Transient osteoporosis is a self-limited condition characterised by reparative bone remodelling, which can affect all weight-bearing joints, being most common in the femoral head (see transient osteoporosis of the hip).
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Clinical presentation
Typical symptoms are pain with sudden onset in the affected joint, gait disturbance, and limited range of motion. Regional migratory osteoporosis is a specific form of the disorder, in which the transient osteoporosis migrates between joints 1,2.
Radiographic features
Plain radiograph
In only 20% of cases, osteopenia becomes visible after a delay of 4-8 weeks following symptom onset 1.
MRI
MRI is the modality of choice. Features include:
high T2/PDFS signal similar to bone marrow oedema without a necrotic core 1
subchondral fracture lines: found in up to 49% of cases 3
sparing sign (sparing of the medial bone marrow of the femoral head by bone marrow oedema): found in 88% of patients, disappears towards the later stages of the disease 3
Nuclear medicine
On bone scans the affected area shows increased radiotracer uptake (cf. osteonecrosis which demonstrates focal photopenia) 1.
Differential diagnosis
subchondral stress response
subchondral insufficiency fracture
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