BackgroundThe purpose of this investigation was to undertake a hypothesis‐generating study to identify candidate variables that characterize people with knee osteoarthritis who are most likely to experience a positive response to exercise.MethodsOne hundred and fifty participants with knee osteoarthritis participated in this observational, longitudinal study. All participants received a standard exercise intervention that consisted of 20‐min sessions two to three times a week for three months. The classification and regression tree methodology (CART) was used to develop prediction of positive clinical outcome. Positive pain and disability outcomes (dependent variables) were defined as an improvement in pain intensity by >50% or an improvement of five or more on the Oxford knee score, respectively. The predictor variables considered included age, sex, body mass index, knee osteoarthritis severity (Kellgren/Lawrence grade), pain duration, use of medication, range of knee motion, pain catastrophizing, self‐efficacy and knee self‐perception.ResultsFifty‐five participants (36.6%) were classified as responders for pain intensity and 36.6% were classified as responders for disability. The CART model identified impairments in knee self‐perception and knee osteoarthritis severity as the discriminators for pain intensity reduction following exercise. No variables predicted reduction of disability level following exercise.ConclusionsSuch findings suggest that both body perception and osteoarthritis severity may play a role in treatment outcome with exercise. It also raises the possibility that those with higher levels of disrupted body perception may need additional treatment targeted at restoring body perception prior to undertaking exercise.SignificanceRegardless age, sex, body mass index, pain duration, use of medication, knee range of motion, pain catastrophizing and self‐efficacy, participants with knee osteoarthritis who report low levels of body perception disruption (a FreKAQ score ≦ 17) and minimal structural changes (KL grade I) demonstrate significantly better outcomes from exercise therapy than other participants.

The aim of this study was to explore the existence of subgroups in a cohort of people with knee osteoarthritis (OA) based upon data from multiple pain-related variables and to profile identified clusters according to levels of pain intensity and knee-related disability. Three hundred and three people with knee OA were recruited. Latent profile analysis was used to confirm the optimal number of knee OA subgroups. Body mass index, radiographic knee OA severity, pain catastrophizing, pain related self-efficacy, and knee specific self-perception, were incorporated into the model. Cluster, demographic and clinical variables were compared between the resulting classes. Four distinct classes were identified. Cluster 1 (28.7%) represented early radiographic OA, and moderate pain intensity, disability and cognitive and perceptual dysfunction. Cluster 2 (18.8%) showed advanced radiographic OA, and moderate pain intensity, disability and cognitive and perceptual dysfunction. Cluster 3 (34.3%) represented various levels of radiographic OA, and the lowest pain intensity, disability and cognitive and perceptual dysfunction. Cluster 4 (18.1%) represented various levels of radiographic OA, the highest disability and cognitive and perceptual dysfunction. Considering cognitive factors and disturbed body perception may help to explain the phenomenon of the discrepancy between the knee-related disability and the severity of radiographic knee OA.

Introduction: There are complex interactions between pain and perceptions of the painful body part in musculoskeletal disorders, and disruption of various body representations in people with chronic pain. Objectives: The purpose of this study was to investigate how frequently people with knee osteoarthritis (OA) complain of swelling without objective evidence of swelling, and describe the clinical characteristics of this population. Methods: Forty-six people with knee OA (68.1 6 8.8 years) participated in this cross-sectional study. Subjective and objective swelling was evaluated by knee-specific body perception questionnaire and ultrasonography, respectively. Pain intensity, disability, pain-related beliefs, 2-point discrimination threshold, and quadriceps muscle strength were also evaluated.Results: Approximately 1/3 of participants (n 5 15) had subjective feelings of knee swelling in the absence of objective swelling (S only). Fifteen participants had both subjective and objective knee swelling (S 1 O group) and 16 had neither subjective nor objective knee swelling (No S/O group). Participants in the S only group had similar pain or disability as those in the S 1 O group but had more severe pain or disability than those with in the No S/O group. Those in the S only group also had larger 2-point discrimination distance threshold at the medial knee (impaired tactile acuity) than those in the S 1 O group and had more dysfunctional pain catastrophizing and pain-related self-efficacy than both other groups. Conclusion: Our results suggest that about 30% of people with knee OA perceive swelling of the knee in the absence of any objective swelling and that this is accompanied by severe pain and functional disability. Considering altered body image of the knee may reveal relevant treatment-based subgroups in people with knee OA.