Need to stabilize joint to limit range of motion and reduce risk of injury. When muscle pulls on bone, is movement encouraged or opposed. Heavy capsule with intra and extracapsular ligaments Tendons and massive muscles. Elbow has interlocking articulating bones, with capsule, and ligament support Shoulder joint has only ligaments, muscles and tendons. Tear ligaments Distort capsule.
Point can move.
Shaft can change angle with surface. PLUS degree of angle. Like path of arm when drawing a big circle on board. No joint rotates freely, only partial rotation possible. Monaxial articulation allows movement along 1 axis only.