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How does the joint capsule attach to the bones around a synovial joint?

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Medical illustration of a human knee joint in a parasagittal section just lateral to the midline, labeling ligaments, cartilage, meniscus, patella, synovial structures, and surrounding muscles and fat pads. — joint The ligaments and cartilage in a knee joint.

The joint capsule, also known as the fibrous capsule, attaches to the bones surrounding a synovial joint by transitioning into the periosteum, the dense fibrous membrane that covers the surfaces of bones.12

While the periosteum typically covers the entire surface of a bone, it is absent where bones are capped with cartilage at the joints. In these areas, the fibrous joint capsule serves as the structural connection between the articulating bones. Within the joint, the inner layer of this capsule—the synovial membrane—passes from the fibrous capsule to the synovial periostea. This arrangement ensures the joint cavity remains completely closed, containing the synovial fluid necessary for lubrication and movement.2134