Knee Sprain: ACL injury
Anatomy of your ACL
Your anterior cruciate ligament (ACL) is inside your knee joint. It attaches from the inside back of your thigh bone (femur) to your shin bone (tibia) closer to the front. Your ACL is one of the main restraints against your tibia being pulled forward and is reinforced by your hamstring muscles at the back of your knee.
How ACL injuries happen
ACL injuries are a common sports injury with approximately 80 - 250 thousand occurring per year based on US studies. 50% of ACL injuries occur between 15 to 25 years of age. You can injure this ligament in either a contact or non contact play.
When contact is involved, you can injure your ACL is commonly when a force is applied to the outside of the knee when your foot is planted on the ground. This type of injury can also result in tears to your medial collateral ligament (MCL) and medial meniscus. This group of injuries is often known as a triad.
You can also injure your ACL in a non contact play. This most commonly occurs with rapid deceleration. This can happen when you abruptly stop to evade another player, if your knee hyperextends or if you twist while your foot is planted on the ground.
Signs of an ACL injury
One of the defining features of an ACL injury is the presence of immediate swelling and knee pain. You may have also heard a popping sound. Rarely will you be able to continue playing. A chronically injured ACL injury will make your knee feel unstable with day to day activities.
Confirmation of an ACL injury
An ACL injury can be confirmed by a proper clinical examination by a physiotherapist with experience in treating sports injuries. This includes a detailed history including how your injury happened. Clinical examination will often include specific ligament testing including the lachman test. This non painful test indicates the looseness of your ACL. Positive findings with the test, when performed properly, correlate with ACL injury. Research has shown that when performed appropriately, clinical examination of an ACL injury is as accurate as MRI in diagnosing ACL tears. Your physiotherapist should also perform additional hands on tests to rule out other similar injures such as meniscal injuries, MCL injuries and patellar dislocation.
Treatment for your ACL injury
Your initial goal post injury should be reducing stress on your injured knee and reducing swelling. Using crutches can reduce pain with day to day activities and allow you to be more functional. Ice can help to reduce swelling and pain and should be used in early stages of your injury. Your physiotherapist will confirm the injury but should also investigate factors that may have led to injury including stiffness in your back and poor range of motion (ROM) and hip muscle control.
Progressive strengthening of your hamstring muscles, secondary stabilizers for your ACL, is crucial to improving your function and stability on your ACL deficient knee. Exercises will start by improving the strength of the muscles in isolation but should progress towards functional, sport specific and proprioception retraining.
We've discussed bracing for knee pain in a previous article. An ACL brace uses special strapping to replicate the stability that your ACL gives. This will give you more stability and help to reduce your pain. Our physiotherapists are trained in the proper measurement and fitting for your ACL brace.
Will I need surgery to repair my ACL?
Whether you need surgery or not will depend on a number of factors. These often include how stable your knee is, if any other structures were injured, how active or sedentary you are and how you're doing with conservative management.