58 years old female c/o pain in right hip for past for past 2 years, and c/o difficulty in walking and c/o radiating pain to right knee. No H/o trauma, no H/o steroid intake, no H/o fever. O/E: No Fixed Deformity, no h/o swelling, Tenderness in the Rt hip joint, full flexion restricted, antalgic gait.

Investigation: CBC, TLC-5,600, N-55%, L-39%, E-04%, Peripheral smear-No sickling , ESR-50 mm/hour. Mx-Negative, RA-Negative,  Discuss the probable etiology of this AVN Rt HIP? Planned for THR.