Malunion" is a clinical term used to indicate that a fracture has healed, but that it has healed in less than an optimal position. This can happen in almost any bone after fracture and occurs for several reasons.
Malunion may result in a bone being shorter than normal, twisted or rotated in a bad position, or bent. Many times all of these deformities are present in the same malunion.
Malunions can also occur in areas where a fracture has displaced the surface of the joint. When this happens, the cartilage in the joint is no longer smooth. This may cause pain, joint degeneration, "post-traumatic arthritis" or catching or "giving-way" episodes resulting from instability or incongruency of the joint.