Transient osteoporosis of the hip

Last revised by Khalid Alhusseiny on 8 Mar 2023

Transient osteoporosis of the hip, also known as (transient) bone marrow edema syndrome of the hip, is a self-limiting clinical entity of unknown cause, although almost certainly a vascular basis and possible overactivity of the sympathetic system exists. It presents a synonym of the subchondral insufficiency fractures of the knee

Although initially described in pregnancy, transient osteoporosis of the hip tends to affect middle-aged men (40-55-year-olds) with an M:F ratio of 3:1. When women are affected, it is usually during the 3rd trimester of pregnancy. Generally, only one hip is affected at a time. Recurrence in the same hip is possible.

Typically, patients present with spontaneous onset of hip pain, usually progressive over several weeks. Patients generally do not have risk factors for avascular necrosis and do not go on to form avascular necrosis.

In some instances, patients can go on to develop similar changes in the opposite hip or in other joints; such cases should be referred to as regional migratory osteoporosis.

Typically plain radiographs are normal initially but usually become abnormal by 4-8 weeks following the onset of symptoms. Findings include:

  • subchondral cortical loss involving femoral head and neck: virtually pathognomonic; present in only 20% of cases after 4-8 weeks from symptom onset 2
  • often profound osteopenia of the femoral head and neck region
  • joint effusion may be present 
  • joint space always preserved

MRI is the modality of choice for the detection of transient osteoporosis of the hip and demonstrates bone marrow edema pattern involving the femoral head, neck, and even intertrochanteric region without findings of osteonecrosis 5. Subchondral fracture lines can be found in almost half of cases 6. Sparing of the medial femoral head by bone marrow edema can be found in almost 90% of patients and disappears towards the later stages of the disease 6.

  • T1: decreased signal with loss of normal fatty marrow signal
    • it is worth having a coronal of both hips so that one can compare the distribution of red marrow
  • T2: high signal, often heterogeneous, may be striking

Typically, bone scintigraphy demonstrates markedly increased homogeneous uptake in the femoral head; a finding which is seen well before osteopenia is seen on plain films. Bone scintigraphy is not the modality of choice for the evaluation of these patients. 

Typically transient osteoporosis of the hip resolves spontaneously within 6-8 months after protected weight-bearing and pain control. In approximately one-fifth, edema will recur in the same or another site of the skeleton, in which case the condition is called regional migratory osteoporosis 6.

General imaging differential considerations include:

  • early avascular necrosis: avascular necrosis at early stages does not present with bone marrow edema
  • late avascular necrosis
    • absence of subchondral low signal on T2 or contrast-enhanced T1 images suggests a favorable outcome, i.e. reversible disease
    • dynamic contrast-enhanced MRI will show hyperemia (early enhancement) in transient osteoporosis vs no enhancement in early avascular necrosis
    • no sufficient evidence exists for the use of dynamic contrast-enhanced (DCE) MRI to distinguish between the two conditions
  • stress fracture / subchondral stress response 5
  • septic arthritis
  • reflex sympathetic dystrophy: more commonly involves upper extremities; vasomotor dysfunction and skin changes more often seen; more debilitating
  • tuberculous arthropathy of the hip

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Cases and figures

  •  Case 1
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  • Case 2
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  • Case 3
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  • Case 4: bilateral
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  • Case 5
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  • Case 6: with subcapital fracture
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  • Case 7
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