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.
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.