The Knee

Jump, stand, run and pivot - simple tasks, which require the help of the largest joint in our body - the knee. The knee, according to the American Academy of Orthopaedic Surgeons (AAOS), is one of the most easily injured joints in the human body. AAOS says that almost 11 million people visit doctors every year because of knee problems. More than half of those, about 6 million, are visits to orthopaedic surgeons who do more work on knees than any other part of the body.

The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) says the knee works like a hinge helping to bend and straighten the lower leg. The knee joint, according to NIAMS is the meeting place of three bones:

• the femur (lower end of the thighbone)
• the tibia (upper end of the shinbone)
• the patella (knee cap)

The patella sits over the other bones and slides in a groove on the end of the femur. Other parts of the knee include:

• cartilage (which acts like a cushion and absorbs shock)
• tendons (tough cords of tissue that connect muscle to bone)
• ligaments (elastic bands of tissue that connect bone to bone)

Ligaments are vulnerable to pulling, stretching and tearing. When it happens, it is called a sprain. (Read about "Sprains")

NIAMS says there are four major ligaments that surround the knee joint, keeping it in place when the leg is bent or straight:

• the anterior cruciate ligament (ACL) (center of knee)
• the posterior cruciate ligament (PCL) (center of knee)
• the lateral collateral ligament (LCL) (outer knee)
• the medial collateral ligament (MCL) (inner knee)

Below find information about problems that can develop in our knees.

Anterior Cruciate Ligament (ACL) Injury

The anterior cruciate ligament, according to AAOS, is crucial in keeping the shinbone from sliding beneath the thighbone; it is frequently injured among athletes who take part in skiing, basketball and football and those who wear cleated shoes.

According to AAOS, the ACL can be torn or injured in a variety of ways:

• quickly twisting or changing direction
• slowing down while running
• direct hit (like a football tackle)
• landing after a jump

Men and women alike can suffer from sports related injuries like ACL tears, but according to AAOS, data collected since 1995 reveals an injury pattern different for men and women who take part in the same sport. For example, AAOS says ACL injuries among women basketball players are twice that of their male counterparts. Women who play soccer are four times more likely to suffer from an ACL tear than men who play the same sport.

Part of the problem, according to AAOS, is the way many women jump, turn and pivot. They don't usually bend their knees as much as men do when landing from a jump. That, according to AAOS, puts increased pressure on the knee joint.

Many women also are in a more erect position when turning and pivoting. That also can strain the ACL. Learning to crouch and bend at the knees and hips, according to AAOS, could take some of the stress off the ACL.

If you suffer from an ACL injury, you may not even realize it right away. NIAMS says, at first, you may just hear a popping noise and feel your knee give out from under you. Two to twelve hours later, there will be swelling accompanied by pain. AAOS warns that walking or running on an injured ACL can damage the knee's cartilage.

See treatment options below.

Posterior Cruciate Ligament (PCL) Injury

If you suffer from a PCL injury, the shinbone can sag backwards, disrupting the stability of the knee joint. AAOS says the ends of the thighbone and shinbone will then rub directly against one another, weakening cartilage. This abrasion can lead to arthritis (Read about "Arthritis and Rheumatic Diseases") of the knee. Once again, athletes are susceptible to PCL injuries according to AAOS, though the PCL is not injured as frequently as the ACL. AAOS says PCL sprains usually occur because of:

• blow to the front of the knee
• misstep
• ligament was pulled or stretched too far

NIAMS says that the PCL is the one injured most often by blows such as football tackles or auto accidents.

NIAMS describes the symptoms of a PCL injury as being very similar to that of an ACL injury. That's because both involve a cruciate ligament. You may hear a pop and the leg may begin to buckle if you try to stand on it. AAOS says patients with PCL tears do not usually have symptoms of instability in their knees and can often return to activity after a rehabilitation program. (Read about "Rehabilitation")

See treatment options below.

