Heterotopic ossification (HO) takes place when something triggers basic cells in the muscle to start forming bone cells. This becomes calcified and forms a hard mass in the muscle. HO can be painful and limit motion, but over time, the problem can go away. The body slowly breaks down and absorbs the bone.
Rarely, surgery is done to remove the mass. If recognized early, radiation can be done. This prevents cells from making more cells. If your husband has a joint replacement in the future, radiation may be advised before the operation. This will help prevent the problem from occurring again.