The knee joint is made up of four ligaments, each with their own particular function and characteristics:
- The medial collateral ligament (MCL) sits on the inner part of the knee. It runs from the outer knee joint and joins the thigh bone and the shin bone, on the inside of the knee. It shields the knee from any blows coming toward the outer side of the knee, secures the inner knee, and prohibits the joint from moving too much from side-to-side.
- The lateral collateral ligament (LCL) stretches from the thigh bone to the fibula on the outer surface of the knee joint. It secures the outer knee, and limits hazardous sideways movement.
- The anterior cruciate ligament (ACL) is the most often injured knee ligament. It’s particularly susceptible to sudden twisting movements, typically associated with sports like basketball, hockey and football. The ACL moves across the heart of the knee, connecting the front of the tibia to the back of the thigh bone. The ACL manages rotation and flexion of the knee and stabilizes the shin bone.
- The posterior cruciate ligament (PCL) is situated on the inner knee joint and directs backward motion of the tibia. The PCL runs diagonally across the knee where it intersects the ACL and joins the back of the shin bone to the front of the thigh bone.
The symptoms one experiences the moment a knee ligament is torn will generally be similar, irrespective of which ligament was damaged. The gravity of the injury usually determines the severity of symptoms. Individuals might suffer increased, intense symptoms from a fully torn ligament, and fewer, less harsh symptoms from a stretched or strained ligament.
The instant the ligament is injured, patients may hear a popping noise in the knee, accompanied by immediate and extreme pain. Bleeding in the knee may cause it to swell up; and a tender and bruised knee with diminished mobility is not uncommon.
The knee may have a loose feeling to it, and may not be able to support the weight it usually does, and individuals may even have severe discomfort placing any weight on the knee at all. It may feel insecure when walking, causing some people to limp.
Patients may also experience minor pain on one side of the knee, with no associated swelling or other symptoms. Normal, low impact movements can also trigger periodic inflammation in the joint that may or may not disappear over time.
Partial or full rupture of the knee ligaments can stem from direct impacts to the knee, particularly those from contact sports, and can even be caused from bumping into something at the office or at home.
However, the knee ligaments are more susceptible to being twisted and overstretched when the joint surpasses its mobility limit. Ligaments will then rupture after the knee gets overloaded from one direction, as it tries to secure the joint in place by countering that force.
ACL tears and other knee ligament injuries can stem from:
- Twists in the knee with the foot planted
- Impacts to the knee
- Overextending the knee
- Jumping and landing on a bent knee
- Suddenly stopping when running
- A sudden shift in weight from one leg to the other
These types of injuries occur rather frequently in sports and activities like soccer, football, basketball, skiing, dance and gymnastics.