Your MCL also connects your femur to your tibia, but this ligament runs along the inside of your joint. An outside blow to the knee tears the MCL much like a strap stretched too far: it snaps.

Impact injury to MCLAn impact injury

When your knee is struck from the outside, it’s stretched beyond its normal range of motion, which can cause the MCL to tear. If your MCL snaps you might hear or feel a pop and your knee may buckle sideways. Pain and swelling are common and either a complete or partial tear is possible. It’s not unusual to tear the meniscus or ACL at the same time.

After MCL injury, your knee more easily buckles sideways.

After MCL injury

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