The five most common knee problems are arthritis, tendonitis, bruises, cartilage tears, and damaged ligaments. Knee injuries can be caused by accidents, impact, sudden or awkward movements, and gradual wear and tear of the knee joint.
Because the knee joint is both vulnerable and used extensively in many activities, it is prone to injuries. The American Academy of Orthopaedic Surgeons estimates that 19.5 million visits to doctors' offices in 2002 were for knee problems. In some sports including football, skiing, and gymnastics, and racket sports, injury rates to avid practitioners can near 50 percent, and knee injuries are the most common reason patients visit orthopedic doctors. An estimated one in five runners gets a knee injury. The majority of knee injuries, however, are minor and do not require intensive treatment.
The knee, the largest joint in the body, connects the thighbone (femur) to the lower leg (tibia). It is a complex and efficient joint consisting of ligaments, cartilage, and the bone of the kneecap (patella). All of these parts can be injured. Inside the knee joint is synovial fluid that protects and lubricates the parts, which during injuries may increase and cause swelling. The bursa are sacs in the knee that contain synovial fluid and provide cushioning and lubrication.
Four ligaments comprise the knee joint. The medial collateral ligament (MCL) runs along the inside of the knee, while the lateral collateral ligament (LCL) is on the outside of the knee. The cruciate ligaments cross inside the knee. The anterior cruciate ligament (ACL) is deep inside the knee and limits rotation of the joint. The posterior cruciate ligament (PCL) is also inside the knee and limits the backward movement of the joint. Ligaments in the knee can be partially or completely torn, depending on the extent of the injury.
The minisci cartilage are two thin, oval-shaped tissues that act as cushions between the ends of the leg bones. The medial miniscus is the cartilage closest to the other leg while the lateral miniscus is nearer the outside of the knee. Injuries to the minisci include tears from injuries and impact and degenerative wearing away of the structure. The minisci can be partially or completely torn during injury.
The bones around the knee, including the kneecap, can be broken, fractured, or chipped. The patellar tendon connects the kneecap to the shinbone, while the quadriceps tendon connects the quadriceps muscle to the patella. The patellar tendon can be torn or can develop injury and pain from degeneration. It can also be fully dislocated or partially dislocated (called subluxation). The tendons in the knee may develop pain and inflammation known as tendonitis.
The bones of the knee joint are covered with tissue known as articular cartilage. This cartilage can be injured or fractured, and can also develop a degenerative condition called chondromalacia. Osteoarthritis is the pain associated with the wearing down of this cartilage.
Causes & symptoms
Arthritis may develop from an auto-immune disorder, known as rheumatoid arthritis, or may be caused by the gradual wear and tear of the joint, known as osteoarthritis. Symptoms of arthritis in the knee include pain ranging from dull aches to severe pain, and may be accompanied by swelling and range of movement loss. Arthritic symptoms may tend to be worst in the morning and decrease throughout the day as the knee is used. Arthritis can be caused by lupus, Lyme disease, and other infections. Knee swelling also may be caused by bursitis, the inflammation of the bursa.
Cartilage injuries may include chondromalacia, with symptoms including dull pain and pain while climbing stairs. Damage to the minisci cartilage often occurs from sudden twists, forceful plants, and awkward movements. A torn cartilage may make a popping sound, and may be accompanied by mild to severe pain, particularly while straightening the leg. Swelling, stiffening, and loss of movement are also symptoms of cartilage tears, as are clicking sounds and friction in the knee during movement.
Ligament injuries may cause dull or severe pain, swelling, loss of the range of movement of the joint, and loss of the stability and strength of the knee. Ligament injuries typically occur from strong blows and forces applied to the knee. Injuries to the MCL are the most common, often caused by impact to the side of the knee joint. Of the cruciate ligaments, the PCL is less commonly injured than the ACL. Typically, the PCL is injured by forceful blows to the knee, such as during car accidents, while the ACL can be injured by impacts and by sudden twists. Torn ligaments may be accompanied by a popping sound indicating the rupture, and may not always cause pain, so that some of them go unnoticed. Torn ligaments may weaken the knee and cause buckling or folding under weight.
Tendon injuries range from tendonitis to torn tendons. Symptoms of tendonitis include pain and swelling, while ruptured tendons can cause more intense pain, swelling, and loss of movement.
Osgood-Shlatter disease is a condition common in young boys who play running and jumping sports. Symptoms include inflammation of the patellar tendon and pain in the front of the knee during and after strenuous activity.
