Avoid Repetitive Knee Injuries While Riding A Bike

By: Michael Lovegren

Published: 2008-07-31

Introduction 

As gas prices continue to soar, more Americans are parking their SUVs and purchasing a bicycle to ride to and from work as an alternative way of spending money on fuel.  By bicycling to work, commuters will be able to reach their daily physical activity needs and help fight the problem of America being an obese nation.  But what if I told you that by riding your bicycle, you might be susceptible to repetitive knee injuries?  When you workout in the gym you’re cautious of your form, but what about when you are bicycling outdoors? This article discusses the importance of proper seat height and how to set up your bike appropriately to avoid such knee injuries.

Why do I need a proper seat height?

A common problem that cyclists and triathletes face is “overuse-also known as repetitive knee injuries.”(1,2) These injuries are associated with the cyclist having an improper saddle height caused by an improper bike fit. There are several methods that are used to get the proper bike fit; however, the best method recommended is a knee angle of 25 to 35 degrees to help prevent overuse injuries.

Having a seat height that is too low can lead to anterior (front) knee pain.  A low saddle height will cause excessive compression of the knee similar to doing an improper lunge.  Performing improper lunges after a while will lead to muscle imbalance and trauma to the patella femoral ligament.

On the other hand, having a saddle too high can lead to posterior (behind) knee pain. A high saddle will cause excessive extension of the knee, which leads to another muscle imbalance and posterior cruciate ligament or a hamstring tendon strain injuries.

Obtaining the recommended knee angles of 25 to 35 degrees will allow you to avoid knee injuries.  To understand how this may impact you, on average a cyclist produces pedal strokes of 90 revolutions per minute.  So if you are in a spin class pedaling for 40 minutes, this accumulates to 360 pedal strokes. Simply, 360 pedal strokes is similar to doing 360 squats or lunges either correctly or incorrectly. If done incorrectly, this repetitive motion can lead to overuse injuries in cycling with the improper seat height.

Before attempting knee angle make sure your seat is in the proper position:

Steps on how to accurately measure knee angles

Ride on the bike to find a comfortable position on the seat Spin crank arm until either left or right crank arm is in down stroke with opposing crank aligned up with seat tube angle (maximum trochanter height) Take goniometer and place on the outside (lateral side) of knee Have one arm of the goniometer aligned with the greater trochanter Other arm of goniometer aligned with tibia (shin bone) Measure the knee angle (recommended knee angles 25-35) If knee angle is lower or higher raise seat height until you have reached the required angles Repeat these steps for opposite leg

Don’t have a goniometer?

Here are some calculations you can take and apply to the bike Stand up straight with good posture Make sure you are wearing the shoes that you will be bicycling with Have a friend measure from the bottom of your feet to your greater trochanter (hip) Take this measurement and then multiply it by 96, 98, or 100%. (This number varies by your pedaling mechanics.) Use these measurement and apply to the bike Measure from top of saddle to pedal (make sure crank is aligned with seat tube angle) These measurements will allow you to be within the 25-35 degree knee angle.(3,4) (Trochanteric Height)  X (98%) = Seat Height

How to transfer information from bicycle to indoor bicycle

Here is a hint to help transfer these steps from your road bike to the spin bike. Once you have followed the steps above, take your ultimate seat height by measuring from top of the seat to the pedal in the down position, with the crank aligned with the seat tube angle. It is best to take these measurements in centimeters. Write down these measurements and then apply to your indoor spin bike.

References

(1) Peveler W, Bishop P, et al. Comparing methods for setting saddle height in trained cyclists.  J Exer Physiology Online 2005;8(1):51-55.
(2) Peveler WW, Pounders JD, et al. Effects of saddle height on anaerobic power production in cycling. J Strength Cond Res 2007;21(4):1023-7.
(3) Gonzalez H, Hull ML. Multivariable optimization of cycling biomechanics. J Biomechanics 1989;22(11-12):1151-61.
(4) Price D, Donne B. Effect of variation in seat tube angle at different seat heights on sub-maximal cycling performance in man. J Sports Sci 1997;15(4):395-402.

About the Author

Mike Lovegren, MS, NASM-PES, USA Cycling Level 2, is the content development coordinator for the National Academy of Sports Medicine. He has a master’s degree in biomechanics from the University of Northern Colorado and has a bachelor’s degree in kinesiology from California State University of Dominquez Hills in Carson, Calif.

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