If you collide with another player when you’re playing a sport and the side of your knee is hit hard, your MCL may be injured. The MCL (medial collateral ligament) is a band of tissue that runs along the inner edge of your knee. It helps to connect your shin and thigh bones to keep your knee stable and working properly when you move.
When your MCL is damaged, your knee can over-extend itself, or bend too far in a direction that it’s not supposed to bend. You may heal on your own with basic care, rest, and rehab. But if your injury is severe, you may need to have surgery.
When your outer knee is hit very hard, the MCL, which runs along your inner knee, can stretch out far enough to strain or tear. People who play football, hockey, and other sports where players impact other athletes with great force may injure their MCL this way.
You may also stretch or tear your MCL if your knee is suddenly pushed to the side, or if it twists or bends out too far.
MCL injuries hurt. Most people feel pain along the inside edge of the knee, and they also have swelling. You might hear a pop when the damage to the knee takes place, and your knee may lurch to the side.
You may find it hard to walk, or feel like you can’t put pressure on the leg with the hurt knee. You might feel like you are going to fall because your knee isn’t stable enough for walking, even if it doesn’t hurt to walk on it.
Some people can walk, but their knee feels loose, and it wobbles more than it should when they move.
Sometimes, the knee may feel stiff, or the joint may lock or catch when you move around.
Your doctor will want to know how you got hurt and how you’ve been feeling and getting around since the injury.
They’ll check to see whether you’ve damaged your MCL and how badly it’s been stretched or torn. They may push on the inside of your knee to see how stable or loose the joint is and whether it hurts. They may also press on the outside of your knee when your leg is both bent and straight to check on how bad the problem is.
Your doctor may also want to do some imaging tests of your knee:
MRI. An MRI study can show MCL damage, so your doctor will know how bad your strain or tear is.
X-ray. It won’t show your MCL, but it can show whether you have a broken bone.
Stress X-ray. Although X-rays show bones and not soft tissues like ligaments, your doctor may be able to tell whether or not your MCL is torn with a stress X-ray. You’ll try to relax, and then your doctor or the person doing the X-ray will gently pull on the MCL side of your knee to see if it opens up farther than it should. If the image shows a bigger gap than there should be between the shin and thigh bones, then the joint is loose, and it’s likely that your MCL is torn.
If you have a mild MCL strain, it can heal on its own with rest, ice, and other self-care. You’ll need to raise your sore knee when you put ice on it, keep weight off the joint, and protect and compress the injury with a knee brace or elastic bandage.
For more severe damage, you may need physical therapy to rehab your knee when your MCL pain begins to fade. Your physical therapist will give you exercises to strengthen the leg muscles around your knee so it works properly.
It’s rare for someone with an MCL injury to need surgery, since this ligament can often heal within a few weeks or months with the help of other measures. But you might need it, especially if another part of your knee is also hurt.
Whether or not you need surgery, you may be able to play sports again with a few weeks or months. Your doctor can let you know when it’s OK to get back to those activities, and they may ask you to wear a knee brace when you’re active.