Figure 1. Magnetic resonance imaging scans of three patients with lesions of osteonecrosis (arrows).

Shown are screening coronal T1-weighted images (left) and corresponding fat-suppressed T2-weighted images (right). A. Unilateral osteonecrosis in one patient. B and C. Bilateral osteonecrosis in two patients. In addition to having the curvilinear lesions of osteonecrosis, the patient at bottom (panel C) has increased signal in the head and neck of the left femur, consistent with edema surrounding the area of osteonecrosis. The patients in panels B and C developed symptoms after study enrollment.