When you read about sports injuries, knee problems are always near the top of the list. Your knee joint is somewhat like a hinge and works nicely in a vertical plane. Unfortunately, it is very unforgiving if it's forced to move sideways or is twisted.

There are several causes of knee problems. Impact injuries are often due to direct blows in contact sports like basketball. They can also be caused by falls and jumps, sudden twisting, and explosive movements such as a power lift.

Overuse injuries happen if you overtrain and can be associated with anatomical variation (something that doesn't quite match the textbook pictures) either in your knee itself, or transmitted up your leg from your foot or down from your hip.

Basic Structure

Ligaments join your thigh bone (femur) to the leg bones (tibia and fibula). Cruciate ligaments cross each other on the inside. On the outside of the joint you'll find collateral ligaments. Ligaments are tough, fibrous bundles which are strong but only slightly elastic.

Two C-shaped disks of cartilage (menisci) sit on top of the tibia, the large leg bone, and act as shock absorbers. There's a thin coating called articular cartilage on the end of the femur and tibia that's in contact with the menisci. As well as absorbing shock, cartilage prevents wear because it reduces friction.

Your kneecap protects the front of the joint. When your knee flexes the kneecap glides in a groove in the femur.

Tendons join muscles to bones, and also help to hold your kneecap in position. The muscle group of your front thigh is the quadriceps group, and its tendons attach to your kneecap and tibia. Hamstring tendons attach the back thigh muscles to your tibia. Calf muscles tendons connect to the tibia, and femur. There is also a band at the outside of your knee. This is a narrow stabilizing (rather than load bearing) muscle-tendon structure which runs from your tibia to your hip.

Tendon Injuries

Tendinitis is a common overuse injury. Overwork causes inflammation. Runners may develop pain at the back of their knees (usually hamstring tendons), and at the outside of their knees (iliotibial band syndrome). A lot of jumping can cause pain below the kneecap (jumper's knee). Tendon pain is usually worse when you get out of bed, and slowly eases off with use. Resist using this to persuade yourself you can exercise as usual.

Tendinitis can be persistent because tendons don't have such a good blood supply as muscles. Since it's usually caused by overuse, the most important part of the treatment is rest. This may not mean inactivity, but it certainly means a reduced workload. The best approach is to alter your workout to rest the tendon but retain fitness. In addition, heat the area before exercise to help the blood flow, and ice it after exercise to reduce inflammation.

Aspirin and ibuprofen can be useful anti-inflammatory drugs, but only if you rest. Never use medication to mask pain so that you can continue to work out. This will make the problem worse. Then it may become chronic, and can have serious consequences. Tendinitis is more likely if you have tight muscles, so stretching usually helps to keep you out of trouble.

Cartilage Injuries

Most cartilage injuries are due to impact or twisting movements, and are more common in contact sports. Anyone can fall, though, including runners and cyclists. Blows and falls can cause cartilage tears. These can hurt, cause clicking noises, and may make your knee lock on occasions. Cartilage can also become damaged by accumulated repeated wear and tear, says American Running Editorial Board Member Marvin Bloom, M.D.

Small tears in a meniscus may heal with rest. Menisci have a variable blood supply, and in some cases healing can take months. Larger tears and complete tears are more difficult.

Cartilage injuries need expert care. In many cases, a conservative approach with rest and a change of activity works well. The change may have to be permanent, though. Putting stress on a damaged cartilage can only lead to more problems.

If surgery is needed, procedures vary. Some tears can be stitched together and will then heal. Others may need fragments removed. A very badly damaged cartilage may have to be removed completely. Arthroscopic surgery involves small instruments and an optical system inserted in your knee. You'll usually recover relatively quickly, and begin rehabilitation.

The worst part of cartilage injuries is the ogre of arthritis. A damaged meniscus can grind on articular cartilage, and damage it. The surfaces roughen, pieces may break off, and wear and tear accelerates. The whole area becomes inflamed and swollen, and the problem grows. The risk of arthritis seems to be higher after surgery, but perhaps that really reflects the severity of the damage in the first place.

Ligament Injuries

Ligaments are more likely to suffer impact injuries than overuse injuries. Knee ligament damage has hampered or ended many football, basketball, and hockey careers. Falls and accidents can also damage ligaments.

Ligament tears are called sprains. If the ligament is just stretched or slightly torn, it should heal with RICE: rest, ice, compression (brace), and elevation.

As the severity of a tear increases, the likelihood of instability increases. Surgical repair may be the best treatment for complete rupture or a bad tear.

Violent muscle contractions also cause knee injuries, says American Running Editorial Board Member Mitchell Goldflies, M.D. If you land from a jump with your knee extended, your quadriceps muscles can contract violently enough to rupture the anterior cruciate ligament, he explains.

Collateral ligaments reinforce your knee on the outside and help stabilize it. The internal cruciate ligaments hold your knee together. Torn anterior cruciate ligaments pose the biggest threat to knee stability, but damage to any knee structure puts more stress on the other tissues.

Damaged knee ligaments need early diagnosis and treatment. Even so, healing and rehabilitation often take a long time. Under the guidance of an experienced physical therapist, rehabilitation commonly takes six to nine months, and sometimes a year or more may be needed. Since ligament tears are commonly caused by violent blows and movements, they are often accompanied by cartilage damage.

Runner's Knee

Running can cause pain at or near your kneecap. It will usually be obvious that it's an overuse injury because it will come on slowly, or after a greater than usual effort. It will probably go away when you stop running, and return when you start again. The problem is inflammation of cartilage under your kneecap. In some cases biomechanical problems in your feet cause abnormal movement in your kneecap. In these cases RICE (and perhaps aspirin or ibuprofen) will treat the symptoms, and orthotic inserts in your shoes can treat the cause.

Sometimes pain under your kneecap is due to abnormal tracking of your kneecap in its groove which is often caused by imbalances in the muscles around the knee.

Strategy for Knee Injuries

If you develop a sore area in your knee which is obviously an overuse injury, you should manage quite well with RICE. Take aspirin or ibuprofen as well, and you should see significant progress in a week or two. If there's no marked improvement after two weeks, seek professional help. If you cure your symptoms, but they return soon after you resume your workout, you need help to track down the cause.

After trauma to your knee, if you sense a mild sprain begin RICE treatment. After two or three days you should feel some improvement. If not, get help.

If you took a heavy blow or fell and you heard a popping noise, or if your knee is unstable and won't bear your weight, or if it clicks or locks, go immediately to a sportsmedicine orthopedist. This has the potential to be a serious problem and you shouldn't fool with it.

Prevention of Knee Injuries

The greatest factor which can protect your knees is sound training. Hard days must be followed by easy days and hard weeks by easy weeks. If you compete, train to peak not more than twice a year, and don't try to prolong your peak for much more than a couple of weeks. It's okay to compete regularly, as long as you build it into your training program and don't go all out every week. Avoid increasing the length or intensity of any kind of workout by more than 10% in a week. Rest and recovery are the keys to your training; that's when your body grows stronger.

Even if you have sound knees, you can help them. Strengthening your leg muscles will reduce the load on your knee joint. Stretching will reduce the load on your tendons. Together, these precautions are good insurance against knee injuries, and are especially valuable if you compete regularly.

Copyright, The American Running Association.

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