ACL
Anterior Cruciate Ligament
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Anatomy
The anterior cruciate ligament, ACL, is located in the center of the knee joint and helps to stabilize the knee, especially in internal rotation and with forward forces on the lower leg, typically during sports. It acts as a seatbelt during directional changes and trauma to prevent the knee from going out of its normal position.
Injury
ACL tear is generally a sports injury, either by non-contact change of direction while running or with twisting trauma. When injured, patients commonly refer to a “pop”-sound or a “give-away” of the knee and thereafter swelling and pain. The pain and swelling usually subsides, and the main remaining symptom is instability to the knee, specifically when trying to go back to jumping, twisting or sports.
MRI of normal ACL
MRI of ACL tear
Evaluation
First of all, a detailed history and good physical examination is key to evaluate a knee injury and with the specific tests for ACL, including Lachman test and Pivot shift test, you can diagnose the injury. However, 50% of ACL tears occur in combination with other injuries that can potentially change the treatment, which is why X-rays and MRI are important to evaluate the full scope of the injury.
Positive Lachman Test
Positive Anterior Drawer Test
Treatment
An isolated ACL tear can be treated both non-operatively, with a specific physical therapy program to activate and rebuild muscular control of the knee and the new circumstances without a proper seatbelt. This generally takes about 9 months and can be a good option for patients with lower demands or partial tears.
However, with an unstable knee in a young individual aiming to go back to sports, a surgical treatment, ACL-reconstruction, provides better stability and lowers the risk of other injuries that is common with further give-aways of the knee. After the surgery, a similar physical therapy protocol is used to get back to activities.
ACL Reconstruction
This needs to be individualized!
There are multiple ways of performing an ACL reconstruction, with different techniques, different grafts and different additional procedures.
For graft, the most common ones are Patellar tendon (BTB), hamstring tendons and Quadriceps tendon. They all have their strengths and weaknesses.
Additional procedures are other, usually smaller, procedures that can help make the knee more stable and reduce the risk of problems or even failure of your ACL reconstruction. The most common ones are lateral extra-articular tenodesis (LET) and slope reducing osteotomy (see below).
All factors of the patient are important and adds to what the optimal treatment for her/him is. What age? What sport? First or second injury? How loose is the knee? MRI- and X-ray findings? Other injuries? It all adds up and then the best treatment for that specific individual can be planned.
There is no such thing as the BEST treatment for all, but there is a BEST treatment for you, make sure that is what you are getting!
Image of torn ACL during arthroscopy
Image of reconstructed ACL during surgery
Fixation of ACL graft
Lateral extra-articular tenodesis (LET)
Lateral extraarticular tenodesis (LET) is a surgical procedure to reconstruct the anterolateral ligament complex of the knee. This part of the knee helps to stabilize the knee in rotation and is commonly injured with an ACL tear. This procedure has been shown to reduce failure rates of ACL-reconstructions, especially in young individuals going back to sports or in those with high grade rotational instability after an ACL injury.
It is a small procedure on the lateral side of the knee where part of the Iliotibial band running on the outside of the thigh is re-routed under the LCL and fixed to the bone. It does not change the rehabilitation or recovery time of the ACL reconstruction.
Schematic view of an LET
Posterior Tibial Slope
The tibial slope is basically the tilt of the top of the tibia. The more tilt, the more force is put on your ACL. In the setting of an ACL injury, the posterior tibial slope is measured and the higher it is, the higher risk of failure of ACL reconstruction. If the tibial slope is too large (>12-15 degrees) an additional procedure, called slope reducing osteotomy, is performed together with the ACL reconstruction to make sure you have the best possible chance of success. This osteotomy demands a few weeks of crutches to make sure it heals before you start loading with your full bodyweight, but it does not change the final recovery time.
A: Increased posterior tibial slope
B: Osteotomy to remove a wedge of bone
C: Closing the wedge, flattening the top of the tibia
D: Fixed with a plate
Rehabilitation
With or without surgery, as mentioned, a physical therapy program needs to be completed to be able to use the knee to its potential. To evaluate when your knee is ready to go back to certain activities, strength testing is done and certain thresholds are used to determine if you are ready.
In broad terms, it can be divided into three stages.
0-3 months is recovery after injury/surgery to get back to normal walking, climbing stairs and living a hassle-free everyday life.
4-6 months is about getting back to activities, such as biking, swimming, gym-training and running.
7-10 months is all about preparation for sports. This includes jumping, turning, twisting, sprinting and specific sports-drills to get ready to get back to compete.