One exercise for strengthening the knees is the hamstring curl, according to OrthoInfo. Other exercises include the straight-leg lift, the single leg dip, wall squats and step-ups. Medical professionals suggest individuals with bad knees also engage in low-impact conditioning exercises such as cycling and swimming, Healthline explains.
Exercise beneficial for bad knees includes both strengthening and stretching, reports OrthoInfo. Keeping the muscles around the joint strong and the ligaments flexible helps stabilize and protect the knee joint.
An individual who suffers from weak knees or knee pain should consult a doctor or physical therapist before beginning an exercise program, start slowly and take care not to overwork the area, notes OrthoInfo.