Synovial joint

Synovial joints (or diarthroses, or diarthroidal joints) are the most common and most moveable type of joints in the human body. As with most other joints, synovial joints achieve movement at the point of contact of the articulating bones. Structural and functional differences distinguish synovial joints from cartilagenous joints (synchondroses and symphyses) and fibrous joints (sutures, gomphoses, and syndesmoses). The main structural differences between synovial and fibrous joints is the existence of a capsule surrounding the articulating surfaces of a synovial joint and the presence of lubricating synovial fluid within that capsule.

Common Features

 * 1) synovial capsule (a collagenous structure which encloses, supports and protects the joint. It often incorporates ligaments into its walls)
 * 2) synovial membrane (forms the inner lining of capsule, secretes synovial fluid)
 * 3) articular cartilage (hyaline cartilage padding on the articulating surfaces of joined bones)
 * 4) synovial fluid (a lubricating, nourishing fluid rich in mucopolysaccharide contained within the capsule)

Types

 * 1) Ball and socket joints, such as shoulder and hip joints. These allow a wide range of movement.
 * 2) Condyloid joints (or ellipsoidal joints), such as the wrist. A condyloid joint is where two bones fit together with an odd shape (e.g. an ellipse), and one bone is concave, the other convex. Some classifications make a distinction between condyloid and ellipsoid joints.
 * 3) Saddle joints, such as at the thumb (between the metacarpal and carpal). Saddle joints, which resemble a saddle, permit the same movements as the condyloid joints.
 * 4) Hinge joints, such as the elbow (between the humerus and the ulna). These joints act like a door hinge, allowing flexion and extension in just one plane.
 * 5) Pivot joints, such as the elbow (between the radius and the ulna). This is where one bone rotates about another.
 * 6) Gliding joints (or planar joints), such as in the carpals of the wrist. These joints allow a wide variety of movement, but not much distance