Melorheostosis.

Melorheostosis is a seemingly rare condition of unknown etiology. Although it affects bone primarily, it may also involve soft tissue. The lower extremities are most frequently affected, and joints may become stiff as a result of obstruction of joint motion by thickened cortical sclerosis. The disease is difficult to diagnose in the early stages before bone changes become evident, and it is easily misdiagnosed. Surgery may be required to prevent deformity or to restore normal function.