aching knees

Beginner here … wondered about possible reasons both knees ache after practicing for about 45 minutes. :thinking:
It’s at the top of the knee where the Quad muscle attaches. Possible reasons I’ve come up with are:

  1. cranks are too short (114mm)

  2. seat is too low

3 muscles not yet used to the strain

Insights appreciated…

I have been diagnosed with quadricep tendinitis numerous times because of riding. Simple fact; unicycling will eventually hurt your knees.

My recent injury is a slight dislocation of my kneecap due to a misalignment and weakness in my hips. This again was from riding. Well it was a 16mile mtn bike race with 4000 ft of climbing that has never been unicycled before lol.

Long cranks will help and a taller seat too. I think it might just be that you aren’t used to using those specific muscle groups yet. Takes a while to get used to everything. If your knees hurt then stay off the wheel for a few days.

my .02

#2 is most likely your issue. Make sure that when you leg is at the bottom of the pedal stroke, you leg is almost extended.

Count me in for seat too low.

Your leg should fully extend as you ride. When doing tricks you can lower the seat for some extra room but when riding, your legs should fully extend.


I think foot positioning could be a factor. I get pain there if I ride with a short seat and my feet on the arches. If I position my feet on the balls and make sure they are aligned straight it doesn’t seem to have the same pain. The muscles not being used to it could be a factor. Take it easy for a bit and try again!

I disagree with C9ollie about longer cranks helping since longer cranks would require more knee movements and might amplify the effect. It would only help if your knees are used to long cranks I guess. I think it is a simple fact that doing years of unicycling will strengthen your knees, not hurt them, my experience differs from yours.

Keep putting your seat up until you stretch to reach the pedals, then put it down a bit. Seat too low is the easiest hypothesis to test.

Relax into the seat and let it take your weight rather than standing up on the pedals too much. Being too tense can make unicycling seem harder than it is.

I am also a beginner having the same issues and have to agree with most of what c9ollie said. I was diagnosed with tendinitis as well. I thought my seat was at the right height, but it was 4 inches too low. That made a HUGE difference. Longer cranks means you don’t have to pedal as hard, but I found shorter cranks 137mm to work better for me, it’s mostly a personal thing. Lastly, as time went by and the legs got stronger the knee problems got less and less.

Keep it up, it’s worth every second of effort.:smiley:

What size wheel are you using?

I think it’s possible the cranks could be the problem, 114mm are, IMO, way too short on anything except a 20" wheel if you’re having knee problems.

One problem with very short cranks is the leverage- on rough ground I found that short cranks can ‘grab’ and require a hard push to power through, which caused (with me) a noticable stress on the knees, whereas, with longer cranks (I use 150’s on my 24x3 and, have recently been riding 2-5hrs a day with zero knee issues) I’m able to smoothly ride through the same conditions with no knee stress.

How ‘beginner’ are you?
What sized wheel?

I had learned that the basic way to set the seat height was to sit on the seat with your heel on the pedal. Obviously you have to hold onto something…

I always wonder about the short/long pedal thing with regards to knee health. The professional cyclist do lots of miles and I’m sure they don’t run small pedals. We have a crank issue because that’s how we gear ourselves (except for the Schlumpf people :wink:

But most importantly, have a rest and then take it carefully. You don’t want the knees to get worse…


I have been wondering if knee pain could result from some small lateral movements we do to regain balance.
I found a counter measure and it is to practice in-line skating: first your knees ache then they get stronger … (no scientific proof supports this experience :D)


…to some of the questions…

I’m riding my son’s Sun 20" w/ 114mm cranks.

Only been riding a month…can go about 100’.

I’m sensing the “leverage problem” as those cranks really do feel short, but my comparison is to a bicycle and I really don’t know how it is supposed to feel. I’ve never had this knee pain on a bike…so I’m trying to figure out what the problem is.

I do have a Nimbus Muni 24" showing up on Tuesday (150mm cranks) so it will be interesting to compare the difference.

Also, with so many mentioning the seat height, I’m thinking that this is an issue for sure. My legs do not extend all the way (w/ some bending). My 8 year old had me cut the seat post a year ago last summer so he could reach the pedals… it must be a little too short.

Please let us know how the 24" muni with 150mm cranks goes, when you’ve ridden it a couple of weeks.

I’m guessing that your knees will be a lot happier than with the 20" wheel and 114mm cranks- personally, I’ve always found 20" wheels uncomfortable and more prone to hurting the knees- especially ridden outdoors on imperfect terrain.

Like I said above, my setup is a 24x3 with 150’s, I’ve been doing 2-5 hrs riding/day recently, with no knee issues (and my knees are 45 years old and not in the best of shape).

