Diagnosis
During the physical exam, your doctor is likely to:
* Inspect your knee for swelling, pain, tenderness, warmth and visible bruising
* Check to see how far you can move your lower leg in different directions
* Push on or pull the joint to evaluate the integrity of the structures in your knee

Imaging tests
In some cases, your doctor might suggest tests such as:
* X-ray. Your doctor may first recommend having an X-ray, which can help detect bone fractures and degenerative joint disease.
* Computerized tomography (CT) scan. CT scanners combine X-rays taken from many different angles to create cross-sectional images of the inside of your body. CT scans can help diagnose bone problems and subtle fractures. A special kind of CT scan can accurately identify gout even when the joint is not inflamed.
* Ultrasound. This technology uses sound waves to produce real-time images of the soft tissue structures within and around your knee. Your doctor may want to move your knee into different positions during the ultrasound to check for specific problems.
* Magnetic resonance imaging (MRI). An MRI uses radio waves and a powerful magnet to create 3D images of the inside of your knee. This test is particularly useful in revealing injuries to soft tissues such as ligaments, tendons, cartilage and muscles.
Lab tests
If your doctor suspects an infection or inflammation, you’re likely to have blood tests and sometimes a procedure called arthrocentesis, in which a small amount of fluid is removed from within your knee joint with a needle and sent to a laboratory for analysis.
Treatment
Treatments will vary, depending upon what exactly is causing your knee pain.
Medications
Your doctor may prescribe medications to help relieve pain and to treat the conditions causing your knee pain, such as rheumatoid arthritis or gout.
Therapy
Strengthening the muscles around your knee will make it more stable. Your doctor may recommend physical therapy or different types of strengthening exercises based on the specific condition that is causing your pain.
If you are physically active or practice a sport, you may need exercises to correct movement patterns that may be affecting your knees and to establish good technique during your sport or activity. Exercises to improve your flexibility and balance also are important.
Arch supports, sometimes with wedges on one side of the heel, can help shift pressure away from the side of the knee most affected by osteoarthritis. In certain conditions, different types of braces may be used to help protect and support the knee joint.
Injections
In some cases, your doctor may suggest injecting medications or other substances directly into your joint. Examples include:
* Corticosteroids. Injections of a corticosteroid drug into your knee joint may help reduce the symptoms of an arthritis flare and provide pain relief that may last a few months. These injections aren’t effective in all cases.
* Hyaluronic acid. A thick fluid, similar to the fluid that naturally lubricates joints, hyaluronic acid can be injected into your knee to improve mobility and ease pain. Although study results have been mixed about the effectiveness of this treatment, relief from one or a series of shots may last as long as six months.
* Platelet-rich plasma (PRP). PRP contains a concentration of many different growth factors that appear to reduce inflammation and promote healing. Some studies have found that PRP may benefit certain people with osteoarthritis, but more studies are needed.
Surgery
If you have an injury that may require surgery, it’s usually not necessary to have the operation immediately. Before making a decision, consider the pros and cons of both nonsurgical rehabilitation and surgical reconstruction in relation to what’s most important to you. If you choose to have surgery, your options may include:
* Arthroscopic surgery. Depending on your injury, your doctor may be able to examine and repair your joint damage using a fiber-optic camera and long, narrow tools inserted through just a few small incisions around your knee. Arthroscopy may be used to remove loose bodies from your knee joint, remove or repair damaged cartilage (especially if it is causing your knee to lock), and reconstruct torn ligaments.
* Partial knee replacement surgery. In this procedure, your surgeon replaces only the most damaged portion of your knee with parts made of metal and plastic. The surgery can usually be performed through small incisions, so you’re likely to heal more quickly than you are with surgery to replace your entire knee.
* Total knee replacement. In this procedure, your surgeon cuts away damaged bone and cartilage from your thighbone, shinbone and kneecap, and replaces it with an artificial joint made of metal alloys, high-grade plastics and polymers.
* Osteotomy. This procedure involves removing bone from the thighbone or shinbone to better align the knee and relieve arthritis pain. This surgery may help you delay or avoid total knee replacement surgery.