Are there three main subgroups within the patellofemoral pain population? A detailed characterisation study of 127 patients to help develop targeted intervention (TIPPs)

Abstract

BackgroundCurrent multimodal approaches for the management of non-specific patellofemoral pain are not optimal, however, targeted intervention for subgroups could improve patient outcomes. This study explores whether subgrouping of non-specific patellofemoral pain patients, using a series of low cost simple clinical tests, is possible.MethodThe exclusivity and clinical importance of potential subgroups was assessed by applying à priori test thresholds (1 SD) from seven clinical tests in a sample of adult patients with non-specific patellofemoral pain. Hierarchical clustering and latent profile analysis, were used to gain additional insights into subgroups using data from the same clinical tests.Results130 participants were recruited, 127 had complete data: 84 (66%) female, mean age 26 years (SD 5.7) and mean body mass index 25.4 (SD 5.83), median (IQR) time between onset of pain and assessment was 24 (7–60) months. Potential subgroups defined by the à priori test thresholds were not mutually exclusive and patients frequently fell into multiple subgroups. Using hierarchical clustering and latent profile analysis three subgroups were identified using 6 of the 7 clinical tests. These subgroups were given the following nomenclature: (1) ‘strong’, (2) ‘weak and tighter’ and (3) ‘weak and pronated foot’.ConclusionsWe conclude that three subgroups of patellofemoral patients may exist based on the results of six clinical tests which are feasible to perform in routine clinical practice. Further research is needed to validate these findings in other data sets and, if supported by external validation, to see if targeted interventions for these subgroups improve patient outcomes.

The Validity of the Modified Star Excursion Balance Test as a Predictor of Knee Extensor and Hip Abductor Strength

“…Whilst both used healthy subjects Katoh et al [15] did not report the participants as athletic and this could explain the higher scores in this study. However, in contrast, Selfe et al [2] reported higher scores in a PFP patient population for the strong male subgroup (age >30; comparable to this study) which could support the theory that this subgroup of PFP patients have overload of the knee as a possible cause of pain.…”

“…To allow for dropouts a total of 20 were recruited into the study. Using a purposive sample of healthy male runners in the 18-39 age range ensured there was good ecological validity with the strong and physically active PFP subgroup as identified by Selfe et al [2]. All participants met this inclusion criteria with running at least once per week set as an acceptable frequency for physical activity.…”

“…For the isometric strength tests the HHD was mounted against a stabilisation strap as described in detail in previous studies [2,3,20,21]. For knee extension the participant was seated on a plinth ( Figure 1) and for hip abduction they were in a side lying position difference between limb dominance in any of the measures the data were combined to further increase the power of the data set (n = 36).…”

“…Subsequently, three subgroups have been identified by Selfe et al [2]. Maximal isometric knee extension (quadriceps) and hip abduction (gluteal) strength, tested using a hand held dynamometer (HHD), was an important factor in defining the subgroups.…”

“…However, anecdotal clinician feedback from Selfe et al [2] suggested that the use of a HHD muscle strength test, although acceptable for research purposes, is regarded as expensive and impractical in routine clinical practice.…”