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Synovial joints are the most mobile joints of the skeleton. Each contains a cavity filled with lubricating fluid that allows the articulating bones to glide smoothly against one another. A strong fibrous capsule surrounds the joint, lined internally by a synovial membrane, while the bone surfaces are covered by a layer of smooth articular cartilage.
Key Features
- Joint cavity: Space filled with synovial fluid that reduces friction.
- Articular cartilage: Hyaline cartilage protecting the bone ends.
- Joint capsule: Fibrous outer layer with an inner synovial membrane.
- Ligaments: Reinforce and stabilize the joint capsule.
- Wide range of motion: Movement depends on the specific joint type.
Common Types
- Hinge – e.g., elbow and knee
- Pivot – e.g., radioulnar joint
- Condyloid – e.g., wrist (radiocarpal joint)
- Saddle – e.g., thumb (first carpometacarpal)
- Plane – e.g., intercarpal joints
- Ball-and-socket – e.g., shoulder and hip
Synovial joints enable most everyday motions, from walking and gripping to swinging a bat. Their design balances mobility with stability through supportive ligaments and surrounding muscles.