Transient osteoporosis of the hip / Bone marrow edema syndrome
Acute hip pain and loss of bone density from an unknown causes. More common in women during pregnancy, but I have seen it in both young and middle aged men. It usually improves spontaneously but can cause avascular necrosis and pathological femoral neck fractures. Plain radiographs may show a decrease in bone density compared to the opposite side, but MRI is diagnostic with diffuse marrow edema and large joint effusion. Treatment is symptomatic until the condition improves, but oral bisphosphonates can decrease pain and improve bone density quickly. As the circulation is not affected, intra-osseous injection is not required.
MRI of the pelvis showing diffuse edema in the left proximal femur.