“I just remember planting my foot on the ground and the knee suddenly twisting – and then I heard a huge crack.”
That was how Robb, speaking to us for a patient case study, described the moment he tore his anterior cruciate ligament during a Sunday league football match.
A major ACL tear is a significant injury. In Robb’s case, it led to mobility issues (he couldn’t fully bend his knee) instability (he was suffering repeated kneecap dislocations) and, ultimately, reconstruction surgery. When this happens, one of the key questions is: will the new ACL be the same as it was before? Let’s look at some of the answers.
Who is ACL reconstruction for?
ACL reconstruction is generally only considered for the most serious cases of ligament damage. That means things like major instability, a total rupture (where the ACL tears completely away from the bone), or additional issues in other parts of the knee. Robb, for example, had also damaged his MPFL and PCL.
How does the operation work?
Rather than stitching the broken pieces of ligament back together, the aim of ACL reconstruction is to replace the torn ligament with a completely new piece of tissue. Or, to put it in medical language, to replace it with an autograft. This is typically taken from your hamstring, or from another part of the knee like the patellar tendon. The graft essentially stands in for the old ligament.
Is the graft a like-for-like replacement?
No. It’s well suited for recreating the stabilising effect of an ACL – stopping the shin bone from moving too far forward, or the joint from over-rotating. But the tissue fibres, and the orientation of those tissues, won’t be quite the same as the original ligament. You could think of it as a kind of surrogate ligament, which seeks to replicate the form and function of a natural ACL as closely as possible.
What else is different?
The new ACL will be attached in a different way too. During surgery, the consultant creates two narrow tunnels in the femur and the tibia, the bones either side of the joint. The graft is threaded through the tunnels, tightened, and secured in place with a suspension device and / or surgical screws.
Will the new ACL work in the same way?
If the aim of ACL reconstruction is to restore everyday motion and stability, most people achieve that. “ACL surgery fully restores the functioning of the knee in more than 80% of cases,” explains the NHS. But it can be difficult to say exactly what that level of function will look like – particularly if, like Robb, you’re a keen sportsperson. Some people find they’re able to get right back to their highest levels of performance. Others struggle to do that because the biomechanics of their knee feel quite different. Sometimes people decide to adapt their game or even change sports.
Are you more likely to tear your ACL again?
We usually put the chances of re-rupturing an ACL at about one in 10. But of course it depends what you’re doing with your knees. Contact sports obviously carry a higher risk than walking. It’s worth adding, though, that post-surgery knee issues aren’t always related to the new ACL. When problems arise, it’s quite often due to injuries in other nearby knee tissues, such as cartilage damage or a meniscus tear. So the picture can be complicated.
What can you do to improve your chance of a successful ACL reconstruction?
In a word (or maybe three!): physiotherapy-led exercise. Improving strength, balance, and range of motion in the muscles that support your knee can have a significant impact on the overall outcome. You can find out more about that in this article: Why prehab is vital for ACL surgery. As Robb found, ACL reconstruction is an area where persistence really can pay off:
“One of the main aims [of exercise] is to build up the strength in the quadriceps, because if the ligaments do ever become a bit stretched in the future, those muscles will help to hold the kneecap in place,” he told us. “When I agreed to have the[…] operation, I knew it would involve a lot more recovery work. But I think it helps if you set yourself goals and stay determined.”
