Bicycle Knee Soreness-Not

Introduction
From time to time I have heard of or have been involved in conversations where a biker (bicyclist type) complains about having sore knees after riding, even if only on rides of fairly short distances (<10 miles). Not being a doctor, I can't make any professional medical pronouncements on this condition but I want to take a few minutes to share some experience I have on the subject. If it works for you, great, if not then "Big Disclaimer, yadda, yadda, yadda... ;-).

I have had sore knees in the past from running on hard surfaces and from many, many hours in the gym practicing and playing volleyball. Bicycling, walking and cross country skiing are now my preferred exercise modes primarily because they are very low impact. But when I first started logging a significant number of biking miles (15-16 years ago), I would occasionally come up with sore knees too. The resolution I quickly arrived at was pretty straightforward, primarily involving "fitting" of the bicycle to my body flavored with the addition of some understanding about the mechanics of how the body handles the motion and effort involved in propelling a bicycle. Please note that this article is primarily directed toward standard bicycle frames and not recumbent bicycles, although the main principles apply to both.

Background
There are 4 important elements to consider if you want to get the most out of your bicycle riding time while avoiding sore knees. These are:

1. Correct frame size for your leg length
2. Correct setting of the saddle position
3. Monitoring pedal cadence while riding
4. Monitoring your heart rate while riding

Follow The Steps
The first two items above comprise the elements of fitting the bicycle to the individual (you). Items 3 and 4 complement the (now) well fitted bicycle and rider, providing real time feedback to ensure the most efficient return on exercise time as well as providing awareness of proper pedaling effort... very important in terms of preventing injuries or chronic pain conditions from occurring. More detail is presented step by step below.

Step 1.
Taking the time and effort to get the proper frame size is crucial to everything that follows. I recommend that this be done with professional guidance at your Local Bike Shop. Generally, the longer the rider's legs, the bigger the frame that is required. As an example, for me at 5'10", the correct frame size (for my 2007 TriCross Sport bicycle) is 54cm. There is a fairly close correlation between frame size and overall height but I recommend paying attention to your inseam size (mine is 33"). At any rate, the variables here clearly lend themselves to "on the bike" measurement by someone that does this type of thing regularly.

Step 2.
Once the proper size bike is available be sure to take the time to ensure the proper saddle height. This is as important as step 1 and must never be neglected. To set the saddle height, first get the saddle in an approximately appropriate "fore-aft" position (don't worry too much about this yet). Then sit on the saddle (holding yourself up by a wall or the side of a car or with assistance from a companion) and, with normal riding shoes on, place the heel of your foot on either pedal with the pedal in its fully "extended down" position. If the leg can be just straightened completely (with no noticeable bend), you are set. If the leg is bent then the saddle is too low and must be raised. If the heel cannot comfortably reach the pedal with the leg fully extended then the saddle is too high and must be lowered. Adjust the saddle and check again until the height seems to be right. And be careful to ensure that the seat post is inserted within its proper (marked on the post) range.

It may be necessary to iterate the "up/down" and "fore/aft" a few times to get it right. Fore/aft saddle placement is best done by holding a string with a weight (use a large washer or a nut) against the outside base of the patella of the knee while sitting on the bike with the foot (not just the heel) properly placed on the pedal and the pedal in the fully forward (crank parallel to the ground) position. The string should exactly intersect the axle of the pedal. If it is forward of the pedal axle, the saddle must be moved back and if it is back of the pedal axle, the saddle must be moved forward. In either case, if saddle movement is required, the vertical position of the saddle should be re-checked to ensure that it is still correct. Some personal leeway is generally applied regarding fore/aft saddle position. Many riders prefer, for example, to set the saddle back just a little as they feel it adds more power to the pedaling stroke. If you feel you do need to deviate from the fore/aft positions outlined here, I recommend the rearward direction over moving the saddle forward as it implies less pressure on bent knee joints.