Iliotibial band syndrome is common in running and other repetitive sports, characterized by pain at the side of the knee caused by stress on the band of tendons there. Sometimes this condition causes a snapping sensation when the knee is straightened.
Depending on the severity of the condition, family physicians or orthopedic physicians who specialize in the knee joint may be consulted. If arthritis is suspected, a rheumatologist may be consulted. The diagnosis process includes taking a complete patient history with details of the pain and the circumstances of the injury. The physician will give the patient a thorough physical examination, including utilizing several manual techniques of moving the knee joint and legs in various positions to help determine the type of injury. An experienced practitioner can often make an accurate diagnosis of injuries by performing a sequence of manual diagnostic tests.
Laboratory tests may be ordered to further or clarify the diagnosis. X rays can show damage to the bones as well as the narrowing of the knee space that may imply cartilage problems. For more in-depth diagnosis, a computerized axial tomographic (CAT) scan is an x-ray technique that can provide three-dimensional views of the bones in the knee. A magnetic resonance imaging (MRI) scan gives a computerized portrait of the interior of the knee, and may show damage to the ligaments and cartilage. Arthroscopy is a form of minor surgery that inserts a tiny camera into the knee and gives a very accurate view of the joint. Radionuclide scanning (bone scans) use radioactive material injected into the bloodstream to monitor the blood flow in particular areas. If infection or rheumatoid arthritis is suspected, a physician may order blood tests for diagnosis. Biopsies, in which pieces of tissue are laboratory tested, may also be used for diagnosis.
When a person suspects a knee injury, the first treatment recommended is R.I.C.E., which stands for rest, ice, compression, and elevation. First, the person should cease the activity which caused the injury and immediately rest and immobilize the joint. Ice may be applied to reduce pain and swelling, and compression, such as wraps and braces, may be used to immobilize the knee. Elevating the leg is also helpful in reducing swelling and aiding circulation. Immediate care will prevent the worsening of the injury.
Treatment options for knee injuries can range from rest and light activity, to physical therapy, to surgery. Most knee injuries are treated with proper rest, exercise, and strengthening programs recommended by physicians. For injuries that require surgery or deeper diagnosis, arthroscopy is the least invasive technique and has a quick recovery time associated with the procedure. Arthroscopy is commonly used to repair cartilage and partially torn ligaments. For severe knee injuries, reconstructive surgery or open knee surgery may be required. Full knee replacements may also be performed for severely damaged knees. After surgery, physical therapy programs for rehabilitation are recommended. Treatment for osteoarthritis includes over-the-counter painkillers, exercise, and weight reduction. For rheumatoid arthritis, more powerful prescription medications, such as steroids and stronger painkillers, and intensive physical therapy may be ordered. Knee injuries associated with infection may require antibiotics.
Alternative therapies for knee injuries focus on supporting the body's ability to heal itself. Various therapies may include bodywork and postural adjustments such as chiropractic and Rolfing work, in addition to physical therapy and gentle exercise routines. Herbal remedies and nutritional supplements may be used to aid the healing process and reduce symptoms. Acupuncture may be used for pain relief, and yoga is a low-impact exercise routine that increases flexibility, good alignment, and strength.
The best prevention for knee injuries is being aware of activities that carry high risks for knee injuries and acting carefully. The knees can be strengthened by evenly building the muscles in the quadriceps and hamstrings. Increasing flexibility in the body through stretching can also help reduce injuries. Properly fitting shoes and other sports equipment are essential for preventing injury as well. Finally, before engaging in activities that stress the knee, a thorough and gradual warm-up routine, including aerobic activity and stretching, will lessen the chances of knee injury.
Grelsamer, Ronald, M.D. What Your Doctor May Not Tell You about Knee Pain and Surgery. Warner Books, 2002.
Halpern, Brian. The Knee Crisis Handbook. Rodale Books, 2003.
Scott, W. Norman. Dr. Scott's Knee Book. Fireside Books, 1996.
American Physical Therapy Association. 1111 North Fairfax St., Alexandria, VA 22314-1488. (703) 684-2782. 〈http://www.apta.org〉.
Lupus— Chronic inflammatory disease caused by immune system disorder.
Lyme disease— Bacteria infection spread by ticks.
Orthopedist— Physician specializing in the diagnosis and treatment of problems involving the skeletal system.
Rheumatologist— Physician specializing in the diagnosis and treatment of arthritis and related conditions.