Bone marrow edema and associated pain in early stage osteonecrosis of the femoral head: Prospective study with serial MR images

PURPOSE: To determine whether the marrow edema around focal osteonecrosis o n magnetic resonance(MR) images is associated with clinical symptoms. MATERIALS AND METHODS: Thirty-three patients with 37 hips showing early sta ge osteonecrosis of the femoral head were followed up at 3-month intervals with clinical evaluation, conventional radiography, and serial MR imaging. RESULTS: Seven (50%) of 14 symptomatic hips showed marrow edema around foca l osteonecrosis on initial MR images, whereas only one (4%) of 23 asymptoma tic hips showed edema (P<.01). Six (86%) of seven hips that were moderately to severely painful were associated with surrounding marrow edema. Ail eig ht hips showing osteonecrosis with marrow edema at the initial MR examinati on had joint effusion and exhibited intense radionuclide uptake in the prox imal femur, which corresponded to the extent of edema on MR images. In all eight hips, the marrow edema resolved on follow-up MR images, and the pain subsided with the resolution of edema. CONCLUSION: The results of this study suggest that the combination of marro w edema of the proximal femur and focal osteonecrosis of the femoral head a re strongly associated with hip pain in early stage osteonecrosis, even pri or to collapse. Pain improvement usually parallels the resolution of edema.