An interesting point about vertical saddle position is this: in order to make the most effective (and efficient) use of the legs, the rider should never be able to easily touch the ground with more than the tips of the toes when sitting on the saddle. This means that dismounting is accomplished by removing one foot (say the right one) from its pedal, standing on the other (the left) leg and then bending that supporting leg to lower the (right) foot to the ground... all the while braking in a coordinated fashion to complete the stop. It's my opinion that most sore knees happen to inexperienced riders who feel insecure if they are unable to put their feet down flatfooted on the ground while still sitting on the saddle. When a bike is set up in this fashion, as noted above, the saddle is set too low. The result will always be that the legs are not allowed to reach their full length (and maximum power) when pedaling and, I think, this is what strains the ligaments of the knee, causing the soreness.

Once steps 1 and 2 are completed to the rider's satisfaction, the importance of using the bicycle's gearing system properly moves front and center as the key to items 3 and 4. Items 3 and 4 complement each other and they are intimately joined by use of the mechanical advantages given by proper selection of the front and rear gears of the bike.

Step 3.
Monitoring pedal cadence (i.e., RPM of pedals) is relevant to both efficient use of the engine (the rider's body) driving the bicycle as well as the condition of the mechanical linkage (particularly the rider's knees) upon which power transmission to the pedals depends. It may be easiest to think of this in terms of how a car's engine and transmission interact. The principles are identical. For example, when driving a car with a standard transmission (say, 5 speeds) one starts off in the lowest (or 2nd lowest) gear. The reason is that there is more mechanical advantage in the lower gear and, although the top speed of the car might only be 15 or 20 mph in the low gear, extra power is provided to the wheels to get the mass of the vehicle moving. Without the gearing system, the car might require a 1000 horsepower engine to both "get started" as well as to cruise on the interstate. Efficiency would definitely suffer if this were the case.

In terms of the bicycle rider, and the issue of sore knees, efficient transmission of the rider's muscle power to the pedals means that extreme stress on the knee ligaments is avoided by proper gear selection. In other words, riding in "too high" a gear at slow speeds will put strain on the knee joint. So gear down as appropriate to how fast you wish to ride. While there's generally no additional strain involved with "spinning" pedals too fast (i.e. too low a gear when traveling at relative high speed), riders almost naturally seem to shift up (as well they should) when that occurs.

Step 4.
As promised, this step ties in to the 3 preceding elements by allowing the rider to monitor the condition of the "engine" (you... and your heart) in various states of gearing and effort expenditure during a ride. Pedaling cadence, gearing and the rider's heart rate (or amount of effort being put into the ride) are intimately related. If you don't know your aerobic exercise range of heart rate, please take the time to find out what it is (google will do a good job helping you learn this) and be aware of the numbers as you will use them regularly if you follow the precepts presented here. My range is from 125 to 150 beats per minute (bpm). A heart rate below the low value means the body is not being as efficient as it could be at, for example, burning fat... or at utilizing the carbohydrate produced energy of the body to get the best speed for the least amount of effort. The goal is to maximize the amount of time spent in your aerobic zone. To this end it's useful to use a heart rate monitor (HRM) on the bicycle.

Putting It All Together
With a properly fitted bicycle, monitoring one's heart rate to keep it in your aerobic zone while simultaneously keeping tabs on pedaling cadence for a preferred value (for me, 80-90 rpm feels right) will give the rider the best riding performance and least stress on the knees. For example, if, in my case, my heart rate drops to 110 and my cadence is 95, it's time to shift up to a higher gear. That will make my heart (or me as the "engine") speed up as I work closer to my body's maximum efficiency regime. So I might shift (back rings) from 6th to 7th. Whereupon I will immediately notice the cadence dropping (to, say, 85) and my heart rate should increase (to, say, 120). In this case, I'd probably shift up again to 8 and put more effort into pedaling to get my heart rate up to about 130 and keep the cadence at around 85. Well, I think you get the idea.

Conversely, if my heart rate should go significantly about 150 (my maximum for aerobic exercise), I'd probably adapt by shifting to a lower gear, reducing the pedaling effort... and see the heart rate drop to, say 140. Meanwhile, I'd keep paying some attention to the cadence so that it leveled off again at the (favorite) 85 rpm rate.

A quick word of caution: be sure to maintain your concentration on riding safely and with due attention to people and other bikers on the trail or to traffic around you if on the road. As always, riding should be an enjoyable experience. Hopefully this article will be useful to those that have been trying to solve sore knee problems when bicycling. Feel free to comment.