The knee has four major ligaments, the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the lateral collateral ligament (LCL) and the medial collateral ligament (MCL). The lateral meniscus and medial meniscus act as shock absorbers and gliding surfaces between your femur (thigh bone) and tibia (shin bone).
Right knee, front view
This post aims to cover everything you need to know about your ACL
While among fellow atheletes the seriousness of the dreaded three lettered abbreviation is understood it’s often not fully comprehended, more so with those who have little or no participation in sport.
What’s the function of the ACL?
The ACL is the most important ligament in the knee providing stability to the knee in dynamic movements, such as pivoting, stopping and turning. It consists of two bundles of fibre rooted deep in the femur connecting to two sites on the tibia.
It’s primary function? It stops anterior translation and medial rotation of your tibia in relation to your femur. What does this mean? Without your ACL your shin bone can slide foward and in front of your knee, or when rotating on your foot (rotating to the outside of your leg) your thigh bone will rotate with your hips but your shin bone might not. The knee becomes unstable and dislocation is likely.
With all this instable movement in the knee your meniscus will take additional stress and becomes damaged – don’t be surprised of an early onset of athritis.
I tore my ACL – How long will it take to repair? Do I need surgery?
I’m going to cut straight to the chase here – unfortunately your ACL will not heal, and you will need surgery.
Why will it not heal? Your knee has a synovial membrane inside which contains synovial fluid, basically a small water balloon around the centre of the knee with a fluid inside to keep everything lubricated. To the bane of every ACL victims life, the ACL is located inside of this balloon. The body’s response to a torn ligament is to bleed, when bleeding occurs a blood clot will form to stop the bleeding and allow repair of the damaged ligament. However the fluid found inside the synovial membrane does not allow blood to clot and therefore the body is unable to repair your ACL.
“I can’t believe it, I’ve a Grade I ACL injury, I’m done for!!!”
You’ll hear your Doctor talk about Grade I, II or III injuries – these are classifications as to how bad your injury is. The higher the grade the worse it is (although it seems the illogical way around for me!).
- Grade I – Microscopic tears, your ACL may be stretched out of shape but still functions. If your injury is Grade I you’re lucky. Unlucky Rating: 0/5
- Grade II – Partial tear, increased knee instability and susceptibility to further knee injury. Unlucky Rating: You should have broke your leg instead.
- Grade III – Complete tear, your ACL is in two parts and your knee will be very unstable. Unlucky Rating: Or broken both legs.
Grade II and III injuries will require surgery to return your knee to normal functionality however surgery is optional.
In my opinion surgery should not be a choice but a necessity where there aren’t other health issues (old age). Anyone who participates in high-level sport where running and changing direction is involved (Football, Rugby, Basketball, Tennis) will not be able to continue without surgery. Those who do not participate can elect not to have surgery, but I question why people would choose to live the rest of their lives often with the feeling that their knee is going to give out, suffer numerous knee dislocations, deal with their knee locking and increase their chance of athritis.
Straight off the bat I want to put your mind at ease with surgery – you’ll be under general anaesthetic and won’t feel a thing. Speaking as someone who has had general anaesthetic twice previously I actually quite like it, what’s better than falling asleep instantly! It’ll be administered through an IV already in your hand and you’ll be fast asleep within 5-10 seconds, you’ll wake up instantly in post-op with a brand new ACL in your knee.
Your ACL will be reconstructed in one of three ways:
- Patellar autograft – Fibres are taken from the patellar ligament found between the patellar (kneecap) and tibia (shin), it is common practice that the middle 1/3 of the ligament is removed with bone fragments still attached either end.
- Hamstring autograft – Fibres are taken from an accessory hamstring (semitendinosus) leaving the primary part intact. Fibres are also taken from an accessory adductor (gracilis) again leaving the primary part intact. The resulting two fibres are often folded in half and braided together to produce a strand four times as thick as a single fibre.
- Allograft – The same as above, however the fibres are taken from a donor.
Grafts are threaded through a hole made in the femur and tibia before being screwed into place, et voila! A new ACL.
With the patellar grafts over time the bone fragments will fuse with the bone at the anchor points, giving a stronger fibre/bone attachment (as the fibres were removed in situ).
Ultimately which graft is used is down to your Surgeon although there are advantages and disadvantages to each one. I will cover this in a seperate entry in detail.
Surgery – When?
It has been a long standing view that surgery should be delayed for at least 21 days however this view has been disputed. In one study (Bottoni, C.R., 2005) that compared early surgery (9 days post) with delayed surgery (6wks post), results showed there were no differences in final functionality of the knee. Although those who had early surgery prevented potential additional damage to the meniscus and quicker recovery. The cause of longer recovery in delayed surgery is that the body has to recovery from trauma twice, from the initial injury and then again from the surgery. Early surgery means the body has to recovery essentially from one trauma. Sports professionals will have surgery as soon as the swelling has gone to reduce recovery time, however for the average Joe early or delayed surgery has no effect on the final outcome. What is important is the condition of the knee pre-op, in that it needs to be in good physical condition with a good range of motion – this will prove beneficial in post-op recovery.
Recovery and Rehabilitation
Recovery will be a long road. While some patients may be able to weight-bear or even walk on the same day as their surgery, their full recovery (participation in sport) will not be obtained until approximately 9 months post-op with some patients often taking upto, and even beyond, 12 months. The reconstructed ACL will be fixated taught which causes the decrease in the range of motion of the knee (alongside the swelling). This is so that when the knee is conditioned again the reconstructed ACL will stretch to its required length, rather than fixate it with less tension in and it becomes slack in time.
Rehabilitation will involve plenty of Physio sessions, the early months will aim to regain full mobility of the knee, before regaining and increasing strength of the quadricep, hamstring and calf. The most dangerous phase is the 3-7 month period, this is the time patients gain full mobility of their knee and begin to eagerly exercise again and sometimes overdoing it.
If you have anyquestions or would like to see something covered please leave a comment and I’ll get to it!