Three bones meet to form your knee joint: your thigh bone (femur), shinbone (tibia), and kneecap (patella). Your kneecap sits in front of the joint to provide some protection. Bones are connected to other bones by ligaments. There are four primary ligaments in your knee. They act like strong ropes to hold the bones together and keep your knee stable.
An ACL (anterior cruciate ligament) injury is one of the most common and well-known orthopedic injuries. The ACL is a very important ligament because it prevents the tibia (shin bone) from sliding in front of the femur (thigh bone). The ACL stabilizes the knee while walking, running, jumping, and moving from side to side. The posterior collateral ligament is within the knee and prevents the femur from sliding off the anterior edge of the tibia and to prevent the tibia from displacing posterior (similar to the anterior cruciate ligament ) and is not as commonly injured.
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