Chapter 9: Muscles and Muscle Tissue

Functionally, joints range from immovable synarthroses to slightly movable amphiarthroses to freely movable diarthroses. Synovial joints receive comprehensive coverage due to their complexity and frequency in the human body, with detailed analysis of their defining features including articular cartilage that reduces friction, the synovial cavity containing lubricating fluid, the articular capsule providing structural containment, and ligaments reinforcing stability. Six synovial joint types are distinguished by their structure and permitted motions: plane joints allowing gliding movements, hinge joints permitting flexion and extension along one axis, pivot joints enabling rotation, condylar joints facilitating movement in two planes, saddle joints offering similar biaxial motion, and ball-and-socket joints providing multiaxial movement. The chapter systematically explores joint movements including the primary actions of flexion, extension, abduction, adduction, and rotation, along with specialized movements such as pronation, supination, dorsiflexion, plantar flexion, inversion, and eversion. Detailed anatomical examination of major articulations including the temporomandibular, shoulder, elbow, hip, knee, and ankle joints describes their unique structural features, supporting ligaments, and functional capabilities. Joint stability emerges as a critical concept dependent on articular surface shape, ligament integrity, and surrounding muscle activation. The chapter concludes by addressing common joint pathologies including sprains, cartilage degeneration, dislocations, inflammatory conditions such as bursitis and tendonitis, and various forms of arthritis, providing clinical context for understanding joint dysfunction and degeneration.