I. Normal Joint Structures and their Reaction to Injury

The framework of the human body is essentially composed of a series of bones that articulate at joints and are moved by muscles. The joints form an integral part of this complex system since they allow motion to take place and/or hold parts of the bony skeleton together. Although there are several different kinds of joints, since the synovial joint is encountered most often, this article will be limited to discussing this type of articulation. The synovial joint is constructed to allow movement in one or more directions between two or more major segments of the human skeleton under weight-bearing and/or nonweightbearing conditions. The joint provides a low friction articulation to enable movement of the body with minimal effort. The essential components of a synovial joint are: the synovial membrane, synovial fluid, articular cartilage, the joint capsule, and in some cases, intraarticular structures (such as menisci in the knee joint). The normal structure and function of each of these components and the response of these tissues to injury will be presented in this first of 3 articles. J Orthop Sports Phys Ther 1979;1(1):16-22. doi:10.2519/jospt.1979.1.1.16