Are leg extensions bad for knees?

[gspieler]

You'll almost never see a PT loading more than 10lbs on a long arc quad movement. It can be used for strengthening, improved ROM, and to relearn VMO control to improve patellar tracking. The last 30 degrees of terminal knee extension leaves very little surface area between your patella and femur during articulation which may cause the cartilage to wear away prematurely which is why alot of people don't advise that you load up a leg extension machine with crazy amounts of weight.

When done in the correct fashion and loaded appropriately there's little risk of harm. If you're throwing the weight around like Cain Valesquez then you're probably gonna have a less than stellar outcome. If you're trying to equate physical therapy with bodybuilding/ strength training then you aren't going to see 100% congruency.

+1.

 

[deadshot138]

In short they are a shit exercise with poor cost/benefit ratio

 

[Zankou]

I wouldn't say they're an inherently dangerous lift; they do seem to have a clinical function, when done with strict form and with little resistance. That said, I do beleive the way most lifters do them(relatively heavy weights, not controlling for velocity/momentum) is likely a detriment to the overall integrity of the patella. Quite simply, it's a biomechinically disadvantageous position, and places a lot of shearing force on the joint.

Bottom line(for me) is that any benefit is far outweighed by risk with this lift, so I won't do it unless prescribed by a PT, etc. This is particularly the case given that there is virtually zero carryover to sport and/or ADL's, and there are vastly superior ways to train knee extension and increase strength/hypertrophy in the quads. I don't see the point of doing them in a universe that contains squat, lunge, leg press, etc variations. Just my .02.

This. They are useful for near-cripples doing PT, but inferior for almost anybody else.

 

[Robocok]

- Guy with more posts than me in a shorter period of time

I'm a black belt bro. Get on this level before you address me.

 

[JimRussel]

I'm a black belt bro. Get on this level before you address me.

I’m working on it bro. There’s no material to post on around here anymore. Barely anyone with actual lifting questions/issues, barely anyone even making good troll threads.

My wheelhouse is helping with exercises and form check videos. No one does those around here anymore. They used to be quite common. This forum fully taught me how to lift back in the day with the use of fork check videos. Like literally the posters here and my own research are the only reason I know how to lift.

@MatterOverMind was one of them. I think he’s about the only one left here now.

 

[JimRussel]

I’m good at helping people tweak their technique and lift execution in person, but I think that just comes with experience. And there’s no e-cred, so who even cares.

 

[Sano]

Leg extensions aren't necessarily bad. Time and place, as with most exercises. It's true that there is more sheer force in the patellofemoral joint, and that it can aggravate issues with patella tracking, but it has clinical use. Even outside of rehab, many people will be able to load it moderately without having issues.

In regards to rehab, leg extensions can be useful in the subacute phase post-op of tears and the like. Terminal extension (last part of knee extension) is usually severely compromised in the early stages and it's important to work in that range. Both for VMO development but also for a variety of reasons which effects long term prognosis. You can work the range without a leg extension machine with other exercises, but putting someone in a machine and being able to control load at the right time can improve compliance. At the same time, for something like arthritis and patelofemoral pain I usually opt out and find alternatives, especially if it aggravates pain. It also doesn't have a lot of "bang for the buck".

Not the biggest fan, but it does have merit under certain circumstances.

 

[SalvadorAllende]

They are not.

Banging the weight while doing them is probably not good tho.

 

[Ian Coe]

I do them when I can (ie have access to gym with them) to build the muscle to lessen the impact of hiking downhill with weight.

 

[Ackmed]

Listen to your body. If it feels good on your knees, continue doing them, if they hurt then don't.

What's good for person A isnt always good for person B.

My knees hurt if I start quads with any type of pressing movement without first warming my knees up with leg extensions. So even if various people on the internet said leg extensions were bad for knees I would continue doing them.

 

[Phlog]

I've thought about doing them, done them, then wondered why I was doing them and replaced em.

I imagine they are prescribed for people who are rehabbing a quad muscle whilst not activating the hamstring for some reason? Isn't it basically the same answer to why a physical therapist prescribes anything?

At least 50% of why I come to the S&C forum is to read your posts. You are fucking great.

 

[boingyman]

Only if your name is Cain

 

[ThunderL1ps]

They never bothered me until I had some knee valgus. There is really no point in Cain'ing it with this movement. A good alternative for a closed chain version is to walk backwards against a strong band (blue).

 

[TimeToTrain]

I would say leg extensions are safe because there’s minimal stress to the knees as oppose to squatting, clean and jerk, etc. The only bad thing I can find is the sitting position. Overall, leg extensions is like arm curling but for the legs.

 

[JimRussel]

Overall, leg extensions is like arm curling but for the legs.

Except one is joint flexion and one is joint extension. But you tried, bro.

 

[DoomPatrol]

Except one is joint flexion and one is joint extension. But you tried, bro.

I would also have to imagine the knee cap floating around the joint complicates things more than elbow extension. Even if you compared knee extension to triceps extension I don't think it's completely comparable because the joint structures are so different.

 

[gspieler]

I would say leg extensions are safe because there’s minimal stress to the knees as oppose to squatting, clean and jerk, etc. The only bad thing I can find is the sitting position. Overall, leg extensions is like arm curling but for the legs.

Define “minimal stress”. I’d argue basically the opposite. The squat is one of the most basic movement patterns in human biomechanics. Yes, they stress the knee joint. But, assuming they’re done correctly, stress the knees in a way the body was designed to be able to accommodate.

The leg extension, in contrast, places a lot of stress on the knee joint, but does so in a completely unnatural position. Call me crazy, but I wouldn’t describe ~200lbs pounds of angular force pulling down on your knees, as you are actively trying to extend them against this force in a seated position, as being “minimal stress” on the knee joint.

 

[Badger67]

I would also have to imagine the knee cap floating around the joint complicates things more than elbow extension. Even if you compared knee extension to triceps extension I don't think it's completely comparable because the joint structures are so different.

 

[DoomPatrol]

I guess that's all it takes to become a knee surgeon.