Background & Aims
Movement-evoked pain (MEP) represents the primary symptom of knee osteoarthritis (KOA), occurring during weight-bearing movements. Decreased bone mineral density (BMD) has been identified as a risk factor associated with the progression of KOA severity, while joint inflammation, as assessed through magnetic resonance imaging (MRI) detecting synovitis and bone marrow lesions (BML), is also recognized as a precipitating factor for pain. Additionally, previous studies employing quantitative sensory testing (QST) have indicated that the extent of pain sensitization correlates with pain severity and poor prognosis. However, the etiology of MEP in KOA, whether attributable to joint structural changes or pain sensitization, remains poorly understood. This study aimed to investigate the respective contributions of structural abnormalities and pain sensitization in elucidating the mechanisms underlying MEP in patients with KOA.
Methods
Patients underwent assessments for demographic data (age, sex, and body mass index [BMI]), KOA severity, BMD in the femoral neck measured by dual-energy X-ray absorptiometry, Hoffa synovitis and bone marrow lesions using the Whole-Organ Magnetic Resonance Imaging Score (WORMS). Pressure pain threshold (PPT) was measured at the knee and forearm, along with assessments of temporal summation of pain (TSP) at the knee, and MEP. For the measurement of MEP, knee joint pain was scored using a numerical rating scale (NRS, 0 to 10) before and every minute during a 6-minute walking test (6MWT). The MEP index was defined as the change in the NRS score from baseline to the sixth minute of walking. Data analysis was conducted in two steps. First, to assess changes in MEP, Friedman analysis of variance (ANOVA) with time was used to examine the increase in the NRS during the 6MWT. Second, hierarchical linear regression analysis was performed to examine the factors associated with the MEP index.
Results
The study included a total of 92 patients. Analysis using Friedman ANOVA revealed statistically significant increases in NRS with each minute (P < 0.001). The MEP index significantly correlated with WORMS-Hoffa synovitis, PPT at the knee and forearm, and TSP at the knee but not with KOA severity, WORMS-BML and BMD. All underlying assumptions for linear regression, including the assumption of linear relationships, homoscedasticity, independency, and normality of residuals, were appropriately met. In hierarchical linear regression analysis, WORMS-Hoffa synovitis, PPT at the forearm, and TSP at the knee were significantly associated with the MEP index (P < 0.001). All tolerances were > 0.1, and all variance inflation factors were < 10, indicating that multicollinearity did not occur.
Conclusions
MEP increased statistically significantly every minute during walking, suggesting the presence of subgroups of patients with increased MEP. Additionally, hierarchical linear regression analysis revealed associations between synovitis and pain sensitization with the MEP index. These findings suggest that both peripheral and central mechanisms contribute to the development of MEP in KOA, which may aid in identifying potential targets for treatment and predicting the risk of exercise-induced hyperalgesia before treatment.
References
1) Corbett DB, Simon CB, Manini TM, George SZ, Riley JL 3rd, Fillingim RB. Movement-evoked pain: transforming the way we understand and measure pain. Pain. 2019;160(4):757-761.
2) Wideman TH, Finan PH, Edwards RR, Quartana PJ, Buenaver LF, Haythornthwaite JA, Smith MT. Increased sensitivity to physical activity among individuals with knee osteoarthritis: relation to pain outcomes, psychological factors, and responses to quantitative sensory testing. Pain. 155(4):703-711.
3) Vaegter HB, Petersen KK, Sjodsholm LV, Schou P, Andersen MB, Graven-Nielsen T. Impaired exercise-induced hypoalgesia in individuals reporting an increase in low back pain during acute exercise. Eur J Pain. 2021;25(5):1053-1063.
4) Neogi T, Guermazi A, Roemer F, et al. Association of Joint Inflammation With Pain Sensitization in Knee Osteoarthritis: The Multicenter Osteoarthritis Study. Arthritis Rheumatol. 2016;68(3):654-661.
Presenting Author
Takafumi Hattori
Poster Authors
Topics
- Joint Pain