Joints where two bones articulate (come together) to allow a variety of motions where the union of the bony elements are surrounded by an articular capsule enclosing a cavity lined by a synovial membrane.

These joints include "ball and socket joints"; such as, the hips and shoulders that permit a wide range of movements in several directions; and the "hinge joints"; such as, the knees and elbows which allow movements primarily in one direction or plane.

Synovial joints consist of several components which make complex movements possible

• Synovial capsule, the outermost layer of strong fibrous tissue which resembles a sleeve as it surrounds the joint.
• Synovial membrane which lines the capsule and secretes synovial fluid.
• Synovial fluid, which flows within the synovial cavity, acts as a lubricant to make the smooth movement of the joint possible.
• Ligaments, bands of fibrous tissue that form joints by connecting one bone to another bone, or joining a bone to cartilage and complex hinge joints; such as, the knee, are made up of a series of ligaments which permit movements in different directions.
• Bursa (s), bursae (pl), a fibrous sac which acts as a cushion to ease movement in areas that are subject to friction; such as, in the shoulder, elbow, and knee joints; where a tendon passes over a bone.