A patient in the third trimester of pregnancy started complaining of difficulty walking due to severe left hip pain radiating to the thigh. She reported progressive worsening of symptoms and persistence of pain after childbirth. There was no history of trauma, fever, steroid usage or complaints related to other joints.
A plain film of the pelvis was unremarkable.
MRI of the pelvis demonstrated diffuse bone marrow oedema at the head and neck of the left femur with low signal intensity on T1 weighted-images (WI) and high signal intensity on fat-suppressed T2WI. There were no signs of avascular necrosis or fractures. Minimal joint effusion of the left hip was also present.
A 3 months follow-up MRI showed complete resolution of the oedema and normal bone marrow signal. The contour of the femoral head was preserved.
Idiopathic transient osteoporosis of the hip (ITOH) is an uncommon disorder first described in pregnancy [1, 2, 8]. The aetiology remains unknown, even though various causes such as vascular disorders, trauma or sympathetic overactivity have been proposed [3, 4, 5, 6, 8].
ITOH is a rare cause of hip pain that most commonly occurs in middle-aged men (40-60 years-old) [6, 8, 10].
The typical clinical presentation is acute onset of pain in and around the hip joint that increases in weight-bearing positions [3]. Unilateral involvement is more common [1].
This condition has a self-limited course and spontaneous resolution in 6-12 months is the rule [1, 3, 5, 6, 8]. Management is conservative and essentially encompasses symptomatic relief and reduced weight bearing to prevent stress fractures [1, 5, 6, 7, 9]. Recurrence is possible in the same or in a different joint.
Radiographs are initially normal. Osteopenia and subchondral bone loss at the femoral head and neck may be evident later on (usually 4-8 weeks after the onset of symptoms) [3].
MR imaging is the most reliable method to the early diagnosis of ITOH [1, 3], showing areas of bone marrow oedema with low T1 and high T2 signal intensity affecting the femoral head, neck and also the intertrochanteric region [8, 9, 10]. Joint effusion commonly accompanies this disorder. These findings disappear after the clinical symptoms subside. Resolution of the condition is usually documented with a follow-up MRI [3, 5, 6, 8].
Awareness of this diagnosis as a cause of hip pain and its characteristic imaging appearance are important to prevent unnecessary intervention [1, 5, 6, 7, 9].
Idiopathic transient osteoporosis of the hip
Based on the provided anteroposterior X-ray of the pelvis and MRI images, the following features are observed:
• In early X-ray examinations, there is no obvious morphological abnormality of the left femoral head and neck, or only slight decrease in bone density. Significant osteoporosis may appear a few weeks after the onset of symptoms.
• MRI shows abnormal bone marrow signals in the region of the left femoral head and neck: low signal on T1-weighted images and high signal on T2-weighted images and fat-suppression sequences, with evident bone marrow edema.
• There may be a small amount of effusion within the joint capsule. The articular surface of the femoral head remains intact, with no obvious collapse or cystic changes.
• Compared with the contralateral side, no significant soft tissue mass or other occupying lesion is seen around the left hip.
Considering the patient is in the late stage of pregnancy (third trimester), has severe hip pain, and MRI suggests bone marrow edema while early X-ray findings are not prominent, combined with the absence of trauma, no long-term glucocorticoid use, and no significant infection or fever, the following diagnoses or differentials are considered:
Considering the patient’s pregnancy status, typical location of hip pain, clinical course (pain progressively worsening, not fully relieved postpartum), MRI evidence of bone marrow edema, and the lack of other risk factors or etiological support, the most likely diagnosis is Idiopathic Transient Osteoporosis of the Hip (ITOH). This condition is usually self-limiting and may resolve spontaneously within 6-12 months, but close follow-up and symptomatic management are required.
Treatment Strategy:
• Conservative Management: Primarily limiting weight-bearing on the affected side, using crutches or assistive devices to reduce hip joint stress, and using analgesics (e.g., NSAIDs) to control pain.
• Medications: Some patients may consider calcium and vitamin D supplementation and, under medical supervision and depending on bone density, bisphosphonates may be chosen.
• Surgical Indications: Surgery is typically unnecessary; it is only considered in rare cases of secondary structural damage/collapse of the femoral head or suspicion of other pathologies.
Rehabilitation/Exercise Prescription Suggestions (FITT-VP Principle):
1. Early Stage (Acute Pain Phase):
Disclaimer: This report is only a reference analysis based on the available imaging and clinical information, and cannot replace in-person consultation or professional medical advice. If you have any doubts or if symptoms worsen, please seek medical attention promptly.
Idiopathic transient osteoporosis of the hip
