Synovial Joints – Meaning, Classification, Types

Synovial Joint Types & Examples

 Differences between atypical, complex and compound synovial joints?

 

• If the articular surfaces of a synovial joint are covered by a fibrocartilage, it is termed atypical synovial joint, e.g. temporomandibular joint.
• If the cavity of a synovial joint is divided completely or incompletely into two compartments by an intra-articular disc, it is called complex synovial joint, e.g. temporomandibular joint and sternoclavicular joint.
• If more than two articular surfaces are enclosed in a single fibrous capsule, it is called a compound synovial joint, e.g. elbow joint.

 Classify various types of synovial joints

 

• Plane joints: These are the joints in which the articular surfaces are flat and in contact. Only gliding movements are possible at these joints. Examples: Intercarpal joints and intertarsal joints.
• Hinge joints: These are the joints in which one articular surface is convex and the other is reciprocally concave. The movements take place around a transverse axis. Examples: Humeroulnar joint, interphalangeal joints, knee joints and ankle joints.
• Pivot joints: These are joints in which a bony pivot-like process rotates within an osseofibrous ring or an osseofibrous ring rotates around the bony pivot. Thus, the movements are possible only around a longitudinal axis through the centre of the pivot. Examples: Superior radioulnar joint, inferior radioulnar joint and median atlantoaxial joint.
• Condylar joints: In such joints, the convex condyle or condyles (articular surfaces) of one bone articulate with concave articular surfaces or surfaces of other bone. Movements occur not only mainly in the transverse axis but also partly in the vertical axis (rotation). Examples: Knee joint and temporomandibular joint.
• Ellipsoid joints: These joints are formed by an oval convex surface of one bone and an elliptical concave surface of the other bone. Examples: Radiocarpal joint (wrist joint) and metacarpophalangeal joints. Movements that are possible at such joints are flexion, extension, abduction, adduction and circumduction. No rotation occurs around a central axis.
• Saddle joints: In such joints, the articular surfaces are reciprocally concavoconvex (saddle-shaped). Movements permitted at these joints are the same as in the condylar type with some rotational movement. Examples: Carpometacarpal joint of thumb, sternoclavicular joint, calcaneocuboid joint and incudomalleolar joint.
• Ball and socket joints: In such joints, the rounded articular surface of one bone (the ball) fits into a cup-shaped cavity (the socket) of the other bone. In these joints, the movements are possible in every direction around a common centre. Examples: Hip joint and shoulder joint.

Synovial Joint Types, Movements & Structure

A synovial joint is a joint with a cavity between two or more articulating bones. The cavity is lined by a synovial membrane and is filled with a synovial fluid. The synovial joints permit free movement, hence functionally classified as diarthrosis.

Typical Synovial Joint Characteristic features The characteristic features of a typical synovial joint:

• Articular surfaces are covered with hyaline (articular) cartilage, which provides a smooth, slippery surface to reduce friction between the articular surfaces of the bones during movement.
• Articular ends of bones are enclosed by a fibrous capsule; hence, it has a joint cavity.

Read And Learn More: Selective Anatomy Notes And Question And Answers

• The inner surface of the capsule and all intra-articular structures, except articular cartilages, are covered by a synovial membrane, which secretes synovial fluid.
• They are freely movable joints, hence functionally classified as diarthroses.
• The joint cavity is filled with synovial fluid.