Human Studies

Epidemiological studies suggest that women are not only at a higher risk for developing knee osteoarthritis (KOA), but also report greater symptom severity compared to men. One potential underlying mechanism of these sex differences may be exaggerated inflammatory responses to pain among women compared to men. The present study examined sex differences in interleukin-6 (IL-6) response over time following experimental pain testing. We hypothesized that women, when compared to men, would show greater IL-6 reactivity when exposed to acute pain in a human laboratory setting. Eighty-four participants (36 men and 48 women) with KOA scheduled for total knee arthroplasty underwent a quantitative sensory testing (QST) battery. A total of seven IL-6 measurements were taken, twice at baseline, once immediately after QST, and every 30 minutes up to 2 hours after QST. Consistent with our hypothesis, women, when compared to men, showed accelerated increases in IL-6 levels following laboratory-evoked pain, even after controlling for body mass index, marital status, clinical pain, evoked pain sensitivity, and situational pain catastrophizing. Given that KOA is a chronic condition, and individuals with KOA frequently experience pain, these sex differences in IL-6 reactivity may contribute to the maintenance and/or exacerbation of KOA symptoms. PERSPECTIVES: The present study demonstrates that women, when compared to men, exhibit greater IL-6 reactivity after exposure to laboratory-evoked pain. Such sex differences may explain the mechanisms underlying women's higher chronic pain risk and pain perception, as well as provide further insight in developing personalized pain interventions.

Pain sensitization in knee osteoarthritis is associated with greater symptom severity and poorer clinical outcomes. Measures which identify pain sensitization and are accessible to use in clinical practice have been suggested to enable more targeted treatments. This merits further investigation. This study examines the relationship between Quantitative Sensory Testing (QST) and clinical measures of pain sensitization in people with knee osteoarthritis.

Musculoskeletal (MSK) pain is frequently reported among adolescents and children and a common reason for consultation in primary care. Our aim is to examine its prevalence in 6-year old children in a general population and to assess associations with physical and psychosocial factors. Data from the Generation R Study, a population based cohort, was used. Prevalence and characteristics of MSK pain were assessed with parent-reported questionnaires at 6-years of age (N=6200). Demographics and data on physical activity, sedentary behaviors, previous reported MSK pain and behavioral problems were extracted from questionnaires. The BMI SD score was calculated from objectively measured weight and height. A three-month prevalence of 10.0% was found for MSK pain in children, of which one third was chronic, and 44.6% experienced together with pain at other sites. Univariate analyses showed that boys and children with lower socioeconomic status (SES) reported MSK pain more frequent compared to other pain and no pain. While no associations were found between MSK pain and children's BMI and physical activity level, children with MSK pain were more likely to watch television ≥2 hours/day. Multivariable analysis showed significant associations for MSK pain at 3 years of age (OR 5.10, 95% CI 3.25 to 7.98) and behavioral problems (OR 2.10, 95% CI 1.19 to 3.72) with the presence of MSK pain. So, MSK pain is already common in young children and is often chronic or recurrent. Previous reported MSK pain and behavioral problems are independently associated with MSK pain in the studied population.

Sensory dysfunction is a common consequence of many forms of neurological injury, including stroke and nerve damage. Rehabilitative paradigms that incorporate sensory retraining can provide modest benefits, but the majority of patients are left with lasting sensory loss. We have developed a novel strategy that uses closed-loop vagus nerve stimulation (VNS) paired with tactile rehabilitation to enhance synaptic plasticity and facilitate recovery of sensory function.

The purpose of the study was to explore clinical management for new cases of musculoskeletal pain that are likely chronic. We used data from the National Ambulatory Medical Care Survey, 2007-2015, identifying visits with a new chronic musculoskeletal pain condition using pre-determined ICD-9 codes. We documented prescribing of non-opioid pain medication, opioids, physical therapy (PT), counseling, and other nonpharmacologic treatments and explored associations between patient and provider factors for each of these treatments. There were 111,994 visits over the 9-year period for a new case of chronic musculoskeletal pain, representing an average of 36.8 million weighted visits per year or approximately 11.8% of the population. Proportions that were prescribed nonopioid medication, opioids, PT, counseling and other nonpharmacologic treatments were: 40.2, 21.5, 10.0, 15.2 and 14.3 respectively. Patient age was associated with type of treatment with a young to old gradient for other nonpharmacologic treatments, PT, opioids, counseling and other medications. Orthopedists were less likely to prescribe pharmacological treatments than family practice physicians and more likely to prescribe PT. Physicians who used the electronic medical record were more likely to prescribe opioids. Contrary to practice guidelines for managing musculoskeletal pain, many patients are prescribed opioids for a new chronic musculoskeletal problem. PERSPECTIVE: We outlined in a representative sample of Americans what treatments are being prescribed for new cases of likely chronic musculoskeletal pain. Opioid prescription was double that of physical therapy. Using the electronic medical record was associated with more opioid prescription- a novel finding that should be corroborated by future research.