Medial Collateral Ligament (MCL) Injury

The medial collateral ligament (MCL) attaches the thighbone to the shinbone. AAOS says this makes the inner side of the knee stable. Those taking part in contact sports, like hockey and football, are most likely to suffer from an MCL injury.

NIAMS says the MCL is most often injured because of a blow to the outer side of the knee. That kind of hit can stretch and tear the ligament, according to AAOS, on the inner side of the knee. So even though the hit is on one side the injury occurs on the opposite side of the knee.

NIAMS describes the symptoms of an MCL injury as a popping and buckling sideways of the knee. Swelling and pain are also common. An MRI, according to NIAMS, helps diagnose this injury. (Read about "MRI - Magnetic Resonance Imaging")

See treatment options below.

Lateral Collateral Ligament (LCL) Injury

The lateral collateral ligament (LCL) connects the thighbone to the fibula and stabilizes the outer side of the knee. AAOS says the LCL is rarely injured.

See treatment options below.

Cartilage Injuries

Cartilage cushions your knee, and acts to absorb shock during movement. Torn cartilage, according to AAOS is experienced by many people.

When people talk about torn knee cartilage, they are usually talking about a meniscal tear. The meniscus, according to AAOS, is a wedge-like rubbery cushion where the major bones of your legs connect. The meniscus helps the knee carry weight, glide and turn. Athletes who are involved in contact sports are at risk for this tear because of the amount of twisting, turning and decelerating involved. AAOS says the tear often happens in connection with other injuries like a torn ligament (ACL). The elderly are also at risk due to wear and tear of the cartilage over time.

AAOS says a meniscal tear could begin with a popping sensation. When inflammation sets in you might feel:

• stiffness and swelling
• fluid (water on the knee)
• tenderness in the joint

Without treatment, AAOS says, part of the meniscus may loosen and drift into the joint causing your knee to lock. AAOS recommends visiting your doctor right away if you suspect you have a meniscal tear. Treatment, according to NIAMS, can range from muscle-strengthening exercises to surgery if pain persists.

See treatment options below.

Chondromalacia Patella

Chondromalacia patella, according to NIAMS, is the softening of the articular cartilage of the kneecap. The disorder, NIAMS says, is often experienced among young adults and may be caused by a number of things:

• trauma
• overuse
• weakness
• misalignment of knee structure

Sufferers of chondromalacia patella often experience a dull pain around the knee, which seems to worsen when walking down stairs or hills. NIAMS says it may also be painful to bear weight on the knee when it's straightened. The disorder is often seen, according to NIAMS, in runners, skiers, soccer players and cyclists.

Muscle strengthening exercises, electrical stimulation and surgery are all possibilities, according to NIAMS, when treating chondromalacia patella.

See treatment options below.

Knee Arthritis

Arthritis (Read about "Arthritis and Rheumatic Diseases") of the knee, according to NIAMS, is usually a degenerative disease called osteoarthritis in which cartilage in the joint gradually wears down. (Read about "Osteoarthritis") Arthritis can affect not only the joint, but also all of its supporting structures like muscles, tendons and ligaments. NIAMS says it can be caused by:

• excess stress on the joint
• being overweight (Read about "Obesity" "Losing Weight")
• deformity
• genetics
• old injuries such as torn cartilage or torn ACL

Osteoarthritis most often affects middle-aged and older people, according to NIAMS. Those who experience it when they are young may have an inherited form of the disease. A common symptom according to NIAMS is morning stiffness that lessens after moving around. Other symptoms include pain, swelling and a decrease in range of motion.

Treatment can range from over-the-counter medications, like aspirin or acetaminophen, to mild exercise and in serious cases knee replacement surgery. (Read about "Joint Replacement" "Joint Resurfacing") Talk to your doctor about what's best for your specific problem.

Though not a treatment for arthritis, NIAMS says a new experimental procedure is currently being used to repair cartilage injuries at the end of the femur at the knee. The patient's own cartilage cells are used in the process.

See treatment options below.

