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 reliability of a clinical measurement used for determining the medial/lateral position of the patella.

BACKGROUND: Patellar taping is a common treatment for patellofemoral pain. Application of this intervention requires accurate assessment of patellar orientation; however, the validity of this clinical procedure has not been documented.

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 the actual position of the patella as determined through magnetic resonance imaging (MRI). Imaging was done on 7 knees of 4 subjects who were asymptomatic 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 displacement were found to demonstrate good intrarater reliability (ICC = 0.91 and 0.85, respectively). The agreement between the clinical and MRI determinations of medial/lateral patellar position was poor (ICC = 0.44). The average amount of lateral patellar displacement as determined by the clinical method 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 more valid clinical method of assessing the medial/lateral component of patellar orientation is necessary.