Ans. is 'd' i.e., Unknown PEHE'S DISEASE (LEGG-CALVE PEHE'S DISEASE) Pehe's disease is also known as osteochondritis deformans juvenilis or Coxa piano or Pseudocoxalgia. Pehe's disease is an osteochondritis of the epiphysis of the femoral head (capital femoral epiphysis). In the disease, the femoral head becomes paly or wholly avascular and deformed. The disease occurs commonly in males in the age group of 5-10 years. Etiology of Pehe's disease Pehe's disease is the most common form of osteochondroses (osteochondroses are characterized by avascular necrosis (AVN) and defective endochondral ossification of primary or secondary ossification centers). The etiology remains unknown, but is currently accepted that the disorder is caused by an interruption of the blood supply to the capital femoral epiphysis, causing avascular necrosis. Clinical features of Pehes disease Pehes disease is common in male of age group 5-10 years. Pain in the hip, often radiating to knee. Limp (antalgic limp). Limitation of movement :- Abduction, internal rotation and extension are limited, therefore there is adduction, external rotation, and flexion deformity. Shoening of limb. Positive trendelenburg test. During the disease process, bone age is 1-3 years lower than the normal. After healing, bone age returns to normal. Radiological investigations for Pehe's disease Following radiological investigations are used : 1) X-ray hip Findings are :- Increased medial joint space Widening of femoral neck Lateral extrusion (lateral subluxation) Metaphyseal cysts and rarefaction of metaphysis Horizontal physis with speckled calcification lateral to it Fragmentation of femoral head with increased density (irregular densities in the epiphysis) 2) Bone scan May show a decrease uptake by femoral head. 3) MRI It is the investigation of choice as it can diagnose Pehes disease in early stages when X-ray is normal. MRI tells about :- Extent of area involved Sphericity of the head Subluxation of the head Thus MRI helps better in planning for management.