The joint capsule, also known as the articular capsule, is a fibrous membranous structure that surrounds a joint, connecting the bones that form it and enclosing the joint cavity. It consists of two layers: the outer fibrous layer, which provides mechanical strength and stability to the joint, and the inner layer, the synovial membrane, which produces synovial fluid essential for lubrication and nourishment of the articular surfaces.
The joint capsule plays a crucial role in maintaining joint stability by limiting excessive or abnormal movements. At the same time, it has a rich nerve supply with proprioceptive receptors that provide information to the central nervous system regarding the position and movement of the joint.
Pathological conditions affecting the joint capsule include inflammation of the capsule (capsulitis), which may cause pain and stiffness, as well as chronic fibrosis and contraction, as characteristically occurs in frozen shoulder (adhesive capsulitis), leading to significant restriction of the joint’s range of motion.
The integrity of the joint capsule is particularly important in cases of traumatic dislocation, as rupture or laxity of the capsule may result in chronic joint instability.