Joint space narrowing is therefore a component of several radiographic classifications of osteoarthritis. For the temporomandibular joint, a joint space of between 1.5 and 4В mm is regarded as normal. The normal joint space is at least 2В mm in the hip (at the superior acetabulum), at least 3В mm in the knee, and 4вЂ“5В mm in the shoulder joint. A joint space narrowing is a sign of either (or both) osteoarthritis and inflammatory degeneration. The joint space equals the distance between the involved bones of the joint. rotation: a circular movement around a fixed point.extension: straightening limbs at a joint.adduction: movement toward the mid-line of the body.abduction: movement away from the mid-line of the body.The movements possible with synovial joints are: These allow for all movements except glidingД¬ondylar joint (condyles of femur join with condyles of tibia) and saddle joint (lower end of femur joins with patella) Saddle joints, where the two surfaces are reciprocally concave/convex in shape, which resemble a saddle, permit the same movements as the condyloid joints but allows greater movement. Some classifications make a distinction between condyloid and ellipsoid joints these joints allow flexion, extension, abduction, and adduction movements (circumduction).Д¬arpometacarpal or trapeziometacarpal joint of thumb (between the metacarpal and carpal - trapezium), sternoclavicular joint These joints act as a door hinge does, allowing flexion and extension in just one planeДЄtlanto-axial joint, proximal radioulnar joint, and distal radioulnar jointДЄ condyloid joint is a modified ball and socket joint that allows primary movement within two perpendicular axes, passive or secondary movement may occur on a third axes. These joints allow only gliding or sliding movements, are multi-axial such as the articulation between vertebrae. In ascending order of mobility, they are:Д¬arpals of the wrist, acromioclavicular joint

Others have multiple degrees of freedom, but at the expense of greater risk of injury. Some are relatively immobile, but are more stable. There are seven types of synovial joints. The blood supply of a synovial joint is derived from the arteries sharing in the anastomosis around the joint. A damage to this occurs in a Gosselin fracture.

The bone surrounding the joint on the proximal side is sometimes called the plafond, especially in the talocrural joint. Bursae - saclike structures that are situated strategically to alleviate friction in some joints (shoulder and knee) that are filled with fluid that is similar to synovial fluid.Accessory ligaments (extracapsular and intracapsular) - the fibers of some fibrous membranes are arranged in parallel bundles of dense regular connective tissue that are highly adapted for resisting strains to prevent extreme movements that may damage the articulation.Tendons - cords of dense regular connective tissue composed of parallel bundles of collagen fibers.Articular fat pads - adipose tissue pads that protect the articular cartilage, as seen in the infrapatellar fat pad in the knee.Articular discs or menisci - the fibrocartilage pads between opposing surfaces in a joint.Many, but not all, synovial joints also contain additional structures: Articular cartilage: the bones of a synovial joint are covered by this layer of hyaline cartilage that lines the epiphyses of joint end of bone with a smooth, slippery surface that does not bind them together articular cartilage functions to absorb shock and reduce friction during movement.Joint capsule: the fibrous capsule, continuous with the periosteum of articulating bones, surrounds the diarthrosis and unites the articulating bones the joint capsule consists of two layers - (1) the outer fibrous membrane that may contain ligaments and (2) the inner synovial membrane that secretes the lubricating, shock absorbing, and joint-nourishing synovial fluid the joint capsule is highly innervated, but without blood and lymph vessels, and receives nutrition from the surrounding blood supply via either diffusion (a slow process) or by convection, a far more efficient process achieved through exercise.Synovial cavity: all diarthroses have the characteristic space between the bones that is filled with synovial fluid.Synovial joints contain the following structures:

Movable joint