According to a new research, 90 percent of people with knee osteoarthritis wait too long to have a replacement. A new algorithm has been developed by experts to assist physicians and patients in determining the best timing for surgery. The algorithm takes into account factors such as age, gender, weight, joint space narrowing, and symptoms to help make the most informed decision possible. Replacement surgeries are very successful at relieving pain and improving function, but they cannot restore normal anatomy or physiology. Patients who have not had any improvement in symptoms after making changes such as losing weight or changing their lifestyle should consider replacement surgery.