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Torn ACL (cont.)

Knee Anatomy

The knee is a hinge joint where the femur or thighbone connects to the tibia or shinbone. The quadriceps muscles in the front of the thigh and the hamstrings in back have some role in stabilizing the knee, but stabilization is primarily from ligaments. There are four ligaments that keep the knee moving properly. The medial and lateral collateral ligaments keep the knee from shifting side to side, while the anterior and posterior cruciate ligaments keep the knee from sliding front to back.

The anterior cruciate ligament (ACL) is the most commonly injured knee ligament. The ACL attaches the lateral femoral condyle to the tibia just in front of the anterior tibial spine. Some of its fibers also blend into the lateral meniscus. There are actually two bundles of fibers that make up the ligament and allow it to help stabilize the knee in flexion (bending), extension (straightening), and rotation.

Picture of the anatomy of the knee
Picture of the anatomy of the knee

Injured ligaments are called sprains, and they can be classified based upon their severity. A grade 1 a sprain occurs when ligament fibers are stretched but not torn. Grade 2 sprains have some fibers torn, but the ligament remains intact. A grade 3 sprain occurs when the ligament is completely torn.

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