The anterior cruciate ligament, ( ACL), is probably the most infamous ligament in the knee when it comes to sports or activity related injuries. We are probably most aware of these injuries in professional footballers, netball players or basketball players who undergo knee reconstruction after an injury on the field of play.
However us mere mortals are also vulnerable to this type of injury from something as innocuous as getting our foot caught while pivoting, or accidently getting bumped by a marauding toddler.
Unfortunately in Australia we lead the way in ACL injuries sustained in both adults and children. This is a reflection on the popular sports we play and surfaces we play on.
What is the ACL and what does it do ?
The ACL is a major internal ligament that crosses from the front of the tibia to the back of the femur. It has a partner called the posterior cruciate that goes from the front of the femur to the back of the tibia.
The ACL performs the following functions in the knee:
- Prevents forward movement/ anterior translation of the tibia on the femur.
- Prevents external rotation of the tibia on the femur.
- Helps with joint position sense of the knee, thus improving our movement patterns and balance.
How do we injure the ACL ?
Usually the ACL is injured through;
- Collision with another player or individual
- Changing direction / cutting suddenly when running. Think of the side stepping footballer.
- Landing badly on one leg from a jump. netballers and basketballers beware.
- Having the foot fixed on the ground as the body twists over the top of it.
Mechanically the common mechanism is the knee goes into valgus with increased external rotation at the tibia.
Here is a clever little animation that shows us nicely what occurs in a cutting type movement and is made worse with an external collision force.
What happens when we injure our ACL.
When you injure your ACL, you may hear a “pop” at the time of injury coupled with buckling of the knee. There is usually immediate pain and swelling.
The pain may resolve, but the knee may remain unstable and there is sometimes a loss of motion. This may due to the knee being angry , inflamed and swollen. there can also be a mechanical block caused by the stumps of the torn ACL preventing normal movement.
With ACL injuries it is not uncommon that there may be other tissues injured alongside this ligament. Probably the most common that co exist are meniscus tears , bony bruising and medial collateral ligament issues.
What should i do if i have just suffered an ACL injury ?
GET IT ASSESSED.
The first things you need to do are apply the rice principles to the acute injury and seek assessment to ascertain the extent of the injury. The happier we can get the knee then the quicker we can get on to the appropriate treatment path.
There are certain tests we can do that can identify if the ACL is potentially ruptured. If they come up positive then an MRI is the best way to get confirmation of the diagnosis.
In the MRI the red arrow points to a thick black band which is a healthy intact ACL.
The knee on the right has less defined irregular mass where the ACL should be. That is what a torn ACL often looks like on a scan.
Acute ACL Tear
The first goal with all injuries is GET A QUIET OR HAPPY KNEE ASAP
The initial goal is to get the knee back to its “happy place”. By that we mean we want to reduce the swelling and pain , restore movement and keep the knee functioning as well as possible.
This usually involves a combination of the RICE/ PEACE & LOVE principles as well as the introduction of basic quads and hamstring exercises.
This video is a great resource for early stage knee exercises.
We want to keep the muscles as active as possible and prevent any secondary weakness or atrophy.
Kanon ACL Post operative rehabilitation protocol
These exercises are based on the Kanon trial for post operative ACL or acute knee injury rehabilitation. They are an example of the first 4-6 weeks of rehab from this trial which showed very positive results with knee function after following this protocol.
Based on the Kanon ACL rehabilitation protocol
ACL Exercises phase 1 : Day 1-14
- Knee flexion / hip extension
- Inner range quads
- Sit to stand
3-5 sets x 12-15 reps
ACL Exercises phase 2 week 2-4
- Knee slides
- Norwegian push ups
- Step downs
- Lateral step downs.
This is the starting point for your rehabilitation of your knee injury. It applies to ACL ruptures as well as acute knee ligament injuries. In our next blog we will have a look at how to ace your pre-hab and rehab and how a 5 week intensive rehab program can be a game changer before surgery.
If you have had knee injury or ACL reconstruction and are needing help with rehab and getting back to sport you can book in to see one of us and ace your rehab here:
Eitzen, I., Moksnes, H., Snyder-Mackler, L., & Risberg, M. A. (2010). A progressive 5-week exercise therapy program leads to significant improvement in knee function early after anterior cruciate ligament injury. J Orthop Sports Phys Ther, 40(11), 705-721. doi:10.2519/jospt.2010.3345
Hurd, W. J., Axe, M. J., & Snyder-Mackler, L. (2008). A 10-year prospective trial of a patient management algorithm and screening examination for highly active individuals with anterior cruciate ligament injury: Part 1, outcomes. Am J Sports Med, 36(1), 40-47. doi:10.1177/0363546507308190