A synovial joint is structured to facilitate freedom of motion in one or more of the
three planes around the three axes of any given joint.
This graphic of a typical synovial joint is a schematic representation rather than an
actual synovial joint, but it contains the structural features common to all synovial joints.
Label 1 Bones
The synovial articulation is formed between two bones. These bones are parts of
the skeleton. They are levers of motion. To them are attached skeletal muscles, which
provide the forces for motion.
Label 2: Articular Cartilages
Covering a portion of each bone is an articular cartilage. The portions covered
are the ends that would otherwise be in contact during the motions of the joint. Each
articular cartilage has a relatively smooth surface and some ability to act as a shock
Label 3: Joint Capsule
The joint area is surrounded by a dense FCT capsule that encloses the joint
Label 4: Synovial Membrane, Fluid and Cavity
The inner surface of this fibrous capsule is lined with a synovial membrane. The
synovial membrane secretes a synovial fluid into the synovial cavity, or joint space. The
synovial fluid is a very good lubricant. Thus, it minimizes the frictional forces between
the moving bones.
Label 5: Ligaments
The bones of the synovial joint are held together by ligaments. Ligaments are
very dense FCT structures that keep the bones from being pulled apart. These
ligaments may occur as either discrete, individual structures or as thickenings of the
Label 6: Skeletal Muscles
The skeletal muscles cross the synovial joint from one bone to the other. They
are attached to the bones. The tonic (continuous) contraction of these skeletal muscles
holds the opposing surfaces of the bones tightly together. When properly stimulated,
these muscles contract and cause motion of the bones around the joint.