Muscle weakness (thigh muscles) is the most important reason for knee pain. As, after 40 years of age, our muscles start getting weak by 8-10% every 10 years. Weak muscles are not able to take on the body weight and this directly exerts stress on articular cartilage and knee joint. Osteoarthritis is most commonly caused by muscle weakness.
Symptoms are helped in making the diagnosis because muscle weakness is quite clear with symptoms.
Muscle weakness due to other medical condition or disease, then underlying cause needs to be treated.