Distinct patterns of variation in the distribution of knee pain

Shellie A Boudreau,Albert Cid Royo,Thomas Graven-Nielsen,Mark Matthews,Kristian Thorborg,Greg Slabaugh,Michael Skovdal Rathleff,Bill Vicenzino,Ernest N Kamavuako

doi:10.1038/s41598-018-34950-2

Abstract

The patient’s expression of pain using digital-body maps expands analytic opportunities for exploring the spatial variation of bodily pain. A common knee pain condition in adolescents and adults is patellofemoral pain (PFP) and recently PFP was shown to be characterized by a heterogeneous distribution of pain. Whether there are important patterns in these distributions remains unclear. This pioneering study assesses the spatial variation of pain using principal component analysis and a clustering approach. Detailed digital-body maps of knee pain were drawn by 299 PFP patients of mixed sex, age, and pain severity. Three pain distribution patterns emerged resembling an Anchor, Hook, and an Ovate shape on and around the patella. The variations in pain distribution were independent of sex, age, and pain intensity. Bilateral pain associated with a longer duration of pain and the majority characterized by the Hook and Ovate pain distributions. Bilateral and/or symmetrical pain between the left and right knees may represent symptoms associated with longstanding PFP. The distinct patterns of pain location and area suggest specific underlying structures cannot be ruled out as important drivers, although central neuronal mechanisms possibly exemplified by the symmetrical representation of pain may play a role in individuals with longstanding symptoms.

Highlights

The possibility for patients to digitally express where they experience pain expands the analytic opportunities for understanding the spatial variation and distribution of their pain experience
The top six principal components (PCs) explained 49.7% of the pain map variation, with PC1 = 28.0%, PC2 = 6.8%, PC3 = 5.1%, PC4 = 4.2%, PC5 = 3.0%, and PC6 = 2.6% and characterize the major differences in pain images across the dataset. Both PC1 and PC2 are distinctly higher and the remaining PCs begin to plateau, thereafter these two PCs were chosen to include in the analyses
Despite the high prevalence of patellofemoral pain (PFP), little is known about the underlying PFP pathology and it is tempting to speculate if these findings hint at specific structures being affected

Summary

Introduction

The possibility for patients to digitally express where they experience pain expands the analytic opportunities for understanding the spatial variation and distribution of their pain experience. The distribution of patellofemoral pain (PFP), one of the most common knee pain presentations, is traditionally described as pain centrally (central patellar) or around (peripatellar) the patella. The purpose of this study was to explore and identify patterns in the spatial variation of pain distribution as drawn by patients with PFP on a digital body chart of the knee. Secondary aims consisted of exploring the relationship between patterns of variation in pain distribution and pain duration, pain intensity, laterality (bilateral vs unilateral) and pain symmetry in those with bilateral pain. Other factors such as age and sex were investigated as explanatory variables for both aims

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Conclusion