The Anterior Cruciate Ligament ACL is sprained or ruptured when the Tibia is forced anteriorly in relation to the Femur. This kind of injury is seen when the knee is forced into Hyperextension. Rotational stresses on the knee when the Femur rotates on a fixed Tibia is still the most common mechanism of ACL tear or rupture.
The Posterior Cruciate Ligament PCL has the opposite function of the ACL as it prevents posterior (backward) translation of the Tibia on the Femur. Injuries of PCL occur when the Tibia is forced posteriorly (backward) on the femur this is commonly seen in “dashboard” injury but it is also seen in forced hyperextension (when the knee is bent backwards) of the knee.
The Medial Collateral ligament MCL is mainly affected when the knee is forced into valgus stress (figure B). This happens when the force is applied on the lateral surface of knee when the Tibia is fixed on the ground as seen in American football and Rugby. MCL sprain could be also associated with medial meniscus injury as the deep fibers of the ligament is attached to the meniscus.
The Lateral Collateral Ligament LCL injuries to the LCL are less common than MCL injuries. however the mechanism of injury requires a varus stress on the knee joint (figure C) with a fixed tibia.
Management of ligament sprain depends on the grade of injury. Ligament sprain can be classified into three groups:
Grade I Ligament Sprain: minimal tear of the ligament associated with slight pain and mild swelling. No functional instability.
Grade II Ligament Tear: more disruption of the ligament fibers. majior pain and swelling associated with joint stiffness and mild-moderate instability of the joint.
Grade III Ligament Sprain (rupture): in this case the integrity of the ligament is lost. Severe Pain and swelling associated with instability of the joint. This grade is an indication for surgery.
Early intervention in the acute stage aims at reducing pain, controlling joint swelling and restoring range of motion of the joint.
The early physiotherapy intervention after such injury follows the PRICE protocol:
Protection: by avoiding weight bearing on the joint or sudden movements by using crutches or immobilizing the joint by using a brace.
Ice application: applied in the first 48 hours for 10 minutes every two hours.
Compression by bandaging the joint which helps in controlling the swelling.
Elevation: raising the lower limb on a high pillow ( above the heart level) helps to push the fluids towards the blood stream by the help of gravity.
After the removal of brace ( which is used between 3-6 weeks depending on the grade of injury), the patient ends up with a stiff joint and tight and weak muscles. Physiotherapy helps the patient to:
- Control swelling if still present.
- Mobilization of the knee joint both (Patellofemoral and Tibiofemoral joints).
- Stretching tight muscles.
- Strengthening weak muscles.
- Optimizing balance.