…Complete tendon tears may present as an interruption of the muscle belly appearing as a masslike lesion with surrounding edema. 13 Enlargement of the muscle belly or disruption of muscle fibers may be apparent. Only 8% of all popliteus injuries occur in an isolated fashion, with isolated cases of muscle or tendon lesions reported in skiers, 55 football, [55][56][57] soccer, 58,59 rugby, 60 and polo players.…”

“…61 Lesions of the popliteus muscle are usually combined with injuries to other knee structures. 13 Brown and colleagues, 54 in their MRI analysis of popliteus injuries (n 5 24), reported combined injuries in 92% of cases, with involvement of its muscular portion in 96% of patients. Associated injuries included ACL (17%) or PCL (29%) tears, combined medial (46%) or lateral (25%) meniscal injuries, and medial (8%) or lateral (4%) collateral ligament lesions.…”

“…13,80 In their evaluation of avulsion fractures of the lateral femoral condyle in children, Sferopoulos and colleagues 81 reported 2 cases of avulsive fracture of the Gerdy's tubercle. Both of these were sport-related injuries from a direct blow to the medial aspect of the knee while playing football.…”