Description: Learn about the key factors influencing joint stability: articular surfaces, ligaments, and muscle tone. Understand how joint morphology, ligament integrity, and muscle strength contribute to preventing injuries and maintaining proper function.

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.