Musculoskeletal Imaging

Membrane, synovial

the delicate, thin inner layer of the articular capsule that lines the nonarticular portion of synovial joints and any intra-articular ligaments or tendons. Most commonly it consists of two layers, a thin cellular surface layer or intima and a deeper vascular underlying layer or subintima. The synovial membrane also covers the intracapsular bone surfaces that are clothed by periosteum or perichondrium but are without cartilaginous surfaces ("marginal" or "bare" areas of the joint). Small finger-like projections termed synovial villi (see villus synovial) may occur on its inner surface. Among the functions of the membrane are secretion of synovial fluid, facilitation of and accommodation to the changing shape of the articular cavity that is required for normal joint motion, and assistance in the removal of substances from the articular cavity.

The synovial membrane of the knee is particularly complex, consisting of the following subparts:

  • the central portion;

  • a suprapatellar synovial pouch;

  • the posterior femoral recesses; and

  • the subpopliteal recess.

    In rheumatoid arthritis, the earliest pathologic abnormalities to be recognized are synovial proliferation associated with inflammation of the membrane (synovitis), capsular distension, and congestion and oedema of the synovial membrane.

    The synovial membrane is also involved in crystal deposition diseases. In calcium pyrophosphate dihydrate crystal deposition disease, crystals may be deposited in the membrane or migrate there, and calcification of the synovium is common. The joints affected most frequently are the wrist, knee, and metacarpophalangeal and metatarsophalangeal joints.

    Increased deposition of iron (haemosiderin) occurs in the synovial membrane in haemochromatosis, rheumatoid arthritis, degenerative disease, pigmented villonodular synovitis, haemophilia and haemarthrosis.

    In osteoarthritis synovial membrane changes may develop in severe cases, at times resembling the findings in rheumatoid arthritis.

    DR