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ACL Tear: Causes & Symptoms

What is an ACL tear

by Premier Hospitals | February 15, 2023 |

What is an ACL tear?

There are two central ligaments in a knee: the posterior cruciate ligament (PCL) and the anterior cruciate ligament (ACL). The ACL is key for athletes who need to change direction as it allows control of rotation. Imagine the ligament is like a piece of rope with multiple fibres in it. When it ruptures, all those fibres break and it's like a rope that has been split into two pieces. It is possible to have a partial tear but it's actually really rare; almost all are complete ruptures.

What terminology will I hear?

You might hear the words “tear” and “rupture”. A tear is a rupture, so they are the same thing. Often, you will hear the phrase “Grade 1, 2, or 3” with a tear. The grading usually reflects the amount of laxity (looseness) and actually is a bit academic for an ACL rupture because, in reality, it's either gone or it's not. Partial tears do occur but, as mentioned above, they are rare. Unfortunately, on MRI scans, it can be hard to tell if the ligament is completely ruptured, so it may be described as a partial tear, which can be quite misleading. Most people who've been told they have a partial tear actually have a complete tear, which they need to get checked out.

How does it happen?

Two-thirds of ACL tears are non-contact injuries, so the player might make a sudden change of direction that goes wrong; usually, their studs catch or foot slips. The ACL stops the tibia (shinbone) from coming forward and twisting inwards, so the knee gets into a position where the rotational load is excessive Very occasionally, it can happen if the knee goes straight backward If someone's had a twisting injury to their knee, 75 percent of those people hear or feel a pop in the knee. Most of them will report some swelling within an hour or two of the injury. A patient would report one of two things: either a patellar (kneecap) dislocation, which is less common, or an ACL rupture.

How painful is it?

The variation is because there is a spectrum relating to the amount of damage that comes with an ACL tear. The degree of violence translates to the amount of damage you have. A lot of ACLs are ACL, plus meniscus, plus medial ligament — and the bigger the trauma, usually the worse the injury, and so the more pain. The other thing is that when the ligament tears, it bleeds and the knee rapidly swells. Usually, there is some swelling present within one to two hours of the injury.

What's the recovery process?

Over the years, we've learned that an ACL tear is not something that can be dealt with by physiotherapy alone (for others, non-surgical treatment is appropriate). Some ligament injuries, such as those to the MCL (medial collateral ligament) rarely need surgery but in pretty much all cases of ACL rupture, they are best treated with a good operation. After the injury first occurs, you have to get the knee “quiet”, which usually means a week or two of letting it settle down because if you operate shortly after a big trauma, you just add to it and increase the risk of stiffness. During this period, physiotherapy (prehab) is vital. When the person has the knee completely straight and can bend it to about 100 degrees and there's not much swelling, it's a good time to operate. Operation with a combination of the keyhole and open surgery. Stitching the ends of the ligaments together isn't reliably doing a reconstruction, not a repair — which means we place some tissue where the original ACL was. There are a number of choices for this never use synthetic ligaments, which people can get reactions to because of the polyester that's used also don't use donated tendons (someone who gives their organs for transplant will often give their tendons as well). It's an attractive option because you don't take anything out of your patient, you just plug in a new ligament. But since it's not your tissue, they don't heal well and the re-rupture rate is up to seven times as high. take a quarter to a third of the tendon at the front of the knee, between the kneecap and the tibia, which has a nice bit of bone at each end and I slide it in through a couple of drill holes that enter the joint at the attachment site, and fix it with a screw at either end. The first two to three weeks after the operation are all about getting the knee out straight and reducing swelling. You want the patient to be able to drive their knee straight with their quadriceps (thigh muscles). Bending it depends a bit on the damaged structures in the knee as a whole but usually, by two weeks, you've got a right angle of 90 degrees. Patients will be fully weight-bearing (after the operation) but they use crutches for balance for three weeks After about three weeks, once they have the knee quiet, they start a strengthening program. Then, at 12 weeks, the ligament has healed If it feels great, we can relax a bit, but then they need to restore muscle strength and control in the limb. Although improper rest and heavy workload on the muscle can re-break it.

Most common setbacks/secondary injuries?

The classic one we see is that because they're out for so long, they lose conditioning Someone who's done brilliantly with their ACL, comes back with a tear in their groin, calf, hamstring, or something else. It's just that they've lost fitness. The worry about the knee is getting back too soon before you're ready because, obviously, it can be re-injured. The most common problem, though, is loss of straightening and persistent swelling.

Is that part of your body left vulnerable going forward?

One thing we've learned is if we also tighten up the tissues on the outside of the knee (as well as reconstruct the ACL), it greatly reduces the re-tear rate. If you use a patellar tendon and graft and add this operation on the outside of the knee, the re-rupture rate has gone down to two percent, which is really low. The best-published figures before were about six to eight percent. Often, the person's final bit of physio is important.