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.
- 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 injured ligament in the knee complex.
- Collateral ligaments are outside the knee joint and prevent medial (inside) and lateral (outside) instability. Ligaments here are injured with a varus stress the LCL (inside to outside force) or valgus stress the MCL (outside to inside force)
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. Depending on the ligament injury – these grades typically require surgery to remedy.
Symptoms can vary but the major symptoms include pain, swelling, and instability. Some can even feel a tear or pop in the knee when injury occurs.
Diagnosis will be determined through a thorough history and physical examination by a trained sports medicine and orthopedic knee specialist. Examination will consist of palpating the knee complex for pain and a visual examination for deformities. T