The knee is the largest and one of the most complex joints in the human body. It consists of 4 bones, multiple ligaments, muscles and tendons, cartilage and soft tissue. Knee ligaments connect bones to bones allowing for stability. Injuries to these ligaments affect more than 12 million people a year requiring visits to orthopedic physicians.
Ligaments of the knee are classified as cruciate and collateral ligaments. Ligaments connect bone to bone. The major ligaments of the knee consist of the ACL (anterior cruciate ligament, PCL (posterior cruciate ligament), MCL (medial collateral ligament) and LCL (lateral collateral ligament). Cruciate ligaments are within the knee joint. They prevent anterior (forward) and posterior (backward) translation of the femur from the tibia.
The ACL is the most commonly injured ligament in the knee complex. Recent studies from 2016 show that nearly 250,000 of these injuries occur per year. Nearly 70% of tears are non-contact injuries – such as a sudden stop, a rapid change of direction or incorrectly landing after jumping. Other studies have shown the female patients have a markedly higher risk of injuring the ligament than male athletes. High-risk sports include gymnastics, skiing, football, basketball, and soccer. Injuries to these ligaments are called tears or sprains. Ligament sprains are classified on a severity scale called grades.
- Grade 1 sprains occur with mild damage to the structure. These injuries continue to keep the joint stable but the ligament is stretched / mildly torn.
- Grade 2 sprains or moderate tears when they occur cause added instability and looseness of the joint. Partial tears at this level may cause episodes or feelings of instability. This grade of injury can be treated without surgery but if typical conservative measures fail then surgery would be recommended.
- Grade 3 sprains or full/complete tears allow for complete joint laxity or no stability. Pending the ligament injury – these grades typically require surgery to remedy.