Leg Extension Machines–Good or Bad for Knees?


Is leg extension bad for knees? This question is a hotly debated topic in gyms, making the leg extension machine a controversial piece of equipment. There’s no other machine that isolates the quadriceps muscles quite so well.

Will a Physical Therapist Recommend a Leg Extension Machine?

The answer is that it depends on your injury. If, for example, you hurt your anterior cruciate ligament (ACL), your physical therapist will be more likely to recommend a rowing machine.

How a Leg Extension Machine Could Hurt Your Knees

If your knees are perfectly healthy, this amount of shear force the machine places on the ACL is bearable. Where problems might occur is when the quadriceps put out a stronger force than your knee flexors can handle.


Under normal circumstances, this would be unlikely to occur. If, however, you’ve been doing a lot of these exercises to redefine your quads, it’s possible to create an imbalance in strength. This is because these machines target the quadriceps very well but do little for the other structures of the legs.


They do not, for example, engage the hamstring connected to the knee. This supportive tissue prevents you from wrenching your knee when it’s under a great deal of pressure. By performing leg extensions with heavy weights, you actually increase the risk of injuring your knee.


A further danger is that the kneecap may slip to one side or the other.


Using this machine while recovering from a knee injury could set your progress back significantly and result in knee pain. Considering the limited number of muscles you work with a leg extension and the risk for injury, a rowing machine makes better sense.

Why a Rowing Machine Is a Better Choice

Rowing, on the other hand, strengthens the knee muscles and works the quadriceps. In addition, it also flexes and extends the hamstrings, strengthening the supportive tissue around the knee.


Leg extensions will strengthen your quads but little else. Rowing gives your whole leg a workout and helps build its core strength. This improves the stability of the knee joint and reduces the risk of pain and injury.


After an ACL injury, rowing can help you recover when combined with other exercises.

Rowing Saves You Time

Rowing is a full-body exercise that blends resistance and cardio training. If you have a limited amount of time to spend in the gym, a rowing machine is a great place to start. You can work all the major muscle groups and raise your heart rate.


According to the CDC, using a rowing machine can burn between 3.5 and 7 calories per minute.

Is Rowing Safe?

Like with any exercise, there are risks worth considering. The primary cause of knee injuries while rowing, however, is poor form. It’s vital to learn more about the correct format for each exercise before trying them on your own.


To that end, it might be helpful to hire a personal trainer to teach you how to use the machine properly. You could hire them for a couple of sessions to get you off to a good start or continue to work with them.

Other Benefits of Rowing Machines

Some additional benefits of rowing machines include:


  • Minimal joint impact because you are not pounding the pavement
  • Complete muscle workout because you engage all the major muscle groups
  • High-calorie burn because of all the muscle groups you work
  • Compact design that you can fold up and put away

So, is a leg extension bad for knees? Read more about alternatives by browsing the For-Knees website. You’ll find interesting articles and honest reviews on a range of products.

Other Exercises for Bad Knees

Of course, while leg extension machines may cause issues, it’s also true that rowing machines, while an excellent alternative, are not the be all and end all. You can, for example, simulate a cable row at home.