Knee pain can result from several causes, the most commonly being degeneration of the lining cartilage (also known as osteoarthritis), tears of the specialized shock-absorbing cartilage (known as the meniscal tears). ligament injury leading to joint instability and inflammation of the muscles and tendons around the knee joint.  In addition, problems of the spine and hip joints can occasionally manifest as knee pain as well.

For most musculoskeletal conditions, a non-surgical approach will be able to manage the majority of patients. This would include physiotherapy which your friend is undergoing and also pharmaceutical agents such as pain-killers, anti-inflammatory drugs and glucosamine supplements. Most often, some improvement of your friend’s symptoms should be felt after 4 to 6 sessions of therapy. If no improvement is noted, your doctor may consider complementing the physiotherapy with some medication.

Currently in practice, viscosupplementation in which a gel-like substance consisting of hyaluronic acid is injected into the arthritic knee for pain relief is occasionally performed. This procedure, however, is able to only bring about temporary relief (usually from 3 to 12 months) and varies from patient to patient.

From you description of your symptoms, it seems that you have developed degeneration of the cartilage lining between the undersurface of your knee cap and the front of the lower end of your thigh bone.

This is known as patellofemoral osteoarthritis. This leads to the clicking when you move your knee as the cartilage is no longer smooth, and is frequently associated with increased knee joint fluid production also known as an effusion. I would recommend you be referred to see an orthopaedic specialist who could confirm this diagnosis and request for some xrays of your knees to help guide subsequent management.