Criterion-related validity of a clinical measurement to determine the medial/lateral component of patellar orientation

Study Design: Repeated measures design using a sample of convenience. Objective: To assess the criterion-related validity and intrarater reliabil ity of a clinical measurement used for determining the medial/lateral posit ion of the patella. Background: Patellar taping is a common treatment for patellofemoral pain. Application of this intervention requires accurate assessment of patellar o rientation; however, the validity of this clinical procedure has not been d ocumented. Methods and Measures: Fourteen subjects (10 women, 4 men; average age, 41 /- 16 years) were evaluated. Clinical assessment of medial/lateral patellar orientation using the technique described by McConnell was compared with t he actual position of the patella as determined through magnetic resonance imaging (MRI). Imaging was done on 7 knees of 4 subjects who were asymptoma tic and 11 knees of 10 subjects who were symptomatic. Both clinical and MRI assessments were made with the subjects supine, the knee extended, and the quadriceps relaxed. Agreement between the 2 techniques and the intrarater reliability of each measurement were quantified by means of the intraclass correlation coefficient (ICC). Results: Both the clinical and MRI measures of medial/lateral patellar disp lacement were found to demonstrate good intrarater reliability (ICC = 0.91 and 0.85, respectively). The agreement between the clinical and MRI determi nations of medial/lateral patellar position was poor (ICC = 0.44). The aver age amount of lateral patellar displacement as determined by the clinical m ethod was more than twice that established through MRI. Conclusions: The clinical assessment of the medial/lateral position of the patella overestimates the true amount of lateral patellar displacement. A m ore valid clinical method of assessing the medial/lateral component of pate llar orientation is necessary.