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What Is Causing Your Knee Pain? (Illustrated)


Updated July 01, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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Step 2 of 5 - Synovial Fluid (Normal Knee Joint)
Cut-section view of normal knee joint

Cut-section view of normal knee joint.

Photo © A.D.A.M.

A normal knee joint is surrounded by a membrane, the synovium, which produces a small amount of thick fluid (synovial fluid). The fluid helps to nourish the cartilage and keep it slippery. The synovium also has a tough outer layer (the joint capsule) which protects and supports the joint.

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