1. Osteonecrosis

2.  A progressive deterioration of the femoral head or any other bone that is not receiving adequate vascular nutrition.

3. Causes  The exact etiology is not known. The level of unbound maternal cortisol gradually raises towards the end of pregnancy to a level about three times that in normal non-pregnant women. It has been speculated that the rise in unbound cortisol, estrogen and progesterone in late pregnancy, the increased interosseous pressure and a direct injury to the femoral joint by the compression of the growing uterus or during a difficult delivery may all act together to produce insufficiency of blood supply to the femoral head. Most of the cases are idiopathic.

4. Other Causes  Renal transplantation  Alcoholism  Autoimmune disorders (systemic lupus erythematosus, rheumatoid arthritis, polyarteritis nodosa)  Gout  Cushing’s disease  Pancreatitis  Polycythaemia  Cryoglobulinaemia  Decompression sickness  Sickle-cell anaemia  Liver disease  Infections

5. Signs and Symptoms  During the last trimester or at delivery (in relatively older mothers)  Higher rate of involvement of the left hip  Increasing pain of variable severity  Usually unilateral  Deep pain in the groin  Pain radiates to the knee, thigh, or back  Pain exaggerated by standing and walking  Painful limitation of AROM or PROM of the hip joint  Positive Trendelenburg gait on the affected side

6. PT Implications  MRI should distinguish between osteonecrosis and TPO. Decrease weight bearing, osteotomy, use of a non- vascularized structural graft, electrical stimulation, core decompression and use of a vascularised structural graft.

7. References  Goodman, Catherine Cavallaro and Snyder, Teresa E. Kelly. Differential Diagnosis for Physical Therapists: Screening for Referral. 2007 ed. Vol. 4th Edition. St. Louis, Missouri: Saunders Elsevier, 2007. Print.  Keriakos, R, Bhatta, SR, Morris, F, Mason, S, and Buckley, S. Pelvic Girdle Pain During Pregnancy and Puerperium. J Obstet Gynaecol 31.7 (2011): 572-80. Print.  Rosenthal, H. E., W. R. Slaunwhite, Jr., and A. A. Sandberg. Transcortin: A Corticosteroid-Binding Protein of Plasma. X. Cortisol and Progesterone Interplay and Unbound Levels of These Steroids in Pregnancy. J Clin Endocrinol Metab 29.3 (1969): 352- 67. Print.