Iliotibial Band Syndrome

A common tendon injury, according to NIAMS is iliotibial band syndrome. This is an overuse inflammatory condition due to friction (rubbing) of a band of a tendon over the outer bone of the knee. Although iliotibial band syndrome may be caused by direct injury to the knee, it is most often caused by the stress of long-term overuse, such as sometimes occurs in sports training.

A person with this syndrome feels an ache or burning sensation at the side of the knee during activity. Pain may be localized at the side of the knee or radiate up the side of the thigh. A person may also feel a snap when the knee is bent and then straightened. Swelling is usually absent and knee motion is normal. The diagnosis of this disorder is usually based on the patient's symptoms, such as pain at the outer bone of the knee and exclusion of other conditions with similar symptoms.

NIAMS says usually iliotibial band syndrome disappears if the person reduces activity and performs stretching exercises followed by muscle-strengthening exercises. (Read about "Stretching and Health") In rare cases when the syndrome doesn't disappear, surgery may be necessary to split the tendon so it is not stretched too tightly over the bone.

See treatment options below.

Osgood-Schlatter Disease

Repetitive stress or tension on part of the growth area of the upper tibia can cause Osgood-Schlatter disease in growing children. The disease may also be linked to an injury, in which a tendon is stretched so much that it tears from the tibia taking a bone fragment with it. According to NIAMS, the disease most commonly affects active boys who are about 10 to 15 years of age.

NIAMS says people who have the disease may experience:

• pain below the knee joint that worsens with activity
• a painful bony bump below the knee cap
• a few months of pain which may recur

NIAMS says motion of the knee is usually not affected and the disease almost always disappears without treatment. Icing the knee, when the pain starts, can help relieve swelling and is sometimes used with stretching and strengthening exercises. (Read about "Stretching and Health")

See treatment options below.

Osteochondritis Dissecans

Osteochondritis dissecans results from a loss of the blood supply to an area of bone underneath a joint surface and usually involves the knee. The affected bone and its covering of cartilage gradually loosen and cause pain. This problem usually arises spontaneously in an active adolescent or young adult. It may be due to a slight blockage of a small artery or to an unrecognized injury or tiny fracture that damages the overlying cartilage. A person with this condition may eventually develop osteoarthritis. (Read about "Osteoarthritis")

NIAMS says a lack of a blood supply can cause bone to break down, a condition called avascular necrosis or osteonecrosis. (Read about "Osteonecrosis") The involvement of several joints or the appearance of osteochondritis dissecans in several family members may indicate that the disorder is inherited.

If normal healing doesn't occur, cartilage separates from the diseased bone and a fragment breaks loose into the knee joint, causing weakness, sharp pain and locking of the joint. An x-ray, MRI (Read about "X-rays" "MRI - Magnetic Resonance Imaging") or arthroscopy (Read about "Arthroscopy") can determine the condition of the cartilage and can be used to diagnose osteochondritis dissecans.

If cartilage fragments have not broken loose, a surgeon may fix them in place with pins or screws that are sunk into the cartilage to stimulate a new blood supply, according to NIAMS. If fragments are loose, the surgeon may scrape down the cavity to reach fresh bone and add a bone graft and fix the fragments in position. Fragments that cannot be mended are removed and the cavity is drilled or scraped to stimulate new cartilage growth. NIAMS says research is being done to assess the use of cartilage cell and other tissue transplants to treat this disorder. (Read about "Transplants")

See treatment options below.

Plica Syndrome

Plica syndrome occurs when plicae (bands of synovial tissue that line the joints) are irritated by overuse or injury. NIAMS says synovial plicae are the remains of tissue pouches found in the early stages of fetal development. As the fetus develops, these pouches normally combine to form one large synovial cavity. If this process is incomplete, plicae remain as four folds or bands of synovial tissue within the knee. Injury, chronic overuse or inflammatory conditions are associated with this syndrome.

People with this syndrome are likely to experience pain and swelling, a clicking sensation and locking and weakness of the knee. Because the symptoms are similar to those of some other knee problems, plica syndrome is often misdiagnosed. Diagnosis usually depends on excluding other conditions that cause similar symptoms.

