Medial Gastrocnemius Bursa

bursa musculi gastrocnemii medialis

The medial gastrocnemius bursa lies between the medial head of gastrocnemius and the posterior medial femoral condyle. In approximately 50% of adults it communicates with the knee joint through a natural fenestration, allowing synovial fluid from the joint to fill the bursa. When the semimembranosus bursa (adjacent to the medial gastrocnemius insertion) also communicates, a Baker cyst is formed from this combined three-way communication.

Region: Knee

Clinical Relevance

Clinical Notes

The medial gastrocnemius bursa is the primary anatomical basis of Baker cysts (popliteal cysts) together with the semimembranosus bursa. Increased intraarticular pressure from knee effusion (caused by meniscal tears, osteoarthritis, inflammatory arthritis, or ligamentous injury) forces fluid into the bursa through the natural communication, producing a posterior knee mass. Ultrasound confirms the cyst's connection to the joint. Treatment of the underlying intraarticular pathology is the primary management; direct cyst aspiration has a high recurrence rate.

Pathology

Common Injuries & Conditions

Baker Cyst Formation via Medial Gastrocnemius Bursa Communication

Persistent knee effusion from meniscal tear or inflammatory arthritis forces synovial fluid through the natural communication between the joint and medial gastrocnemius-semimembranosus bursal complex, forming a Baker cyst in the posteromedial knee; ultrasound confirms communication with the joint and treatment targets the underlying cause rather than direct cyst aspiration.