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BikeDynamics - Bike Fitting Specialists

Bike Fitting Guidelines - Hips Knees and Ankles

Not necessarily a Fit Guideline, but you might like to see some of the typical knee and ankle behaviours captured by our motion analysis system.

Knee Tracking

Good knee tracking

In this case the knees are both tracking vertically and equidistant from the frame. A slight outward lean at the top of the stroke is due to parallax issues as the knee is closer to the camera at this point.

Lower body twist - offset knees

Although the right knee is tracking well, it is closer to the frame than the left which also moves further away at the top of it's stroke. This customer had a small leg length irregularity but was also asymmetric from a flexibility viewpoint.

Knees out!

Although a knees out stance is not helped by a low saddle height, it is largely driven by the hip joint and independent of bike fit.

Poor knee tracking

An inward lateral sway of the knees is very typical and often attributable to a fore foot varus angle. This case is quite extreme and was due to a strong dorsiflexion of the ankle joint resulting in foot inversion and so tibial inward rotation.

Ankle Behaviours

Surprisingly there is far more diversity in ankle behaviour than any other cycling activity. At BikeDynamics we have seen both strong toe down and toe up styles and a difference between maximum and minimum ankle angle ranging from 4° to 30°. There is also no clear unambiguous guidance for what we should be doing with our ankles.

Our recommendation is quite simple:

Avoid intentional or unintentional dorsiflexion on the down stroke as this will only lead to power loss and lateral knee movement. If you wish to kick your heel down, do so as you approach the top of the cycle.

Strong Plantarflexion

In this case the difference between minimum and maximum angles is 30° with very little reduction in angle as the loads are first applied.

Strong Dorsiflexion

This cyclist experienced a significant tightening of the ankle as he applied power on the downstroke. The angle only started to grow again at the bottom of the stroke but was still 4° tighter than the start point.

Normal Ankle

A small amount of ankle tightening is quite common as the ankle joint muscles respond to the loads applied by the glutes and quads. This angle is quickly recovered though and the ankle continues to grow, usually by approx. 20° to the bottom of the stroke before tightening again on the upstroke.

Pushing behind

This cyclist showed a good, growing ankle angle through the downstroke but was unusual in continuing to open the angle through most of the upstroke as well, tightening quickly in the last few degrees before top dead centre.

BikeDynamics Bibliography

You may be interested in some of the contents of the BikeDynamics library.

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Page Last Updated : 29th January 2012

BikeDynamics - Bike Fitting Specialists