Subpopliteal recess

The subpopliteal recess (SPR) is a synovial recess that extends distally along the popliteus tendon in the posterolateral region of the knee. It was previously known as the "popliteus bursa", but this structure is an expansion of the articular cavity of the knee joint and note and not an isolate synovial bursa.

The subpopliteal recess is situated between the lateral tibial condyle and the popliteus muscle, and may extends distally 1 cm below the joint line. Its anteromedially bounded by the posterior horn of the lateral meniscus and its posterolaterally bounded by the the popliteus tendon.

Its length can vary, typically measuring around 22.64 ± 11.38 mm from the upper end of the lateral tibial condyle to the lower end of the depression.[1]

The SPR's morphology can be influenced by the presence of the fabellofibular ligament, which can make the recess significantly longer. The relationship between the popliteus muscle and the SPR can be classified into three types, with types 2 and 3 extending to the proximal tibiofibular joint, potentially causing knee joint instability.[1]