The most mobile of all joints in the human body, the ball and socket joint consists of a rounded surface that articulates with a concave surface. The shoulder joint and the hip joint are large ball and socket joints.
Classification
A ball and socket joint is classified as a diarthrodial joint. Diarthrodial joints allow for freedom of movement, and are connected together with ligaments.
Anatomy
In a ball and socket joint, the bones are covered with cartilage and surrounded by a synovial membrane. Ligaments connect the bones together and muscle tendons provide additional support to the joint. The humerus, or arm bone, and the glenoid cavity of the scapula, or shoulder blade, comprise the shoulder joint. The hip joint consists of the head of the femur, or thigh bone, which fits into the acetabulum of the pelvis.
Function
The motion allowed at any joint is partly determined by its unique shape. The ball and socket joint allows for movement in all axes. Movements include flexion, extension, abduction, adduction and rotation.
Comparison of Two Ball And Socket Joints
While the shoulder joint is more mobile, the less flexible hip joint provides more stability. Ball and socket joints are designed to support weight and force. However, the shoulder joint relies on a delicate interplay of ligaments and tendons so it is more prone to injury.
Other Terms for Ball And Socket Joint
A ball and socket joint is also known as an enarthrodial joint or spheroidal joint.
References
- "Musculoskeletal assessment: joint range of motion and manual muscle strength";Hazel M. Clarkson; 1989
- Encyclopædia Britannica Online; "Ball and Socket Joint"; 2010
- Theodora.com: Humeral Articulation or Shoulder-joint
