How useful is a single measurement of patellar mobility in the assessment of patients with patellofemoral pain?

Introduction: Patellar mobility is often routinely assessed in people with patellofemoral pain (PFP) in clinical practice. This study assessed the stability of the data when measuring patellar mobility using the total medial-lateral patellar glide test across multiple repetitions. It also compared patellar mobility of people with healthy knees to people with PFP and within subgroups of PFP. Methods: Twenty-two people without knee problems underwent five repetitions of the total medial-lateral patellar glide test. Differences in mean value for each repetition and the intra-class correlations (ICC) between the first assessment and the average values of additional repetitions were calculated. Mean patellar mobility was compared with 127 participants with PFP who took part in a previously published subgrouping study. Differences between the healthy knee group and PFP subgroups were also explored using a one-way ANOVA with pairwise comparisons. Results: The mean patellar mobility in healthy individuals was 16.4 mm (SD 5.3), difference in mean patellar mobility across repetitions was minimal and the ICC ranged between 0.93 and 0.95. People with PFP had significantly lower patellar mobility than the healthy knee group. Two of three PFP subgroups had statistically significantly lower mean patellar mobility (difference in mean -5.6mm and -6.5mm; P<0.001). Discussion: A single medial-lateral patellar glide test appears as informative as repeated tests in practice. One off measures of patellar mobility using the total medial-lateral patellar glide test may identify subgroups of PFP to help guide treatment in clinical practice. Further work is needed to assess other reliability parameters for this measure.