Knee pain is common in people who are otherwise fit and active. However, it is rare that the knee is the cause of the problem. It is normally the unwitting victim of failures and problems elsewhere in the body.
The knee is a slightly modified hinge joint that has only a limited ability to compensate for circular and sideways forces. Poor foot mechanics, collapsing arches and inadequate gluteal muscles or problems of muscular balance in the thigh are often to blame for knee problems. The knee joint is also prone to Osteoarthritis which is linked to genetics, obesity and general wear and tear, it may also provide an early indication that the hip joint is suffering from arthritis, as this is a common area of referral for hip osteoarthritis.
A standard set of orthopaedic tests will generally show what is wrong with the knee itself. However, the underlying cause is generally due to something failing to work correctly elsewhere. I will generally perform a full assessment of your gait, with video analysis of your foot and leg mechanics. This will often show up problems that are resulting in knee pain