Some studies demonstrate that children with Perthes disorder are euthyroid and have elevated levels of free thyroxine and free triiodothyronine. In addition, the extent of femoral head involvement has been found to correlate with increases in free thyroxine. On biopsy, Perthes disorder is characterized by osteonecrosis and subsequent repair of the capital femoral epiphysis. Abnormal blood viscosity and clotting have been documented in children with Perthes disorder and are proposed as possible contributory factors in this disorder. The pain may be localized to the groin, but frequently, just as with slipped capital femoral epiphysis and other hip disorders, the pain may be present in the region of the thigh or knee.
Children presenting with knee pain always require a thorough examination of the hip.
The pain is frequently insidious and intermittent. In many cases, the child does not complain of pain, but teachers or family members note a persistent limp. The pain and limp are frequently activity related and may have offered as a possible cause of the child s distress and delay of diagnosis. The limp may be either pronounced or subtle. The gait abnormality may be secondary to pain, a limb length discrepancy, or an abnormal range of motion.