What Is a Synovial Membrane?

A synovial membrane is a layer of soft connective tissue that lines tendon sheaths, movable joints, and bursae, the fluid-filled sacs between tendons and bone, explains Arthritis-health.com and PubMed Health. Its function is the production of synovial fluid, which provides lubrication and also delivers nutrients to and removes waste from the cartilage inside a joint.

The synovial membrane is important for proper function and protection of joints and tendons. Synovial joints, such as ball-and-socket and hinge joints, allow for movement and are the most common type of joint, according to Arthritis-health.com. The synovial membrane encapsulates the surface of these joints as well as the tendons that attach bone to muscle and provides lubrication for these connections through the production of synovial fluid. A synovial membrane also lines small sacs of synovial fluid called bursae that provide additional lubrication and cushioning to further protect the joint.

Synovial membranes are extremely thin, notes Arthritis-health.com. They are often no wider than a human hair and consist of two layers. The outer layer, called the subsynovial membrane, is slightly thicker than the inner layer. Damage to the synovial membrane or associated support structures such as tendons and ligaments can lead to a variety of joint-related problems, including bursitis, tendinitis and various types of arthritis.