According to NIAMS, the goal of treatment is to reduce inflammation of the synovium and thickening of the plicae. The doctor usually prescribes medicine such as ibuprofen to reduce inflammation. The patient is also advised to reduce activity, apply ice and an elastic bandage to the knee and do strengthening exercises. A cortisone injection into the plica folds helps about half of those treated. If treatment fails to relieve symptoms within 3 months, the doctor may recommend arthroscopic or open surgery to remove the plicae. (Read about "Arthroscopy")

See treatment options below.

Tendon Injuries

Tendons, according to NIAMS, are like rubber bands that can become worn and fragile when stretched too far. Knee injuries involving tendons range from an inflammation of the tendons called tendinitis, (Read about "Tendinitis and Bursitis") to a ruptured tendon. (Read about "Strains") NIAMS says athletes and older people whose tendons are weaker are more prone to these injuries.

People with tendinitis, according to NIAMS often have tenderness and pain while running or jumping.

A ruptured tendon could result in difficulty bending, extending or lifting the leg and swelling.

Talk to your doctor about the best possible treatment for your condition. You physician, according to NIAMS, may ask you to rest, elevate, apply ice and take pain relievers to get you back on your feet. NIAMS says surgery might be necessary for a complete rupture of the quadriceps or patellar tendon.

See treatment options below.

Diagnosis and Treatment Options

If you suspect a knee injury, there are several tests that can help determine the cause and extent of the problem.

• X-rays can be used to rule out fractures. (Read about "X-rays")
• Magnetic resonance imaging can create images of both hard and soft tissues, and so can spot ligament or cartilage problems. (Read about "MRI - Magnetic Resonance Imaging")
• Ultrasound is another option. (Read about "Ultrasound Imaging")
• Arthroscopy (see below) may also be used, both to diagnose the problem, and to make repairs.

Whether you are currently suffering from a knee injury or knee pain, recovering from injury or trying to avoid it, there are many procedures and therapies that can help. The key, according to AAOS, is getting treatment as soon as possible. Options include:

• Physical therapy/rehabilitation - Physical therapy can help people either avoid surgery or recover following surgery. (Read about "Rehabilitation") It all starts with a careful assessment of your injury, according to the American Physical Therapy Association (APTA). The process, according to APTA will include:
  • Evaluation - identifying your condition and the factors that contributed to your injury.
  • Therapy - an individual plan designed to restore motion and muscle performance.
  • Education - your therapist might want to teach you some new habits to avoid another injury and overcome the one you have.
  • Aftercare - Physical therapy is aimed at getting you back on your feet with the knowledge of how to prevent reinjury so you won't need to visit your therapist again.

  A treatment plan may include a series of exercises like swimming, water walking, strengthening exercises and leg presses designed to help motion.

• RICE - which stands for rest, ice, compression, elevation
  • Resting the knee, according to AAOS, gives it time to heal. If you have to walk, AAOS suggests using crutches.
  • Ice, two to three times a day for about 20 minutes each time, according to AAOS, can control swelling.
  • Compressing the injury reduces swelling, according to AAOS. You may have to do this with an elastic bandage or brace that fits snugly, but loose enough so that it doesn't hurt.
  • Elevate the knee whenever possible says AAOS.

Sometimes surgery is needed to reduce knee pain and prevent further deterioration. Some surgical procedures that can be used include:

