Shape, size and arrangement of articular surfaces
The joints of the body come in all shapes and sizes. The most important factor to take into account here isrelativeof theof the two articular surfaces.
For example, in the shoulder joint, the humeral head of the upper arm is disproportionately larger thanglenoid fossaof the shoulder blade in which it sits – makes the joint more unstable because there is less contact between the bones.
In contrast, the acetabulum of the pelvis completely encloses the femoral head, making the hip joint much more stable. But while the hip is more stable, the shoulder has a greater range of motion. Each link has this tradeoff specific to its function.
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Fig 1 – Articulating surfaces of the shoulder joint. Note how the humeral head is disproportionately larger than the glenoid fossa of the scapula.
