The hinge-like movement of your knee is supported by a network of bones, muscles, ligaments, and tendons. But these tissues can cause knee pain if they are overused, become inflamed, or are subject to a blow or other injury. Each element of the knee is susceptible to some common sports injuries. Many of the symptoms for knee injuries are similar, which is why the diagnosis of a doctor or sports specialist is important to say definitely what’s causing your knee pain. But if you know the main causes of knee pain—and the occasional distinctive symptoms—you’re closer to the diagnosis and treatment you need.

Bone or kneecap injuries

Bone dislocation can occur if the femur (thigh bone) or tibia (shin bone) get out of alignment, or if the patella (kneecap) slips out of place. The patella can also be fractured. These are almost always as a result of severe trauma, such as a fall or car accident. Both patellar fractures and dislocations cause knee pain, but the pattern is slightly different: For a dislocation, the pain will be sharp but fade with rest. Patellar fractures, on the other hand, tend to cause sharp pain immediately after injury, then remain consistently aching throughout healing.

Ligament injuries

The anterior cruciate ligament (ACL) crisscrosses with one other ligament in the knee. It keeps the knee aligned and prevents it from slipping forward or backward. However, it’s prone to rips or tears, particularly when the knee twists sideways. An ACL tear is a common sports injury, and women are more prone to it.

ACL injuries almost always occur after a sudden blow or pivot. They can also occur when the knee is hyperextended. People hear a “pop,” then experience pain and a feeling of the knee “giving out” from under them.