Knee pain is a very common symptom, and should be worked up should the pain reach the severe level. The first and foremost is to identify the cause of the knee pain. There are many reasons, including wear and tear of the cartilage (arthritis), meniscus or tendon problems etc. It would be best to seek a consultation with an orthopaedic doctor first to diagnose the cause of the pain. This would include a thorough clinical history and physical examination. Radiological investigations like X-rays and MRIs may also be indicated.
Depending on what the diagnosis is, treatment can range from conservative (medication, physiotherapy- stretching, strengthening, ultrasound therapy, taping etc)) to injections or even surgery (arthroscopy (keyhole) or open).
Hope this helps
Kind regards
Dr Sean Ng