• Osteotomy - If you are younger than 60 and still fairly active, AAOS says osteotomy may be an option. In osteotomy, the surgeon reshapes the bone and the joint is repositioned, to correct alignment and compensate for damaged tissue. This can help to relieve pain. However, you may eventually need knee replacement surgery.
• Arthroscopy - Arthroscopy of the knee, according to AAOS, was first performed in the late 1960s. If you have persistent pain or swelling of your knee, your orthopaedic surgeon may recommend this procedure to relieve the problems. Arthroscopy allows the surgeon the opportunity to diagnose and treat knee disorders, according to AAOS. Using a pencil-sized device, called an arthroscope, small incisions are made into the knee. The scope transmits an image of your knee, which is projected onto a television screen. This clear view of the inside of the knee allows surgeons to find out what's causing your problem. Surgical instruments can also be inserted into other small incisions to remove or repair the damaged tissue. In many cases, arthroscopy can be used to repair:
  • torn or damaged cartilage
  • torn or damaged ligaments
  • loose bone fragments
  • damaged joint surfaces
  • synovial inflammation
  • knee instability or abnormal kneecap alignment

  Almost all arthroscopic knee surgery, according to AAOS, is done on an outpatient basis. (Read about "Arthroscopy")

• Knee replacement and resurfacing - Sometimes, rehabilitation and physical therapy aren't enough. (Read about "Rehabilitation") If the knee is severely damaged, and other measures don't bring relief, a doctor may suggest a knee replacement. (Read about "Joint Replacement") AAOS says that by resurfacing the knee's damaged and worn surfaces, knee replacement surgery can help reduce pain. Each year, over a quarter million knee replacements are performed in the United States. In a total knee replacement (TKR) or total knee arthroplasty (TKA), the surgeon first removes the damaged cartilage and bone. After that, the new joint surfaces are put in place. In general, AAOS says a total knee replacement is a two hour procedure, done under either general or spinal anesthesia. (Read about "Anesthesia") There are many different designs and brands of knee prostheses available, so you and your doctor should discuss your specific needs carefully. It's also important to remember that even an artificial joint can wear out over time, so sometimes a second surgery may be required down the road. There is also a procedure called unicompartmental knee arthroplasty (UKA) which may be appropriate for some people who are over age 60 and not very active. In a UKA, diseased bone is removed and replaced with an implant. AAOS says UKA can help alleviate pain and may delay the need for TKA. If damage is to only a portion of the knee, the patient may be a candidate for what is called a partial knee resurfacing (PKR) or partial knee replacement. PKR implants are smaller and less bone is impacted by the procedure. Some patients may also be candidates for minimally invasive knee replacement or robotic assisted surgery. (Read about "Robotic Surgery") These types of surgery involve smaller incisions and faster recoveries. However, they may not be appropriate for all patients, so you need to discuss them with your doctor.
• Ligament repair - Not all ligament issues require surgery. But if the ligament is completely torn, or torn in such a way that it cannot heal, surgery may be the best option. Surgery can be performed arthroscopically or traditional open surgery may be used. The surgery can use a strip of the patient's own tendon taken from another area to reconstruct the damaged ligament. Exercise and rehabilitation are used after surgery to restore mobility. Ligament surgery can often help to stabilize the knee, thereby allowing the patient to return to his or her activities in the same capacity as before surgery.
• Cartilage repair - Cartilage is the tissue that provides cushioning in the knee. If damage is extensive, torn cartilage can be repaired through surgery. Surgery to repair cartilage can be performed arthroscopically or traditional open surgery may be used. Other options include:
  • Meniscal transplant - The meniscus is a cushion of cartilage in the knee joint. If it is damaged or torn, younger patients may be candidates for a meniscal transplant. This procedure uses donor tissue to replace the damaged meniscus. It is not appropriate for all patients, however.
  • Autologous chondrocyte implantation (ACI) - In this procedure, cartilage cells are harvested from your knee, cultured and then re-implanted in the knee to regenerate. This procedure is not appropriate for all patients.

Because the knee is so important, you need to discuss the advantages and disadvantages of any surgical procedure with your doctor. It is also essential that following any surgery, you follow all instructions, including exercise and rehabilitation directions. (Read about "Rehabilitation") The bottom line, according to APTA, is that you are the most significant person in the healing and prevention process. Whatever treatment you receive, the way you treat your knees every day can make a big difference.

Related Information:

    Avoid Sports Injury

    Stretching and Health

    Fighting Weight Gain

    Bone Fractures

    Skeletal System

    The Shoulder