Presented at NACOB 98: North American Congress on Biomechanics Canadian Society for Biomechanics - American Society of Biomechanics University of Waterloo Waterloo, Ontario, Canada August 14-18, 1998

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THREE-DIMENSIONAL MEASUREMENT OF Q ANGLES
WITH AND WITHOUT STANDARDIZED FOOT POSITIONS

L.A. Livingston ¹ , S.J. Spaulding ^2
1 Department of Kinesiology and Physical Education, Wilfrid Laurier University
² Faculty of Health Sciences, University of Western Ontario

INTRODUCTION

Foot position influences Q angle magnitude, yet few have standardized this aspect of their testing procedure. In this study, three-dimensional Q angle measurements were taken bilaterally, with feet positioned in self-selected versus calibrated stances. The degree of association between Q angles derived in each position was assessed.

REVIEW AND THEORY

Despite the call for standardized Q angle measurement procedures (Ando et al., 1993; Hvid & Andersen, 1982; Olerud & Berg, 1984), few have opted to control foot position, with no preferred method emerging to date. Reider and others (1981) had subjects stand with the medial borders of the feet placed together, side by side, as is prescribed in the Romberg test of balance. Guerra and coauthors (1994), in contrast, aligned the longitudinal axis of the foot perpendicular to the coronal plane of the body. In another study, subjects stood with heels spaced 7.5 cm apart and the medial borders of the feet 60° divergent (Cowan et al., 1996). The lack of consistency in the foot positions adopted continues to make comparative interpretation difficult. Little is known, moreover, as to the extent to which constraining the feet in a position other than a preferred stance affects the resulting Q angle measurement.

In a recent study, preferred foot placement position was observed in 262 adults (McIlroy & Maki, 1997). The mean stance position was found to be 0.17 m between heel centres, with an angle of 14° between the long axes of the feet. This position clearly differs from those used in previous Q angle studies. Therefore, the purpose of this investigation was to compare the magnitude of bilateral Q angle measurements in self-selected versus standardized foot positions. The null hypothesis was that there would be no significant differences in Q angles measured under differing foot positions.

PROCEDURES

Twenty young adult males (n=6) and females (n=14), ranging in age from 19 to 30 years (M=22.1, SD=3.5), volunteered to participate. Individuals with a history of acute injuries to, or chronic dysfunction of, the lower limb were excluded from the study.

Right and left Q angles were defined by placing infrared LEDs bilaterally on the anterior superior iliac spines, midpoints of the patellae, and the center of the tibial tubercles. Three-dimensional coordinates were gathered using an OPTOTRAK motion measurement system (Northern Digital, Waterloo, Canada). Five data collection trials were completed while subjects adopted a static standing position and each of the following three foot positions: self-selected, medial borders of the feet touching (Romberg position), and 0.17 m between heel centres, with an angle of 14° between the long axes of the feet (mean stance position).

Data were analyzed using a mixed between-within repeated measures ANOVA procedure. Pearson correlation coefficients were generated to assess the degree of association between measures derived under the three measurement conditions.

RESULTS

Descriptive statistics for the Q angle by foot position, and by limb, are presented in Table 1. Significant differences in mean Q angle magnitude between foot positions (F(2,38)= 34.09, p<.001) and between limbs (F(1,19)=4.14, p<.05) were observed. Q angles differed significantly between all three stance conditions. Significant interaction effects were not observed. The descriptive and correlational analyses (Table 2) reveal that mean Q angle measurements taken in conjunction with the Romberg foot position most closely resemble those gathered under self-selected stance conditions.

Foot Position	Left Q Angle (°)	Right Q Angle (°)
Self- Selected Position M (SD) Median Maximum Minimum	11.4 (7.2) 11.4 22.8 -1.8	14.4 (6.5) 15.4 26.3 1.1
Romberg Position M (SD) Median Maximum Minimum	12.7 (7.7) 11.1 28.0 1.4	16.1 (6.2) 15.6 26.8 3.9
Mean Stance Position M (SD) Median Maximum Minimum	7.2 (7.8) 3.9 24.7 -3.0	11.0 (6.4) 10.4 24.2 1.8

Table 1. Mean Q angle values by foot position and limb.

	Self-Selected Position Left Limb	Self-Selected Position Right Limb
Romberg Position	0.92	0.86
Mean Stance Position	0.93	0.82

Table 2. Pearson product-moment correlation coefficients between Q angle measures. All correlations are significant at the p<.001 level.

DISCUSSION

These results are in agreement with Olerud and Berg's (1984) finding that the mean Q angle increases or decreases as the foot rotates internally or externally, respectively. Measured values of the Q angle in the right and left leg were greater for all subjects when measured in the feet together as opposed to the mean stance position. However, in contrast to Olerud and Berg's (1984) study, we observed much smaller changes in mean Q angle magnitude with alterations in foot position. This difference is accounted for by our use of less extreme, yet more ecologically-valid, foot positions. The use of a three-dimensional measurement system in this investigation, moreover, eliminated the systematic measurement error of the two-dimensional photographic technique utilized by the aforementioned authors.

In comparison to the self-selected stance position, placing the feet together increased the varus angle of the quadriceps ray and decreased the valgus angle of the patellar tendon ray, resulting in a significantly larger Q angle. The mean stance position, in contrast, led to decreased valgus and varus angles of the patellar and quadriceps rays, respectively, and a significant decrease in the Q angle. For most, the mean stance position required greater external foot rotation than the self-selected stance. These trends were observed in both limbs.

Correlational analysis suggests that measurements of the right Q angle in the two calibrated stances yield reasonable estimates (r²=85-87%) of that in a self-selected stance position, while measures of the left Q angle are less predictive (r²=67-74%). The summarized data clearly demonstrate, however, that measurements taken with feet side by side yield mean values more closely resembling those found under self-selected stance conditions. Significant differences in side to side Q angle measures, as was observed in this study, have been previously documented (Hahn & Foldspang, 1997). Even with such asymmetry, the mechanism whereby the Q angle increases and decreases with foot rotation remains the same in each limb.

REFERENCES

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Cowan D. et al. Med Sci Sports Exerc, 28, 945-952, 1996.

Guerra J. et al. JOSPT, 19, 200-204, 1994.

Hahn T. et al. Scand J Med Sci Sports, 7, 43-48, 1997.

Hvid I. et al. Acta Orthop Scand, 53, 577-579, 1982.

McIlroy W. et al. Clin Biomech, 12, 66-70, 1997.

Olerud C. et al. Clin Orthop, 191, 162-165, 1984.

Reider B. et al. Am J Sports Med, 9, 270-273, 1981.