Pain Profile: ACL Sprain
The knee takes a lot stress from the body due to running, squatting, lunging, and jumping. While running and walking a person’s knee can bear loads of three to four times their bodyweight (Anderson and Parr, 2009, p.574). The knee is also subject to a lot of torque forces because of its position between 2 long bones, the femur and the tibia. The anterior cruciate ligament is a critical stabilizing ligament inside the knee joint that is prone to injury.
The knee is made up of the tibiofemoral joint. Within the tibiofemoral joint there are several structures:
Menisci – disks of fibrocartilage that are attached to the superior plateau (top) of the tibia. Within the tibiofemoral joint there are 2 menisci: the medial meniscus and the lateral meniscus. The functions of the menisci include absorption and dissipation of forces, increases knee stability, and improve the congruency of the joint surfaces to evenly distribute the stress across the joint (Anderson and Parr, 2009, p.575).
Anterior Cruciate Ligament (ACL) – a stabilizer in the knee that prevents anterior translation (forward movement) of the tibia while the femur is stationary, posterior translation (backward movement) of the femur on a stationary tibia, internal and external rotation (twisting) of the tibia on the femur, and hyperextension of the tibia. The ACL is frequently injured during deceleration movements such as changing directions, planting, and cutting (Anderson and Parr, 2009, p.579).
Posterior Cruciate Ligament (PCL) – the primary stabilizer that is shorter and stronger than the ACL. The PCL prevents posterior displacement (backward movement) of the tibia on a stationary femur (Anderson and Parr, 2009, p.580).
Medial Collateral Ligament (MCL) – a ligament that runs across the medial (inside) aspect of the knee to prevent valgus forces (forces hitting the knee from outside). The MCL is more commonly injured over the LCL.
Lateral Collateral Ligament (LCL) – a ligament that runs across the lateral (outside) aspect of the knee to prevent varus forces (forces hitting the knee from the inside).
Types of ACL Sprains
A sprain is an injury to a ligament in the body where a strain is an injury to a muscle. When classifying an ACL sprain, there are three different degrees (Anderson and Parr, 2009, p.142):