The knee is a joint that joins the thigh bone (femur) to the top of the shin bone (tibia). It is made up of bones, cartilage , muscles, ligaments , and tendons. These parts work together to make the legs bend, straighten, and swivel. A knee injury can damage one or more parts of the knee.

Anatomy of the knee

What Causes Knee Injuries?

Teens may injure a knee in a fall or accident. Active and athletic teens might have overuse knee injuries. These happen when someone trains too much or makes repetitive motions involving the knee.

Common knee injuries in teens include:

  • sprains: when a ligament stretches or tears; for example, an anterior cruciate ligament (ACL) or medial collateral ligament (MCL) tear
  • strains: when a muscle or tendon tears part or all of the way
  • tendonitis: when a tendon gets irritated or inflamed, usually from overuse or poor training (for example, in jumper's knee
  • meniscal tears: when the cartilage between the upper and lower leg bones (the menisci) tears
  • fractures: when a bone breaks
  • dislocation of the patella (kneecap): when the kneecap slides out of place
  • Osgood-Schlatter disease: inflammation of the tendon that attaches the kneecap to the shinbone
  • Osteochondritis dissecans: when a small piece of bone in the knee loses blood supply and breaks off
  • bursitis: swelling of one of the fluid filled sacs that cushion the knee.

What Are the Signs & Symptoms of a Knee Injury?

The signs and symptoms of a knee injury depend on the cause. Most knee injuries cause pain. A knee injury may also lead to the knee feeling weak, "giving way," or "locking." Someone with a knee injury might not be able to fully bend or straighten the knee. The injured knee may be swollen or bruised.

How Are Knee Injuries Diagnosed?

To diagnose a knee injury, health care providers ask about how the injury happened and what symptoms it causes.

The health care provider will do a physical exam that includes pressing on the knee and legs and moving them in certain ways. These tests can show what part of the knee is injured.

Imaging tests done sometimes used include:

  • X-rays to check for injuries to the bones
  • a CT scan or MRI to look inside the knee

How Are Knee Injuries Treated?

Treatment for a knee injury depends on the cause. Some knee injuries just need RICE:

  • Rest
  • Ice
  • Compression (with an elastic bandage)
  • Elevation (raising the injured knee)

Other knee injuries may need bracing, physical therapy, or even surgery.

Can Knee Injuries Be Prevented?

To help prevent knee injuries:

  • Be sure you wear the recommended protective equipment for sports (such as knee pads and shin guards).
  • Wear supportive athletic shoes that are in good condition.
  • During workouts, always warm up and cool down.
  • Do regular strength training to support muscles, and stretching or yoga to improve flexibility.
  • When jumping, bend the knees while landing. This takes pressure off the ACL and prevents injury.
  • If you cut laterally or pivot frequently (as in soccer), crouch and bend at the knees and hips to reduce the chances of an ACL injury.
  • If you play just one sport, conditioning and training year-round — even if it's at a lower intensity than during the competitive season — can help you stay in shape and make an injury less likely.

What Else Should I Know?

If your knee hurts, it is important to know why. Go to a health care provider to find out what's causing the pain and to get treatment.

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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2020 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.

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