Transient osteoporosis of the hip.

Transient osteoporosis of the hip (TOH) is an uncommon but possibly underdiagnosed condition. This pattern of regional osteoporosis affects previously healthy middle-aged men, and women in the third trimester of pregnancy. Its etiology is still unclear, yet in view of similarities to regional migratory osteoporosis and reflex sympathetic dystrophy, vascular and neurologic disturbances have been proposed as the possible pathogenetic mechanisms. Pain in the hip area and functional disability of the affected limb are the main clinical signs. Diagnosis is supported by local radiological osteopenia whose gradual disappearance parallels the spontaneous recovery. Bone scintigraphy, magnetic resonance imaging, computed tomography, and other imaging methods are supplementary diagnostic tools. Exclusion of more common entities is required. The purpose of this report is to elucidate the diagnostic and therapeutic aspects of TOH and to stimulate the physician's awareness of this condition, recognition of which may prevent unnecessary invasive procedures and inadequate treatment.