In orthopaedics, the term "subluxation" implies the presence of an incomplete or partial dislocation of a joint. This will usually require medical attention to help relocate or reduce the joint. Joints that are prone to subluxations are the elbows, shoulders, fingers, knees, and hips affected by hip dysplasia. A spinal subluxation is relatively rare, but can sometimes impinge on spinal nerve roots, causing symptoms in the areas served by those roots. In the spine, such a displacement may be caused by a fracture, spondylolisthesis or severe osteoarthritis.