In the earliest stage of the disease, x-rays appear normal and the diagnosis is made using MRI. The advanced stages of osteonecrosis begin when the dead bone starts to fail mechanically through a process of microfractures of the bone. As the disease progresses, the surface begins to collapse until, finally the integrity of the joint is destroyed. A wide range of surgical treatments with variable success rates have been proposed for the treatment of the osteonecrosis to preserve joint integrity, including core decompression, whereby the venous hypertension that ensues is lessened and revascularisation may be induced leading to bone repair. Nonsurgical treatment options are limited and usually result in a poor prognosis. Early stage disease can be treated with protected weight bearing and physiotherapy, however some studies have shown protected weight bearing to be associated with a greater than 85% rate of femoral head collapse. Unfortunately most studies indicate that the risk for disease progression is greater with nonsurgical treatment than with surgical intervention. There are no established pharmaceuticals for the prevention of treatment of osteonecrosis. Evidence is increasing that the nitrogen containing bisphosphonates may be beneficial in the treatment of osteonecrosis. One bisphosphonates (alendronate) has been evaluated in 60 patients diagnosed with osteonecrosis of the hip. Recent clinical studies have shown very promising results. All patients had symptomatic improvement after one year. Although the follow up time ranged from 3 months to 5 years, only 6 patients progressed to the point of needing surgery.