Popliteal cyst, an accumulation of synovial fluid, is common. It is usually the result of a knee joint abnormality such as arthritis or a cartilage tear.
May present with swelling or pain behind the knee, but most cases are asymptomatic.
May rupture, leading to severe pain and calf swelling.
Usually only conservative treatment is required.
Large symptomatic cysts that do not resolve may require drainage or sometimes surgical excision.
Popliteal cyst (also known as Baker's cyst) is the result of an accumulation of joint synovial fluid outside the knee joint; it forms behind the knee in the interval between the semimembranosus and the medial gastrocnemius. This occurs via increased intrasynovial pressure, and causes the synovial capsule to bulge at an area where there is a lack of external anatomical support. The most common underlying conditions that lead to overproduction of synovial fluid include arthritis and meniscal tears.
History and exam
Key diagnostic factors
- presence of risk factors
- popliteal bulge
- knee pain
- leg swelling
- calf tenderness
Other diagnostic factors
- calf ecchymosis
- lyme disease
- knee joint trauma
- underlying knee joint arthritis or synovitis
- underlying knee joint infection
- increasing age
1st investigations to order
- duplex ultrasound of the leg
Investigations to consider
- MRI of the leg
- CT scan of the leg
symptomatic: initial treatment
symptomatic: refractory to initial conservative treatment
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