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Clinical examination of the knee involves eliciting certain signs that may indicate the presence of knee pathology. One such is quadriceps wasting. This occurs most commonly as the result of disuse or from a painful or unstable lesion of the knee.
Comparing the circumference of the thighs at a set level above the patella is the standard method of testing for atrophy.1,2 This, however, assumes that the thighs are normally of equal circumference.3
It has been noted by the senior author (GCB) that, in children, the non-kicking leg seemed often to be larger than the other. We aimed to test this observation in a prospective study of a group of professional soccer players.
Patients and methods
A population of 38 players took part in the study, all from professional clubs in Edinburgh. None had a recent injury.
All the participants had both thigh circumferences measured at a point 15 cm above the proximal pole of the patella. In each case the subject was standing and the quadriceps relaxed. The trial was blinded in that the investigator making the measurements did not know which foot was predominant. To minimise error, all measurements were carried out by one investigator. The foot preference of each player was recorded on a sliding scale and later converted into a percentage. All expressed a preference for one foot over the other.
Complete data were available for 38 players. Of those with a preference for their right foot, 95% (n = 20) had a larger left thigh (range 1.5–2 cm). The difference was less striking in the group with left foot preference, with 62.5% (n = 8) having a larger right thigh (range 1.5–2 cm).
These differences were analysed using the Wilcoxon signed rank test (Minitab Release 12.21: www.minitab.com). The test showed that the differences were significant (p = 0.001) with a 95% confidence interval for the median difference in thigh circumference (non-dominant) of 0.5 to 1.0 cm.
We conclude that there is strong statistical evidence that the thigh circumference of the non-dominant leg is significantly greater than that of the dominant leg by between 0.5 and 1 cm. This supports the hypothesis that professional soccer players have larger quadriceps in their non-kicking legs.
This should be taken into account when examining the legs of sportsmen and women. There is much scope for further investigation into this trend, particularly as to whether it occurs in other sports, and at what level of participation this effect becomes apparent.
We would like to thank the players of Heart of Midlothian and Hibernian Football Clubs who kindly took part in the study.
No formal ethical approval was required for this study.
Competing interests: none declared