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. Because the knee joint relies just on these ligaments and surrounding muscles for stability, it is easily injured. Any direct contact to the knee or hard muscle contraction — such as changing direction rapidly while running — can injure a knee ligament.
Collateral Ligaments These are found on the sides of your knee. The medial collateral ligament is on the inside and the lateral collateral ligament is on the outside. They control the sideways motion of your knee and brace it against unusual movement.
Cruciate Ligaments These are found inside your knee joint. They cross each other to form an “X” with the anterior cruciate ligament in front and the posterior cruciate ligament in back. The cruciate ligaments control the back and forth motion of your knee.
The anterior cruciate ligament runs diagonally in the middle of the knee. It prevents the tibia from sliding out in front of the femur, as well as provides rotational stability to the knee.
Injuries to the collateral ligaments are usually caused by a force that pushes the knee sideways. These are often contact injuries, but not always. Medial collateral ligament tears often occur as a result of a direct blow to the outside of the knee. This pushes the knee inwards (toward the other knee).
SYMPTOMS OF LIGAMENT DAMAGE
Symptoms of an ligament injury include hearing a sudden popping sound, swelling, and instability of the knee (i.e., a “wobbly” feeling). Pain is also a major symptom in an ACL injury and can range from moderate to severe. Continued athletic activity on a knee with an ACL injury can have devastating consequences, resulting in massive cartilage damage, leading to an increased risk of developing osteoarthritis later in life.