Abstract
Quadriceps angle (Q-angle) has been used to reflect the extent of genu valgum and may have implications for activity selection, training considerations, and/or potential medical interventions. Q-angle evaluation must be stable and sufficiently precise in adults if it is to have clinical and/or research utility. PURPOSE: To establish the stability reliability, precision, and minimum difference needed to represent a change in Q-angles obtained using surface goniometry. METHODS: Q-angle was assessed for 25 men and 27 women with surface goniometry on two separate occasions separated by 48 hours. Well-rested subjects assumed a supine position with: 1) extended hips and knees, 2) a neutral hip rotational position, 3) a neutral foot position, and 4) a contracted quadriceps femoris muscle. The axis of a manual goniometer was placed over the center of the right patella with the fixed arm situated over the anterior-superior iliac spine and the mobile arm over the center of the tibial tuberosity. Stability reliability was calculated using intraclass correlation (ICC, 2-way random) and precision by standard error of measurement (SEM). 95% limits of agreement (LOA) was also calculated to estimate the magnitude of difference needed to represent actual change. Acceptable ICC's were set at > or =0.70 for reliability. RESULTS: The following ICC (SEM) were found: all subjects = 0.88 (1.0 deg), men = 0.77 (1.0 deg), women = 0.85 (1.0 deg) (See Table 1). CONCLUSION: The surface goniometry protocol described herein was reliable for all subjects, men only, and women only. Although precision also appeared to be reasonable, a minimum difference of three degrees would be needed to represent a change or difference in Q-angles. Table 1. Q-angle based on surface goniometry. (ProQuest: ... denotes formulae and/or non-USASCII text omitted)