Avulsion of muscles from the femoral trochanter in the fowl.

Post-mortem examination revealed lateral femoral trochanteric defects in 14 out of 104 broiler type chickens. All birds were severely lame, and in the absence of concomitant musculoskeletal disease trochanteric lesions were implicated in their clinical signs. Trochanteric muscle insertions had avulsed and the lateral metaphyseal defect was usually lined with granulation tissue. Examination of normal trochanteric development identified endochondral ossification at sites of muscle attachment. In some skeletally immature, proximal femurs evidence of osteochondrosis was detected at sites of trochanteric muscle attachment. It is deduced that broiler femoral trochanters are susceptible to muscle avulsion by virtue of their known predisposition to osteochondrosis and the pattern of muscle insertion.