Adjustment of the bicycle:

A saddle adjusted at the wrong height can injure the knees, particularly where the kneecap (patella) and the upper leg (femur) make contact. A saddle which is adjusted too high results in a force that moves the kneecap laterally. In the stretching phase of the knee, the kneecap is pushed aside laterally and eventually results in pain at the outer side of the kneecap. This phenomenon is reinforced by the position of the legs. A saddle which is adjusted too low leads to a position in which the legs are bent too much, which might result in straining of the kneecap and upper leg. If the saddle is positioned too much forward (steep seat angle), the angle in the knee joint will be too small which will have the same effect as when the saddle is adjusted too low.

The longitudinal positioning of the foot (shoe) influences the efficiency of the cycling movement. The sideward (lateral) adjustment is not only dependent on the natural position of the feet, but mainly on the imposed pattern of the cycling movement. To put it differently: the position of the foot on the pedal must be such that the imaginary line of force runs from the upper leg to the lower leg, right across the middle of the knee. Effectively, this means that the inner side of the foot runs parallel to the circle that is made by the pedal. If the shoe cleats are turned inward, the heels are turned outward. This often happens when the cyclist moves his ankles too close to the cranks. Cycling in this position can lead to knee complaints and knee injuries because the upper leg and lower leg are twisted and not in line. Exceptions are those cyclists whose feet show a natural inward position. The shoe cleats of these cyclists can be placed in such a position that the heels point slightly outward.
For the adjustment of the shoe cleats also see Shoe Cleat Adjuster. Shoe Cleat Adjuster.

Physical causes:

The valgus and varus position of the front part of the foot results in supination or pronation during the process of cycling. This implies that the knee is no longer in a line-of-force position of the upper leg and the lower leg and deviates laterally from the ideal line. This leads to lateral pressure on the knee with an increased risk of knee injuries and loss of energy. According to a study conducted by Garbalosa, in 1994, 87% of the people examined had a varus position of the front part of the foot, 9% had a valgus position, and 4% had a neutral position. According to Stevens (1998), 31% of 100 cyclists examined had an unfavorable outlining of the front part of the foot. The position of the front part of the foot can be corrected by using an orthopedic in-sole, or use of the American Big Meat wedge. The drawing, on the right, illustrates the effect of a varus position of the front part of the foot and the effect of the correction on the lateral position of the knee. It should be noted that this wedge is not placed right under the front part of the foot but in between the shoe cleat and the sole of the shoe. The manufacturer has also conducted a survey into the effect of the Big Meat on the output of the cyclist. This survey shows an increase in power-output by an average of 1.9% (Reuter, 1997).

In case of a difference in length of the legs, there is usually more pressure on the shorter leg than on the longer leg. As a result of the imposed movement of cycling, the difference in length must be corrected; this is done by pushing the longer leg in an outward direction during the cycling process in order to compensate the difference in length. Consequently, the knee does not remain in a line-of-force position and the pressure on this knee will not be equally intensive. As a result, this type of cyclist shows an asymmetric development of the muscles. The upper leg of the shorter leg is developed more strongly, and this asymmetry runs diagonally through the entire moving system of the body because the lower leg of the longer leg is stronger. This asymmetric cycling cycle often leads to straining, which manifests itself in knee injuries of the shorter leg. Often the type of cyclist who has this deviation also suffers from pain in the lower back because he does not adopt an upright position on his bicycle.

By contrast, the longer leg sometimes endures more pressure, as well. This type of cyclist unconsciously corrects the difference in length of the legs from his back. He manages to maintain an upright position on his bicycle, but he is only able to exercise power through his longer leg because, otherwise, he will end up in a lopsided position. The diagonal asymmetry is opposite to the type of cyclist mentioned earlier and results in complaints of the knee of the longer leg. Cyclists with O-shaped or X-shaped legs face the problem of the line in force which does not run straight across the knees, which could also result in increased complaints of the knees. These complaints can partly be overcome/prevented by opting for a shoe and pedal system in which the front part of the foot maintains a certain lateral latitude and/or by using orthopedic arch support.