This is a stretching or tearing of a ligament on the inner side of your knee. The medial collateral ligament, commonly called the "MCL", is connected to the femur and to the tibia. The MCL helps stabilize your knee. This ligament, along with the lateral collateral ligament, helps prevent excessive side-to-side movement of your knee joint. It helps keep the upper and lower leg aligned properly.
You can injure your MCL when your knee is pushed sideways toward the inner side of your body. A hard blow to the outer side of your knee is a common culprit. With a mild injury, your MCL may only stretch. Some of its fibers may tear. But if your injury is severe, your MCL may rupture completely.
An MCL injury causes pain and swelling of the inner side of your knee. Your knee may feel stiff. It may feel unstable and weak. It may lock or catch when you walk. Some people experience numbness or weakness in the foot after an MCL injury.
Many MCL injuries can be treated with rest, ice and physical therapy. You may benefit from a knee brace. If these are not helpful, you may benefit from surgery to repair the damage. Your healthcare provider can develop a care plan that is right for your needs.