·	Some knee problems, such as those resulting from an accident, cannot be foreseen or prevented. However, a person can prevent many knee problems by following these suggestions:

·	First warm up by walking or riding a stationary bicycle, then do stretches before exercising or participating in sports. Stretching the muscles in the front of the thigh (quadriceps) and back of the thigh (hamstrings) reduces tension on the tendons and relieves pressure on the knee during activity.

·	Strengthen the leg muscles by doing specific exercises (for example, by walking up stairs or hills, or by riding a stationary bicycle). A supervised workout with weights is another pathway to strengthening leg muscles that benefit the knee.

·	Avoid sudden changes in the intensity of exercise. Increase the force or duration of activity gradually.

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Wear shoes that both fit properly and are in good condition to help maintain balance and leg alignment when walking or running. Knee problems may be caused by flat feet or overpronated feet (feet that roll inward). People can often reduce some these problems by wearing special shoe inserts (orthotics). Maintain appropriate weight to reduce stress on the knee. Obesity increases the risk of degenerative (wearing) conditions such as osteoarthritis of the knee.

·	The medial collateral ligament (MCL) provides stability to the inner (medial) aspect of the knee.

·	The lateral collateral ligament (LCL) provides stability to the outer (lateral) aspect of the knee.

·	The anterior cruciate ligament (ACL), in the center of the knee, limits rotation and the forward movement of the tibia.

·	The posterior cruciate ligament (PCL), also in the center of the knee, limits backward movement of the tibia.

·	Medical history—the patient tells the doctor details about symptoms and about any injury, condition, or general health problem that might be causing the pain.

·	Physical examination—the doctor bends, straightens, rotates (turns), or presses on the knee to feel for injury and discover the limits of movement and location of pain.

·	Diagnostic tests—the doctor uses one or more tests to determine the nature of a knee problem.

·	X ray (radiography)—an x-ray beam is passed through the knee to produce a two-dimensional picture of the bones.

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Computerized axial tomography (CAT) scan—x rays lasting a fraction of a second are passed through the knee at different angles, detected by a scanner, and analyzed by a computer. This produces a series of clear cross-sectional images ( slices”) of the knee tissues on a computer screen. CAT scan images show soft tissues more clearly than normal x rays. Individual images can be combined by computer to give a three-dimensional view of the knee.

·	Bone scan (radionuclide scanning)—a very small amount of radioactive material is injected into the patient's bloodstream and detected by a scanner. This test detects blood flow to the bone and cell activity within the bone, and can show abnormalities in these processes that may aid diagnosis..

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Magnetic resonance imaging (MRI)—energy from a powerful magnet (rather than x rays) stimulates tissues of the knee to produce signals that are detected by a scanner and analyzed by computer. This creates a series of cross-sectional images of a specific part of the knee. An MRI is particularly sensitive for detecting damage or disease of soft tissues, such as ligaments and muscles. As with a CAT scan, a computer can be used to produce three-dimensional views of the knee during MRI.

·	Arthroscopy—the doctor manipulates a small, lighted optic tube (arthroscope) that has been inserted into the joint through a small incision in the knee. Images of the inside of the knee joint are projected onto a television screen.