Right now I'm sitting at my desk, my legs are moving at 0 rpm, and my knees aren't complaining. When you sit at a desk or table, do your knees complain?

I don't think the problem is low cadence.

Back in ‘74 us young lads heard that the serious bikers were doing 60rpm and that was our standard. Today? On my Cannondale Criterium, probably 80ish.

Of course low cadence, by itself, is not the problem. But low cadence, particularly during climbing, is a proxy for higher force. And that higher force aggravates a knee that I twisted in my middle 20s. It's pretty hard to push that hard with a cadence in the 80-90 rpm zone, where that knee doesn't bother me.

Low cadence/higher power aggravates my knee (lingering injury from a crash two years ago). Higher power/higher cadence doesn't...

Not an issue unless I'm climbing.

Low cadence is a poor proxy for high force. I can pedal slowly with either low or high force. I can pedal quickly with either low or high force. Now that many of us have power meters, it's (way past) time to dispel the notion that low cadence hurts knees. In fact, even when climbing, once you've run out of gears and you're in your lowest, lower pedal force and lower cadence are directly (not inversely) related. That is, for any given gear, if you want to reduce force, slow down; don't speed up.

Muscle power into the cranks is equivalent to torque. And at low RPM, it takes more torque to maintain the same speed than it does when at higher RPM.

So more torque means more strain on the knees to wear their joints out over time and for the quads' to tire them out and cramp them quicker during prolonged effort.

Stop right there. Power isn't equivalent to torque.

I'm not talking about that kind of power. The power you are talking about is watts and that is over time. I'm talking about the muscle being put into the crank at that moment. That's torque. Which isn't over time.

I understand your point, but for a given power output lower cadence is harder on your knees. When you have run out of gears on a steep climb and you still need to produce say a minimum of 250W just to keep moving forward, then it gets pretty hard on your leg muscles and joints. A lower gear would be welcome at that point even without reducing power.

Pedal force is really what he meant, which is equivalent to torque in this case.

There's no evidence that muscle force, per se, is bad for the knees. In fact, the available evidence supports the opposite conclusion, e.g., multiple studies show running prevents knee osteoarthritis, and resistance is an important part of joint rehabilitation. Cartilage is a living tissue which, like other tissues, responds to use with hypertrophy. What injures joints is force in the wrong plane or applied to an inadequately stabilized (weak) joint and, of course, once a joint is injured its tolerance for force decreases.

So what you're arguing is that torque is equivalent to torque??? OK, I agree with you on that.

If you've run out of gears going up a steep climb, then slow down. In that case, decreasing cadence will decrease, not increase, crank torque. (To be fair, crank torque in that case is almost independent of cadence -- but to the extent that it's not, decreasing cadence will lessen crank torque; it definitely doesn't increase crank torque.)

I can go along with that. But it seems that more force when in the wrong plane will destroy quicker than a tinier force in the wrong plane. And more than quite a few people don't listen to their bodies when the body is trying to tell them somethings is wrong.

The net result is still that using low cadence with lots of muscle will cause more knee issues. Even though the real cause was they didn't have their cleats adjusted or feet angled properly to give the knee free movement through out all of their pedaling. Particularly the power stroke where they ignored the signs because other normal things hid them.

Who wants to slow down when everyone else on the group ride are climbing faster? If a lower gear is available, then spinning a faster cadence will let one top the hill with pretty much the same watts expended for the time it took to climb as anyone else used that finished in the same group no matter what cadence any individual was at.

If a person is in the easiest gear on their bike often for the hills they routinely climb, then that needs to be addressed by getting the proper gearing.

Oh, I've looked at this, too, and I agree with it. But at the moment I'm fighting the "slow cadence hurts your knees" fight. Later on we can move on to the high pedal force fight.

When you're lifting in the gym, does keeping your reps above 70 reps/minute prevent knee pain?

Lifting in the gym is usually for resistance training of your muscles. The bike is the wrong place to be doing resistance training. The bike is for aerobic and anaerobic training of your cardio vascular system.

My sore quads after a tough climbing ride have a different opinion.

I agree, but we may be outnumbered by the one-leg and low-cadence drill proponents.

But bro, are you swole?

My buds sometimes call me "Chicken Legs", so what's the opposite of swole?

I'll get to the gym. One of these days, when the quads are not already sore.

Swole is a good look for the elderly, or so the longevity people say. Might erode those great P/W numbers, though.

Everyone should do what works for them. That said I don't worry about using a big gear some of the time. Way back when I was still young some of my buds marveled at the fact that I was often on the big ring on some fairly hard climbs. I semi jokingly said I was saving my thumbs because I was sure they would fail before my knees would. Well here I am at almost 73 with healthy knees and nearly constant pain in my thumbs and wrists for the past few decades.

Even as an old codger I still use a wide range of cadences. I spend a lot of time at 90 rpm and even some at 100, but I also climb at 60 a lot and sometimes less maybe at times a good bit less. I am pretty sure if I ever do blow out my knees it won't be because I don't spin like mad all the time. I suspect that in general pedaling at a variety of cadences is probably best for joint health.

Just my opinion though.

The problem is that overrunning clutch (it goes by different names) hidden somewhere in the back of almost everyone's bike.

If you pedal at a nice slow cadence and with decent pedal pressure, that clutch never overruns and 100% of your pedal effort is translated into increased speed. Not a bad way to ride. It works. This is how I ride.

Now, attempting to increase your cadence by gearing down brings you away from that 100% efficient comfort zone. It brings you closer to the point where your clutch disengages and you are simply pedaling for effect with zero pedal pressure and zero power transmitted to the wheels. Wasted energy.

Other common vehicles you may be familiar with don't feature an overrunning clutch. A manual transmission car, for example, locks the power to the wheels and functions essentially like a fixed gear bike. An automatic transmission car has a fluid coupling, so if the power is faster than the wheels, that fluid starts to drive vanes in a torque converter, and the car accelerates.

If you really want to develop a faster cadence, you have three options. You could simply accept that you will spin out the overrunning clutch from time to time and lose power. Second, you could increase your momentum (typically by going faster). This makes it easier to keep from spinning out because physics will encourage your bike to keep moving at the speed it is at. Finally, you could learn to sense the pressure on that overrunning clutch and pedal just slowly enough to keep it engaged.

Of course decreasing cadence will decrease power in the same gear if the slope is a constant. But if you are maintaining power as the slope increases then pedal force will increase at a constant cadence or often increase even with a falling cadence. The whole point of gearing is to balance cadence against pedal force for a given power output. Running out of gears means you lose that flexibility and pedal force inevitably ends up higher than you would prefer when you have no more lower gears. Slowing down is often a limited option by that point.

Whether or not a high pedal force and low cadence actually hurts your knees is really a different argument. It certainly hurts my leg muscles and increases joint loading.