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Baseline pressure-pain tolerance threshold predicts the clinical outcome of a weight loss intervention in obese knee OA patients: a prospective cohort study

2012; Elsevier BV; Volume: 20; Linguagem: Inglês

10.1016/j.joca.2012.02.425

1522-9653

Tanja Schjødt Jørgensen, Marius Henriksen, René dePont Christensen, Thomas Graven‐Nielsen, Henning Bliddal, Anders Jespersen,

Pain Mechanisms and Treatments

Purpose: Knee osteoarthritis (OA) is a chronic pain condition, often associated with peripheral and central sensitization of the nociceptive system. Obesity is strongly linked with knee OA and weight-loss interventions are generally effective in relief of knee OA symptoms. However, it is unknown if sensitization may restrain improvement in pain. The aim of the study was to investigate whether baseline pressure-pain sensitivity of the lower leg can predict the clinical outcome of a dietary intervention in obese knee OA patients, which could support clinical decision on how to deliver dietetic support in terms of prioritizing efforts. Methods: Participants of this prediction study (the CAROT study) included 168 obese (88% of the CAROT cohort) patients with symptomatic knee OA according to the ACR criteria. The patients completed a dietary intervention, and had a computerized tourniquet cuff pressure algometer assessment at baseline - assessing pressure-pain sensitivity of the lower leg. During cuff inflation patients rated the pressure-pain intensity continuously on an electronic visual analogue scale (VAS), with 0 indicating "no pain" and 10 defined "worst pain imaginable". The patients pressed a button, when the pressure-pain intensity was intolerable (pain tolerance threshold, PTT recorded in kPa) and the corresponding VAS score defined the pressure-pain limit (PTL). The PTT and PTL were measured before a 16-week intensive dietary intervention resulting in a significant weight loss. Treatment response was defined according to the Outcomes Measures in Rheumatology Clinical Trials and Osteoarthritis Research Society International (OMERACT-OARSI) responder criterion (yes/no). The associations between baseline PTT and PTL and lack of clinical response according to the OMERACT-OARSI criterion - despite receiving intensive dietary therapy - were assessed using logistic regression analysis; adjustments for potential confounding factors (gender, age, radiographic disease severity and baseline BMI) were performed. Results: Baseline PTT was associated with lack of response to weight loss according to the OMERACT-OARSI responder criteria, showing that patients with higher PTT had lower odds of non-response (odds ratio = 0.966; 95% confidence interval (CI) 0.94 - 0.99, P = 0.0066) implying a better prognosis. There was no association between baseline PTL and treatment response (odds ratio = 0.998; 95% confidence interval (CI) 0.85 - 1.17, P = 0.9761). Conclusions: This study indicates that obese knee OA patients with low pressure pain tolerance (i.e. high sensitivity) at baseline have a reduced likelihood of symptomatic response to a weight loss intervention as compared to patients with high pressure pain tolerance (i.e. low sensitivity). Central sensitization of the nociceptive system may explain the relative high pressure pain sensitivity in the patients responding less efficient to the weight loss. Pain sensitivity assessment may aid clinical decision making as a prognostic tool.