Knee injuries are injuries that cause temporary or chronic discomfort, pain, or loss of range of motion in the knee or knees.
The knee is the largest joint in the body. It is a hinge joint made up of several bones coming together supported by cartilage * , tendons * , and ligaments * . Fluid in the knee joint provides lubrication to keep the joint working properly. The major bone of the knee is the patella or kneecap. The lower part of the femur * , the upper part of the tibia * , and the patella come together at the knee. The knee moves in two ways: flexion * and extension * . Healthy bones, tendons, and ligaments enable the knee to move in support of walking, running, and all the activities that require effective movement of the knee. Fractures (breaks) or dislocations (displacement or abnormal positioning) of the bone, tears in the tendons or ligaments, or abnormal stretching of the tendons and ligaments can cause damage to the knee and interfere with movement. Problems in moving can include sitting down and getting up, walking and running, or participating in sports.
Knee injuries are common and affect people of all ages, especially those involved in high-impact sports. According to the American Academy of Orthopedic Surgeons, there are approximately 11 million doctor visits related to fractures, dislocations, sprains, and ligament tears each year in the United States.
While anyone can experience a knee injury, athletes involved in intense physical activity or contact sports are at increased risk.
The primary sign of a knee injury is pain in and around the knee. The pain may be so severe that the person is unable to stand or place any weight on the injured leg. Swelling of the knee occurs, and the knee may become warm to the touch. The knee joint may be unstable or looser than normal. There may be a creaking sound when the person moves the knee. In a fracture or dislocation, the patella (kneecap) may be in an abnormal position off to one side of the knee instead of centered securely on top of the knee.
To diagnose a knee injury, the healthcare provider takes a complete health history and asks specific questions about any activity or accident that might have caused injury to the knee, pain in the knee, flexibility, and general ability to move and put weight on the knee, as is required for standing and walking. The doctor performs a physical examination of the knee by touching (palpating * ) the different areas of the knee to determine whether swelling or abnormal movement are present and observing the knee during movement. X-rays of the knee and a special test called an MRI * (magnetic resonance imaging) may be ordered. These tests provide an image of the bones, cartilage, and ligaments to determine the location and severity of any specific injury. A person with a knee injury may be referred to a physician with specialized knowledge of and experience in treating knee injuries, either an orthopedist or a specialist in sports medicine.
Knee injuries can be prevented by maintaining strength and flexibility in the muscles and ligaments that support the knee, and by keeping one's weight within the recommended guidelines for one's age, height, and gender. If the knee is determined to be a “loose” knee, wearing a knee brace may prevent injury. Wearing the proper shoes for the activity, as well as avoiding risky behaviors to prevent falls and motor vehicle accidents, can also prevent knee injury. In addition, checking one's house or apartment for such hazards as loose rugs, badly placed furniture, poorly maintained stairs, and similar problems can also help to prevent knee injuries from tripping or falling.
See also Arthritis • Broken Bones (Fractures) • Foot Disorders: Overview • Obesity • Osgood-Schlatter Disease • Repetitive Stress Syndrome • Sports Injuries: Overview • Strains and Sprains • Tendinitis
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* cartilage (CAR-te-lej) is the tough, flexible tissue that covers the ends of the bones.
* extension (eks-TEN-shun) is the movement of a joint that brings the parts of a limb (e.g., arms, legs, or spine) into a straight line, or increases the angle of a joint.
* flexion (FLEK-shun) is the act of bending or the state of being in a bent position, as well as a decrease in the angle of the bones forming a joint.
* tibia (TIB-ee-ya) is the longer of two bones in the lower leg that connects with the knee above and the ankle below.
* femur (FEE-mur) is the long bone of the upper leg.
* ligaments (LIG-a-ments) are bands of fibrous tissue that connect bones or cartilage, supporting and strengthening the joints.
* tendons (TEN-dons) are fibrous cords of connective tissue that attach a muscle to a bone or other structure.
* autoimmune relates to a disease in which the body's immune system attacks some of the body's own normal tissues and cells.
* degenerative (dee-JEN-er-uh-tiv) means progressively worsening or becoming more severely impaired.
* chronic (KRAH-nik) is a condition that lasts a long time or recurs frequently.
* menisci (men-IS-key) is the fibrocartilage-like tissue found in some joints. The singular form is meniscus (men-IS-kus).
* obese (oh-BEESS) means an excess of body fat. People are considered obese if they weigh more than 30 percent above what is healthy for their height.
* palpation (pal-PAY-shun) is the examination by touching and feeling the body for indicators of disease or injury.
* MRI is the abbreviation for magnetic resonance imaging, which produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.
* physical therapy is a healthcare profession responsible for assisting people with impairment or limitation of movement. Physical therapists design treatment and exercise programs to decrease pain, strengthen muscles, improve flexibility, and increase physical endurance.
* corticosteroids (KOR-tih-ko-STEroyds) are medications that are given to people to treat inflammatory diseases. They are also chemical substances made by the adrenal glands that have several functions in the body, including maintaining blood pressure during stress and controlling inflammation.
* arthroscopic (AR-thro-SKOP-ik) surgery, also called arthroscopy, is the insertion of a specialized device called an endoscope to examine and treat the inside of a joint.