Classification of Joints on the Basis of Function Synovial joints are the only joints that have a space or âsynovial cavityâ in the joint. Knees, elbows, and shoulders are examples of synovial joints. Synovial joints are capable of the greatest movement of the three structural joint types however, the more mobile a joint, the weaker the joint. Articular capsules may also possess ligaments that hold the bones together. The ends of the bones are covered with articular cartilage, a hyaline cartilage, and the entire joint is surrounded by an articular capsule composed of connective tissue that allows movement of the joint while resisting dislocation. Synovial fluid lubricates the joint, reducing friction between the bones and allowing for greater movement. This space is referred to as the synovial (or joint) cavity and is filled with synovial fluid. Synovial joints are the only joints that have a space between the adjoining bones ( Figure). Either type of cartilaginous joint allows for very little movement. Symphyses are found at the joints between vertebrae. In symphyses, hyaline cartilage covers the end of the bone but the connection between bones occurs through fibrocartilage. Synchondroses are found in the epiphyseal plates of growing bones in children. In a synchondrosis, the bones are joined by hyaline cartilage. There are two types of cartilaginous joints: synchondroses and symphyses. (credit: modification of work by Gray's Anatomy) Cartilaginous JointsĬartilaginous joints are joints in which the bones are connected by cartilage. Gomphoses are fibrous joints between the teeth and their sockets. The tooth is connected to the socket by a connective tissue referred to as the periodontal ligament. Gomphoses occur between teeth and their sockets the term refers to the way the tooth fits into the socket like a peg ( Figure). The amount of movement in these types of joints is determined by the length of the connective tissue fibers. An example of a syndesmosis is the joint of the tibia and fibula in the ankle. Syndesmoses are joints in which the bones are connected by a band of connective tissue, allowing for more movement than in a suture. Sutures are fibrous joints found only in the skull. Sutures are found only in the skull and possess short fibers of connective tissue that hold the skull bones tightly in place ( Figure). There are three types of fibrous joints: sutures, syndesmoses, and gomphoses. There is no cavity, or space, present between the bones and so most fibrous joints do not move at all, or are only capable of minor movements. The bones of fibrous joints are held together by fibrous connective tissue. The structural classification divides joints into bony, fibrous, cartilaginous, and synovial joints depending on the material composing the joint and the presence or absence of a cavity in the joint. There are two ways to classify joints: on the basis of their structure or on the basis of their function.

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