A synovial cyst adjacent and posterior to the knee joint is known as what?

• A. Baker cyst
• B. Ganglion cyst
• C. Popliteal aneurysm
• D. Meniscal cyst

Answer: (A)

A Baker cyst is a posterior knee synovial cyst that forms when excess joint fluid distends the gastrocnemius–semimembranosus bursa in the popliteal space, creating a fluid-filled sac behind the knee that communicates with the knee joint. This location—adjacent and posterior to the knee joint—and the origin from knee joint fluid are what define it. It commonly accompanies knee disorders that raise synovial fluid, such as arthritis or a meniscal tear, so the cyst sits in the popliteal fossa behind the knee and often reflects underlying joint pathology.

This differs from a ganglion cyst, which can occur near joints but is not characteristically a behind-the-knee popliteal structure. A popliteal aneurysm is a vascular dilation and would be pulsatile, possibly with a bruit. A meniscal cyst is associated with a meniscal tear and tends to lie along the joint line near the meniscus rather than in the popliteal fossa behind the knee.