In this blog I’ll be talking about if knee extensions are safe for your knees, why loading is good. And how regular training can increase your loadability. But before we can dive into this topic, I’ll give you a short lesson in knee anatomy. 

Knee extension anatomy

So let’s start with the anatomy of the knee. The knee joint consists of two joints. On the first hand the tibiofemoral joint, consisting of your shinbone, the tibia and your thigh bone the femur. But there’s also a patellofemoral joint, so your knee cap, the patella and your thigh bone, the femur. 

If we talk about the safety of the knee extension exercise. We mostly talk about the patellofemoral joint. So this is going to be the relevant joint for this discussion. Okay, let’s start with the most discussed opinion about the safety around knee extensions. And that is, that the knee extension is placing too much stress on the joint. 

Knee extensions are too stressful

And luckily there have been studies on this topic. In 1993 Steinkamp et al looked at the stress placed on the patellofemoral joint during the leg extension and the leg press at different angles. And they found that the stress on the knee was similar between the two groups. But the angles in which the stress was the highest were different between the two exercises. During the leg press, the stress was highest at around 90 degrees of knee flexion (a bended knee), but the highest stress came at 0 degrees of knee flexion during the leg extension (a straight knee).

In 2014 Powers et al did a big study where they looked at the compressive force during the squat, leg extensions with an ankle weight, and leg extensions with constant resistance. They found out that the forces were highest during 90 degrees of knee flexion during the squat and highest during full extension of the knee during both leg extension exercises. And the peak stress during these three exercises was highest during the squat. 

Knee extensions are less stressful

So looking at these studies, we can say that leg extension exercises aren’t more stressful for the knees than both the leg press and regular squat. In fact, the stress is even lower. But besides these facts. Is this stress even bad? Well, no. And I will tell you why.

Is stressing the knee bad?

If we want to make our muscles stronger, more durable, and less prone to injuries, we need to work out and we need to stress our muscles. And this is also the fact with your bones. If we place our bones under stress, we will increase the bonedensity of our bones. But most important is the fact that we need to slowly progress the intensity and frequency of our training load. If we do too much too soon, we will get injured. But if we slowly built up the load over time during the leg extension and train regularly, our body will adapt and will withstand the load. Causing an increase in training capacity. But if you stop training, your training capacity will go down, causing your body to withstand less load. 

What if your knee hurts during the leg extension?

Okay, this is all fun. But what if you’re in pain? What should you do? Well, you can do multiple things. You can stop doing your exercises, but I wouldn’t recommend that because your body will only become weaker. But you can try to decrease your training load, train slower, train at different angles, or get more rest in between sets. But most important is to understand that pain during an exercise isn’t always bad. If you want to know more about this, click the link up here to find out when to train through pain. 

Okay, I hope this blog helped you understand that the leg extension is just as safe as the squat and leg press and that loading is good for your knees. If you have pain and want to work with our online rehab guide. Click here to get your own FREE rehab guide. And if you need more tailored guidance, consider booking an online consultation with us.