What surrounds synovial joints?

Synovial joints are unique in their structure and are characterized by the presence of a joint capsule, which surrounds and encloses the joint space. This joint capsule is composed of two layers: an outer fibrous layer that provides stability and support, and an inner synovial membrane that lines the joint cavity and produces synovial fluid. This fluid lubricates the joint, allowing for smooth movement and reducing friction between the articulating surfaces.

The presence of this joint capsule is crucial for the function of synovial joints, as it provides both mechanical support and helps maintain optimal conditions within the joint environment. The capsule also helps contain the synovial fluid, which nourishes and protects the cartilage that covers the ends of the bones within the joint, facilitating movement.

The other options stand to play important roles in the musculoskeletal system but do not directly surround synovial joints in the same way that joint capsules do. Ligaments provide stability to joints by connecting bones, cartilage cushions the ends of bones to reduce friction, and tendons attach muscles to bones, enabling movement. However, none of these structures form the enclosing layer like the joint capsule does.