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. What Causes Knee Injuries? Kids and teens may injure a knee in a fall or accident. Active and athletic kids might have overuse knee injuries. These happen when someone trains too much or makes repetitive motions involving the knee. Common knee injuries in kids and 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: Make sure your kids wear the recommended protective equipment for sports (such as knee pads and shin guards). Make sure your kids wear supportive athletic shoes that are in good condition. During workouts, kids should always warm up and cool down. Encourage kids to do regular strength training to support muscles, and stretching or yoga to improve flexibility. When jumping, kids should bend the knees while landing. This takes pressure off the ACL and prevents injury. If kids cut laterally or pivot frequently (as in soccer), encourage them to crouch and bend at the knees and hips to reduce the chances of an ACL injury. For kids who play just one sport, conditioning and training year-round — even if it's at a lower intensity than during the competitive season — can help them stay in shape and make an injury less likely. What Else Should I Know? If your child's knee hurts, it is important to know why. Take your child to a health care provider to find out what's causing the pain and to get treatment. Back to Articles Related Articles Medial Collateral Ligament (MCL) Injuries MCL injuries can happen in active and athletic kids, when excessive pressure is put on the knee joint, resulting in a torn ligament. Read More Patellofemoral Pain Syndrome (Runner's Knee) Patellofemoral pain syndrome (or runner's knee) is the most common overuse injury among runners, but it can also happen to other athletes who do activities that require a lot of knee bending. Read More Jumper's Knee Jumper's knee is an overuse injury that happens when frequent jumping, running, and changing direction damages the patellar tendon. Read More Jumper's Knee Jumper's knee is an overuse injury that happens when frequent jumping, running, and changing direction damages the patellar tendon. Read More Bursitis Bursitis, an irritation of the small fluid sacs that provide cushioning in some joints, is often caused by sports-related injuries or repeated use of a particular joint. Read More Knee Injury: Caroline's Story Caroline loved sports. But when an ongoing knee injury kept her from playing the sports she loved, she discovered new interests. Read her story. Read More Knee Injuries Healthy knees are needed for many activities and sports and getting hurt can mean some time sitting on the sidelines. Read More Medial Collateral Ligament (MCL) Injuries MCL injuries happen when excessive pressure is put on the knee joint, causing a torn ligament. Read More Overuse Injuries Overuse (or repetitive stress) injuries happen when too much stress is placed on a part of the body, causing problems like swelling, pain, muscle strain, and tissue damage. Read More Sports and Exercise Safety Playing hard doesn't have to mean getting hurt. The best way to ensure a long and injury-free athletic career is to play it safe from the start. Find out how. Read More Preventing Children's Sports Injuries Participation in sports can teach kids sportsmanship and discipline. But sports also carry the potential for injury. Here's how to protect your kids. Read More Osgood-Schlatter Disease Osgood-Schlatter disease (OSD) is an overuse injury that can cause knee pain in teens, especially during growth spurts. Learn more. Read More Bones, Muscles, and Joints Without bones, muscles, and joints, we couldn't stand, walk, run, or even sit. The musculoskeletal system supports our bodies, protects our organs from injury, and enables movement. Read More Osgood-Schlatter Disease Osgood-Schlatter disease (OSD) is one of the most common causes of knee pain in adolescents. It's really not a disease, but an overuse injury. Read More Your Bones Where would you be without your bones? Learn more about the skeletal system in this article for kids. Read More Anterior Cruciate Ligament (ACL) Tears ACL injuries can happen in active and athletic kids when excessive pressure is put on the knee joint, resulting in a torn ligament. Read More Anterior Cruciate Ligament (ACL) Tears ACL injuries can happen in active and athletic kids when excessive pressure is put on the knee joint, resulting in a torn ligament. Read More Meniscus Tears The key to healing meniscus tears is not to get back into play too quickly. Find out what meniscus tears are and how to treat them. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.