[1] Each joint capsule has two parts: an outer fibrous layer or membrane, and an inner synovial layer or membrane.

Each capsule consists of two layers or membranes: On the inside of the capsule, articular cartilage covers the end surfaces of the bones that articulate within that joint.

The outer layer is highly innervated by the same nerves which perforate through the adjacent muscles associated with the joint.

The fibrous membrane of the joint capsule is attached to the whole circumference of the articular end of each bone entering into the joint, and thus entirely surrounds the articulation.

This article incorporates text in the public domain from page 282 of the 20th edition of Gray's Anatomy (1918)