Do work on getting the seat height right (though I have mine set a little below ‘leg almost straight at full extension’ just to give me some leeway of rougher terrain) as it is common with many beginners to have the seat tto low.

On other thing, that no-one has mentioned: as my knees are old and not in the best of shape, I do keep a mental focus on them when riding- if a particular thing causes any kind of twinges, I notice it and really endeavour to not do that thing.

So, if I’m going down a steep hill, for example, I keep control and go down relatively slowly using my leg muscles to not let the unicycle pick up speed (‘run away’), because I don’t want to put myself into a position where I have to suddenly apply a huige amount of force to come to a sudden stop.

Congratulations on riding 100’, that is a good start!

114mm is definitely not too short for a 20". A 20" wheel requires very little force to move and 114mm is a good size- I use 100mm cranks on my freestyle uni. I use 114mm cranks on my 36" wheel and it only occasionally lacks power but makes up for it with top spinning speed. The only reason you might not feel enough leverage with 114s on a 20" is if you are pushing too hard on the rear pedal while trying to go forwards. Relax and push gently on the pedals rather than fighting them.

The Nimbus MUni will offer you some things to compare, and the higher seat height should be helpful. If you ever want to ride your son’s unicycle you could get a longer seatpost for it.

There’s another reason 114’s may lack leverage i.e. the laws of physics :slight_smile:

Fact is a short lever will always be able to exert less leverage than a long one. That’s why, if a bolt is stuck/tight, a mechanic, having failed to shift it with his/her spanner, will go and get a longer spanner.

It’s also the reason why 150mm+ is the accepted length for muni, and why no-one deos muni with 114mm cranks.

Accepted by whom? And why do you refer to many people as no one? I seem to have missed out on a copy of the MUni bible which you are quoting.

And why are you posting this in a thread about a 20" learners unicycle? The weight of a small wheel does not require large levers to move, and 114s have easily sufficient leverage. 150mm is indeed a good size for MUni and I use it on my 29er.

The laws of physics say that 114s on a 20" are good according to this thread, and that they are the same as 145s on a 24, and like 175s on a 29er in the amount of gear ratio gain.

You remind me of when swore by ancient wisdom that 170mm cranks are best for 24x3" wheels, and that without them your terrain must not be steep. Then Kris Holm tended towards shorter cranks and they quietly removed their silly long-crank advice from the pro-muni pages.

It’s pretty accepted that 24x3 with 150’s is the best length for muni.

I believe Kris Holm mainly used 170’s on his 26" muni in the early days- so i guess that’s why, when people first started switiching to the (then) new 24x3, they tended to keep use 170’s.

And then, it turns out that 150’s tend to be better, for most muni, and, defintily better for general riding, so they then moved to them.

Personally, I never used 170’s, much preferring the 150’s.

today’s practice

A quick update…

I went out for about 45 minutes of practice last night and, although I felt some slight pain in both knees (more accurately above the knee), I felt pretty good afterward and the aching isn’t as intense the next day.

3 days until the Nimbus Muni gets here… Can’t wait :slight_smile:

For whatever it’s worth, I started learning to ride at the end of March (on a 26er). I eventually started free-mounting and am currently alternating between flat-ish gravel paths and more varied dirt trails. 1-1.5 hours of riding covering up to nine miles.

I had the same knee pain and found taking a day or two off between sessions gave my legs time to recover and my mind to think about what I was trying to do. I still get some pain but not nearly as much as before. I suspect my uni muscles/tendons have been developing over the past five or so months.

Previous posts on seat height are spot on. The legs should be quite close to full extension at bottom-dead-center.

Keep working at it, take your time, listen to your body and keep it fun!

Thanks for the encouragement

My boys “ride circles around me” (pun intended) :smiley:

They challenged me to ride (as I had done to them), so I couldn’t say “no”.
“Come dad, you can make it to the leaf today,” they all say with a grin. Actually, the younger two just learned about 1 week ago, so I have 4 that ride.

It’s a fun family activity.

I remember having knee pain the first few months of riding. It was most bothersome when I started doing downhills. I put brakes on and rested a day or two in between longer rides. Over a few months time the knee pain went away. I get a twinge now and then, but it never lasts long (knock on wood). Now I don’t use the brakes much on downhills unless I’m riding shorter cranks. knee pain seems to be a fairly common complaint for new riders.

New Uni

Ok…UPS dropped off my new Nimbus Muni 24" today.

It made all the difference in the world. I practiced for about 90 minutes today with no pain at all. I believe it was a combination of seat height and crank length…but mostly the seat height.

I think, too, that some of the muscles required to ride a unicycle were a little out of shape…so the general soreness and lactic acid may have also been an issue.

Riding this Nimbus increased my distance 50% right off the bat compared the the 20" Sun. Glad I made the purchase. :D:D