To observe the natural history of asymptomatic osteonecrosis of the femoral head, and to analyse the associations between the subsequent development of symptoms, epidemiological risk factors and the character of the lesions. Sixty-eight patients were diagnosed with asymptomatic osteonecrosis of the femoral head. The patients were classified based on the development of symptoms. Relations were sought between symptom development and epidemiological risk factors, and the size and location of the necrotic lesions. Thirty-eight patients developed symptoms (55.9%) at a mean 2.27 years after diagnosis. Symptoms developed in 18 of 28 patients with alcohol-related necrosis (64.3%), in eight of 14 patients with steroid-related necrosis (57.1%), and in 12 of 26 patients with idiopathic necrosis (46.2%). None of the following: gender, age, body mass index (BMI), smoking status, or cholesterol level, was found to be significantly associated with the development of symtoms in asymptomatic osteonecrosis of femoral head (ONFH). Duration and amount of exposure to steroid were not significantly associated with symptom development. In the groups of heavy alcohol drinkers, large necrotic lesions and laterally located lesions showed a higher prevalence of symptom development. Symptoms developed in 55.9% of asymptomatic osteonecrosis of the femoral head. Prevalence of symptom development was significantly higher in heavy alcohol drinkers and large-sized lateral lesions.
