AMERICAN SOCIETY OF BIOMECHANICS
Presented at the Twenty-First Annual Meeting
of the American Society of Biomechanics
Clemson University, South Carolina
September 24-27, 1997
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| AMERICAN SOCIETY OF BIOMECHANICS
Presented at the Twenty-First Annual Meeting |
Investigators have traditionally adopted between-group analysis-of-variance (ANOVA) designs to test for differences in quadriceps (or Q) angle magnitude between those asymptomatic versus symptomatic for anterior knee pain (AKPS). Few (Hvid et al., 1982; Messier et al., 1991), in contrast, have tested for bilateral (ie, right versus left) within-subject lower limb differences. In this study, goniometric measurements of right and left Q angles were compared between-groups (ie, asymptomatic, unilateral symptomatic, bilateral symptomatic) and within-groups (ie, right versus left lower limb).
An excessive Q angle (ie, >15-20°) is commonly viewed as anatomic risk factor in the etiology of overuse injuries of the knee (Cowan et al., 1996). However, it is now considered to be a less reliable clinical measure than was previously believed (Woodall et al., 1990). The inability of researchers to consistently link excessive Q angles with the occurrence of AKPS is to blame. Methodological differences (eg, measurements drawn in supine versus weight-bearing positions) may account for some of the observed discrepancies in reported Q angle values, but so too may the tendency for investigators (Cowan et al., 1989; Woodland et al., 1992) to derive Q angle measures from only one lower limb. In one study, right and left Q angle values were combined into one sample for the purposes of subsequent analysis (Caylor et al., 1993). These approaches are problematic for they imply that Q angles are bilaterally symmetric, an assumption that does not appear to have been thoroughly examined.
A review of the literature revealed only two investigations (Hvid et al., 1982; Messier et al., 1991) in which Q angles were measured and reported bilaterally. While no significant right to left limb differences were reported, the generalizability of the results are limited by the small sample sizes that were utilized.
The purpose of this investigation, therefore, was to compare measured values of the left and right Q angles to examine whether bilateral similarities or differences existed between a group of asymptomatic controls and those symptomatic for anterior knee pain syndromes. The null hypotheses were that there would be no significant between-group (ie, asymptomatic, unilateral AKPS, bilateral AKPS) or within- subject (ie, right vs left limb) differences, or interaction effects.
Seventy-five young-adult males (n=36) and females (n=39), ranging in age from 15 to 48 years (M=26.1, SD=7.2), volunteered to participate in this study. After completing a general information and an AKPS screening questionnaire, they were assigned to one of three groups: asymptomatic control (n=50), unilateral knee pain sufferers (n=11), or bilateral knee pain sufferers (n=14).
Goniometric measurements were taken with the subjects in a standing position and the knees in full extension. Q angles were measured bilaterally using the standard clinical method of measurement (Horton et al., 1989). A universal goniometer was used to measure the Q angle with the anterior superior iliac spine, midpoint of the patella, and the center of the tibial tubercle as landmarks. All measurements for a given subject were taken by the same investigator. Intertester reliability was established in a preliminary study by measuring the right Q angle in a group of 14 subjects. An r=0.67 (ICC (2,1)) (Shrout et al., 1979) determined that intertester reliability was good (Fleiss, 1986).
The data were analyzed using a mixed between-within multi-way ANOVA procedure. The dependent variable was Q angle magnitude while the independent variables included group, gender, and lower limb. The data were also reviewed on a case-by-case basis.
Descriptive statistics for the Q angle by group and by limb are presented in Table 1. A significant difference in Q angle magnitude between groups (F(2,138)=3.34, p=0.04) was observed, as was a significant group by limb interaction effect (F(2,138)=2.99, p=0.05). Significant differences in Q angle by gender (p=0.62) and limb (p=0.33) were not observed. Forty-seven percent of all the subjects studied demonstrated a minimum 4° difference in Q angle values between the right and left lower limb, while 17% displayed bilateral differences of 8° or more.
| Group | Left Q Angle (degrees) | Right Q Angle (degrees) |
|---|---|---|
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Control (n=50) M (SD) Maximum Minimum | 11.3 (5.5) 23.0 0.7 | 10.0 (4.4) 21.0 1.0 |
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Unilateral (n=11) M (SD) Maximum Minimum | 12.5 (6.6) 21.7 3.3 | 12.8 (6.0) 19.0 0.3 |
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Bilateral (n=14) M (SD) Maximum Minimum | 11.4 (5.3) 23.7 0.7 | 15.7 (7.2) 30.0 3.3 |
Table 1. Mean Q angle values by group and limb.
A lack of comparable investigations (ie, in terms of the subject groups studied and the measurement methodologies utilized) prevents comparisons between the results reported herein and those of previous investigations. The findings do suggest, however, that the assumption of bilateral symmetry in Q angle values may be erroneous. While mean left lower limb Q angle values varied little more than 1° between the control and symptomatic groups, the mean right Q angle values differed by up to 5.7° between the asymptomatic and bilateral AKPS sufferers. Moderate (ie, 4°) to substantial (ie, 8°) amounts of bilateral asymmetry in Q angle values were also observed when cases were viewed on an individual basis.
The presence of an interaction effect provides some evidence that the magnitude of the left and right Q angles, as well as the degree of asymmetry between them, needs to be considered when attempting to link the occurrence of AKPS to the Q angle measure. In order to validate this speculation, more research utilizing large sample sizes (ie, larger than even that utilized in this investigation) and the bilateral measurement approach is required.
Caylor et al. JOSPT, 17, 11-16, 1993.
Cowan et al. Med Sci Sports Exerc, 28, 945- 952, 1996.
Fleiss, J.L. Reliability of Measurement, 1-12, Wiley, 1986.
Horton et al. Phys Ther, 69, 897-901, 1989.
Hvid et al. Acta Orthop Scand, 53, 577-579, 1982.
Hvid et al. Acta Orthop Scand, 52, 661-666, 1981.
Messier et al. Med Sci Sports Exerc, 23, 1008- 1015, 1991.
Shrout et al. Psych Bull, 86, 420-428, 1979.
Woodall et al. J Orthop Sports Phys Ther, 11, 535-542, 1990.
Woodland et al. Am J Sports Med, 20, 208- 211, 1992.
The authors gratefully acknowledge that financial support for this research was received from a grant provided by WLU operating funds.