The knee ligaments are bands of tissue that connect your thigh bone in your upper leg (femur) to your lower leg bones (tibia and fibula).

An injury to a knee ligament is called a sprain or a tear. Many knee sprains are mild, but torn knee ligaments can be severe.

Knee ligament injuries are common, especially in athletes. The ligaments can be overstretched or torn when:

• Force is applied to the back of the knee when the joint is partly flexed.

• Force is applied to the front of a bent knee (sometimes called “dashboard injury” because it’s common in car accidents).

• Force is applied to the side of the knee when the foot is on the ground (for example, during a tackle).

• The knee is hyperextended (straightens too much), usually by force.

• The knee joint twists in an unnatural way (for example, when playing basketball or skiing).

f you seek medical attention for a knee injury, a healthcare provider may:

• Ask you about your symptoms and when they started.

• Conduct a physical exam by looking at the injured knee, assessing how it moves and comparing it to the other knee.

• Order imaging tests if necessary, such as MRI, to take pictures of the knee ligaments.

• Take X-rays to rule out a broken leg bone, kneecap (patella) or other problem.

Damage to a knee ligament can weaken the knee joint, increasing the chances that you’ll injure yourself again.

Talk to a healthcare provider if you have:

• Looseness or weakness in the knee.

• Loss of feeling in the knee or leg.

• Pain on the inside or outside of the knee.

• A popping or snapping noise.

• Repeat knee injuries.

• Swelling around the knee joint.

• Trouble putting weight on that leg.