According to William Prentice, the author of "Arnheim's Principles of Athletic Training," the knee is one of the most complex joints in the human body. The knee is also the joint most likely injured due to the stress that certain sports and recreational exercises place on the knee. The bones, menisci, and ligaments of the knee are designed to provide stability to the lower leg during locomotion. Hyperextension of the knee joint often results in damage to the posterior cruciate ligament.
Posterior Cruciate Ligament
The posterior cruciate ligament, or PCL, remains taut throughout full range of motion of the knee. It acts as a drag during the gliding phase of movement and it also resists internal tibial rotation. The main job of the PCL is to prevent hyperextension of the knee and femur. Damage to the PCL leads to instability of the knee with the tendency of the shin bone to lag backward when bent to 90 degrees.
Mechanism of Injury
Injury to the PCL is less common than injury to the anterior cruciate ligament and the medial collateral ligament. Damage to the PCL is caused most often by a direct hit to the tibia causing hyperextension while the knee is bent. When the PCL is injured, other structures of the rear compartment, such as the lateral meniscus, are also injured.
Identification
When knee injury occurs, a qualified health professional will perform tests on all the ligaments and menisci of the knee to determine where the damage is. The specific tests used to determine PCL injury related to knee hyperextension are the sag test and the posterior drawer. Both tests are designed to detect laxity in the tibia, which is an indication of PCL damage.
Rehabilitation
If hyperextension of the knee and damage to the PCL occur, the plan of action is to control pain and swelling by taking NSAIDs. Immobilizing the knee is the next priority, followed by working on range-of-motion exercises. As strength improves, swelling subsides, and pain decreases, a program of strength training can begin. The strength training focus is placed on the quadriceps muscle, because the quadriceps initiate an anterior pull on the tibia and remove stress from the PCL.
Injury Prevention
To prevent injury to the knee, engage in a regular program of strength training. The strength training program should focus on all the muscles that surround the knee joint including the quadriceps, hamstrings, calves, and anterior tibialis muscles. Warm up all the muscles of the body before activity by performing low to moderate intensity cardiovascular exercise. Use proper techniques for sport and recreational exercise and train at an intensity appropriate for your fitness level.
References
- "Arnehim's Principles of Athletic Training 12th edition"; William Prentice; 2008
- PCL Injuries
