The popliteus muscle originates at the posteromedial aspect of the proximal tibial metaphysis and can have several attachments but primarily inserts on the lateral aspect of femoral condyle. The popliteus muscle functions as an internal rotator of the tibia on the femur and assists in flexion of the knee. It is an important stabilizer of the posterolateral corner of the knee and prevents forward translation of the femur on the tibia [117].

The overwhelming majority of injuries to the popliteus muscle occur at the muscle belly and myotendinous junction rather than the insertion, although this can occur [112]. The mechanism of injury is thought to be from a direct blow to the anteromedial aspect of the proximal tibia as the knee is hyperex-tended. Without contact, injury can occur with external rotation and hyperextension. Most injuries to the popliteus are found in conjunction with injuries to other structures in the knee, most commonly the ACL, with associated injuries to the PCL, menisci, or collateral ligaments also reported [117]. A small minority of popliteus injuries occurs in isolation [118,119].

Tears range from being partial interstitial to complete rupture. MRI will reveal enlargement of the muscle with increased signal on T2-weighted images (Fig. 27). With complete rupture, there will be retraction and clumping of the muscle and possible formation of a hematoma in the proximal calf [117]. In this situation, hematoma can compress the neurovascular bundle in the proximal calf, causing temporary compromise of the posterior tibial nerve [119]. More recently a case of popliteus strain with muscle edema and enlargement resulted in a permanent partial deficit of the tibial nerve [120].

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