[1] Rarely complications such as deep vein thrombosis, peripheral neuropathy, ischemia, or compartment syndrome may occur.

[2][3] Risk factors include other knee problems such as osteoarthritis, meniscal tears, or rheumatoid arthritis.

[1][3][4] The underlying mechanism involves the flow of synovial fluid from the knee joint to the gastrocnemio-semimembranosus bursa, resulting in its expansion.

[1] Rupture of a Baker's cyst may also cause bruising below the medial malleolus of the ankle (Crescent sign).

Baker's cysts arise between the tendons of the medial head of the gastrocnemius and the semimembranosus muscles.

Diagnosis is confirmed by ultrasonography, although if needed and there is no suspicion of a popliteal artery aneurysm then aspiration of synovial fluid from the cyst may be undertaken with care.

An infrequent but potentially life-threatening complication, which may need to be excluded by blood tests and ultrasonography, is a deep vein thrombosis (DVT).

A burst cyst commonly causes calf pain, swelling and redness that may mimic thrombophlebitis.

Avoiding activities such as squatting, kneeling, heavy lifting, climbing, and even running can help prevent pain.