What are the risk factors for Baker's cyst?

A Baker's cyst is a fluid-filled swelling behind the knee. It often develops when irritation inside the joint increases the amount of joint fluid. Knee osteoarthritis can inflame the joint lining and is a very common contributor. A meniscus tear may also cause irritation and extra fluid. Sports injuries, repeated kneeling, or another problem that keeps the knee swollen can have a similar effect.

Having a risk factor does not confirm that the swelling is a Baker's cyst. A clinician may examine the knee and use imaging when the diagnosis is uncertain or another cause needs to be excluded.

Notice whether the swelling changes with knee activity, bending, or rest, and record any locking, catching, or recent injury. Reduce activities that clearly aggravate pain while keeping gentle movement within comfort. Ice wrapped in a cloth may ease discomfort for a short period. Treatment usually focuses on the knee problem driving the fluid buildup, such as [Knee Osteoarthritis](/conditions/knee-osteoarthritis/) or a [Meniscus Tear](/conditions/meniscus-tear/). Do not puncture or massage a new lump without medical advice.

Arrange an assessment if a lump behind the knee persists, returns, limits bending, or appears after an injury. Seek urgent care for sudden calf swelling, warmth, redness, severe pain, or breathlessness, because a clot or a ruptured cyst can produce overlapping symptoms and needs prompt evaluation.

Could osteoarthritis, a meniscus problem, or another knee condition be causing the fluid? Do I need an examination or imaging? Which activities and exercises are suitable while the knee is swollen? What changes should make me seek urgent care?