Anatomy:
Inverted U shaped bursa along anterosuperior margin of semimembranosus (abutting medial meniscus)
Located between semimembmanoso-gastmocnemial bursa (superior) and pes anserinus bursa (inferior)
Proximal deep pocket (between semimembranosus and medial tibial condyle) and distal superficial pocket (between semimembranosus and MCL) form 2 arms of 'U' and both are joined superiorly (base of U)
Proximal end of bursa is located where semimembranosus crosses knee joint line posteromedially and distal end extends 1-2 cm below joint line
No communication with other bursae or knee joint
During extension, external rotation, valgus stress, semimembranosus tendon is scissored between MCL and medial tibial condyle and this bursa protects the tendon
References:
1. Rothstein CP et al.Semimembranosus-tibial collateral ligament bursitis: MR imaging findings. AJR Am J Roentgenol 1996; 166:875–877
