Knee problems are very common, and they occur in people of all ages.
The knee is the joint where the bones of the upper leg meet the bones of the lower leg, allowing hinge-like movement while providing stability and strength to support the weight of the body. Flexibility, strength, and stability are needed for standing and for motions like walking, running, crouching, jumping, and turning.
Several kinds of supporting and moving parts, including bones, cartilage, muscles, ligaments, and tendons, help the knees do their job. Each of these structures is subject to disease and injury. When a knee problem affects your ability to do things, it can have a big impact on your life. Knee problems can interfere with many things, from participation in sports to simply getting up from a chair and walking.
Causes of Knee Problems
Knee problems can be the result of disease or injury.
A number of diseases can affect the knee. The most common is arthritis. Although arthritis technically means “joint inflammation,” the term is used loosely to describe many different diseases that can affect the joints.
Knee injuries can occur as the result of a direct blow or sudden movements that strain the knee beyond its normal range of motion. Sometimes knees are injured slowly over time. Problems with the hips or feet, for example, can cause you to walk awkwardly, which throw off the alignment of the knees and leads to damage. Knee problems can also be the result of a lifetime of normal wear and tear. Much like the treads on a tire, the joint simply wears out over time. This booklet discusses some of the most common knee injuries, but first describes the structure of the knee joint.
Diagnosis of Knee Problems
Doctors diagnose knee problems based on the findings of a medical history, physical exam, and diagnostic tests.
During the medical history, the doctor asks how long symptoms have been present and what problems you are having using your knee. In addition, the doctor will ask about any injury, condition, or health problem that might be causing the problem.
The doctor bends, straightens, rotates (turns), or presses on the knee to feel for injury and to determine how well the knee moves and where the pain is located. The doctor may ask you to stand, walk, or squat to help assess the knee’s function.
Depending on the findings of the medical history and physical exam, the doctor may use one or more tests to determine the nature of a knee problem. Some of the more commonly used tests include:
- X ray (radiography). A procedure in which an x-ray beam is passed through the knee to produce a two-dimensional picture of the bones.
- Computerized axial tomography (CT) scan. A painless procedure in which x rays are passed through the knee at different angles, detected by a scanner, and analyzed by a computer. CT scan images show soft tissues such as ligaments or muscles more clearly than do conventional x rays. The computer can combine individual images to give a three-dimensional view of the knee.
- Bone scan (radionuclide scanning). A technique for creating images of bones on a computer screen or on film. Before the procedure, a harmless radioactive material is injected into your bloodstream. The material collects in the bones, particularly in abnormal areas of the bones, and is detected by a scanner.
- Magnetic resonance imaging (MRI). A procedure that uses a powerful magnet linked to a computer to create pictures of areas inside the knee. During the procedure, your leg is placed in a cylindrical chamber where energy from a powerful magnet (rather than x rays) is passed through the knee. An MRI is particularly useful for detecting soft tissue damage.
- Arthroscopy. A surgical technique in which 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.
- Joint aspiration. A procedure that uses a syringe to remove fluid buildup in a joint to reduce swelling and relieve pressure. A laboratory analysis of the fluid can determine the presence of a fracture, an infection, or an inflammatory response.
- Biopsy. A procedure in which tissue is removed from the body and studied under a microscope.