Scanning electron microscopy of equine synovial membrane.

The scanning electron microscopy of synovial membrane from the radiocarpal and intercarpal joints near the lateral and medial borders of the tendon of the extensor carpi radialis muscle was studied in 5 ponies. Three different morphologic types of synovial membrane were observed. Type 1 synovial membrane was folded and had a surface mat of fibers separated by 1- to 5-micron-diameter holes. The 2nd and 3rd types of synovial membrane were both villous. The surface of type 2 synovial membrane was fibrillar but the surface of type 3 synovial membrane was cellular. The type of synovial membrane present was related to the function of the joint capsule region rather than to the type of subintimal connective tissue. Normal equine synovial membrane was found to be more villous in some regions of the joint capsule than synovial membrane of other species.