synovialleder

Synovialleder, or synovial joints, are the most movable joints in vertebrates. They are diarthroses, featuring a fluid-filled joint cavity that enables a wide range of movements while maintaining stability.

Anatomy: The articular surfaces of adjacent bones are covered with hyaline cartilage and interact within a joint capsule. The capsule consists of an outer fibrous layer and an inner synovial membrane that lines the joint and produces synovial fluid. The synovial cavity between the bones contains this fluid, which lubricates the joint and nourishes the cartilage. Ligaments provide passive stability, while muscles crossing the joint generate active movement. Many synovial joints also include structures such as menisci, articular discs, bursae, or tendon sheaths to improve fit, distribute loads, or reduce friction.

Function: The combination of cartilage, capsule, ligaments, and synovial fluid allows smooth, controlled motion, absorption and distribution of loads, and nourishment of joint tissues.

Types: Joints are classified by movement into plane, hinge, pivot, condylar, saddle, and ball-and-socket categories. Examples include the knee (primarily hinge with limited rotation), elbow (hinge), shoulder and hip (ball-and-socket), the wrist (condylar and plane components), and the temporomandibular joint (a modified hinge).

Development and pathology: Synovial joints form from mesenchymal tissue that cavitates to create the joint space, followed by development of the synovial membrane and capsule. Common pathologies include osteoarthritis (cartilage degeneration), rheumatoid arthritis (autoimmune synovitis), and inflammatory synovitis with joint effusion.