6.pptx: Understanding Joint Stability: Factors and Mechanisms
- 1. Understanding Joint Stability: Factors and Mechanisms Dr.Ayesha (physiotherapist)
- 2. Introduction: Understanding Joint Stability: Factors and Mechanisms • Joint stability is crucial for maintaining proper function and preventing injuries. • It relies on three main factors: articular surfaces, ligaments, and muscle tone.
- 3. Articular Surfaces: • Morphology of bony articular surfaces contributes to joint stability. • Some joints have tight-fitting frameworks due to bone shapes (e.g., hip joint, ankle joint). • In other joints, bone shapes contribute little to stability (e.g., acromioclavicular, calcaneocuboid, knee joints).
- 4. Ligaments: • Fibrous ligaments prevent excessive joint movement but may stretch over time. • Elastic ligaments return to their original length after stretching. • Examples include ligaments supporting foot arches and auditory ossicles.
- 5. Muscle Tone: • Muscle tone is a major factor controlling joint stability. • Examples include muscles around the shoulder joint, knee joint, and foot arches. • Without proper muscle tone, joints become unstable and prone to dislocation or collapse.
- 6. Joint Nerve Supply: • Joint capsule and ligaments receive abundant sensory nerve supply. • Sensory nerves supplying joints also innervate muscles moving the joint and overlying skin (Hilton's law).
- 7. Types of Ligaments: • Fibrous ligaments are dense bundles of collagen fibers and are not stretchable under normal conditions. • Examples include iliofemoral ligament and collateral ligaments. • Elastic ligaments regain their original length after stretching due to elastic tissues. • Examples include ligamentum flavum and calcaneonavicular ligament.
- 8. Bursae and Synovial Sheaths: • Bursae are closed fibrous sacs lined with synovial membrane, reducing friction in areas subject to friction. • Synovial sheaths are tubular bursae surrounding tendons, reducing friction between tendons and surrounding structures. • Examples include prepatellar bursa and synovial sheaths around tendons passing under ligaments.