Dislocations and subluxations
In a dislocation, joint bones are displaced so that their articulating surfaces totally lose contact. Subluxations partially displace the articulating surfaces.
Dislocations and subluxations occur at the joints of the shoulders, elbows, wrists, digits, hips, knees, ankles, and feet; the injury may accompany fractures of these joints or result in deposition of fracture fragments between joint surfaces. Prompt reduction can limit the resulting damage to soft tissue, nerves, and blood vessels.
A dislocation or subluxation may be congenital (as in congenital dislocation of the hip), or it may follow trauma or disease of surrounding joint tissues (for example, Paget’s disease). Gender also has an influence on injuries, especially of the knee (See Dislocations and subluxations in men and women, page 274.)
Signs and symptoms
Dislocations and subluxations produce deformity around the joint, change the length of the involved extremity, impair joint mobility, and cause point tenderness.
When the injury results from trauma, it’s extremely painful and commonly accompanies joint surface fractures. Even in the absence of concomitant fracture, the displaced bone may damage surrounding muscles, ligaments, nerves, and blood vessels and may cause bone necrosis, especially if reduction is delayed.