For decades, multiple attempts to fully understand knee osteoarthritis pathophysiology and natural history have been attempted. Despite the extensive amount of research regarding this topic, there are still marked controversies. This multifactorial condition gets influenced by local, systemic, and external factors and its progression and/or response to treatments widely varies from patient to patient. Multiple therapies have been studied in the past, low impact physical activity seems to be supported by all the current medical societies while other interventions have shown conflicting findings. Newer therapies and routes of administration are under investigation and some of them have shown promising preliminary reports. This review intends to give an overview of the current knowledge of pathophysiology and non-surgical therapies available for knee osteoarthritis.

Objective This review summarizes the scientific literature relating to the use of quantitative sensory testing (QST) for mechanism-based pain management. Design A literature search was undertaken using PubMed and search terms including quantitative sensory testing, pain, chronic pain, response to treatment, outcome measure. Settings and Patients Studies including QST in healthy individuals and those with painful disorders were reviewed. Measures Publications reported on QST methodological issues including associations among measures and reliability. We also included publications on the use of QST measures in case-control studies, their associations with biopsychosocial mechanisms, QST measures predicting clinical pain as well as predicting and reflecting treatment responses. Results Although evidence suggests that QST may be useful in a mechanism-based classification of pain, there are gaps in our current understanding that need to be addressed including making QST more applicable in clinical settings. There is a need for developing shorter QST protocols that are clinically predictive of various pain subtypes and treatment responses without requiring expensive equipment. Future studies are needed examining the clinical predictive value of QST including sensitivity and specificity for pain classification or outcome prediction. These findings could enable third-party payers’ reimbursement, which would facilitate clinical implementation of QST. Conclusions With some developments, QST could become a cost-effective and clinically useful component of pain assessment and diagnosis, which can further our progress toward the goal of mechanism-based personalized pain management.

The concept of ‘Successful Aging’ has long intrigued the scientific community. Despite this long-standing interest, a consensus definition has proven to be a difficult task, due to the inherent challenge involved in defining such a complex, multi-dimensional phenomenon. The lack of a clear set of defining characteristics for the construct of successful aging has made comparison of findings across studies difficult and has limited advances in aging research. The domain in which consensus on markers of successful aging is furthest developed is the domain of physical functioning. For example, walking speed appears to be an excellent surrogate marker of overall health and predicts the maintenance of physical independence, a cornerstone of successful aging. The purpose of the present article is to provide an overview and discussion of specific health conditions, behavioral factors, and biological mechanisms that mark declining mobility and physical function and promising interventions to counter these effects. With life expectancy continuing to increase in the United States and developed countries throughout the world, there is an increasing public health focus on the maintenance of physical independence among all older adults.

This study tested the effects of aging and race on responses to noxious stimuli using a wide range of stimulus modalities. The participants were 53 non-Hispanic Blacks and 138 non-Hispanic White adults, ages 45 to 76. The participants completed a single 3-hour sensory testing session where responses to thermal, mechanical, and cold stimuli were assessed. The results suggest that there are selected age differences, with the older group less sensitive to warm and painful heat stimuli than middle-aged participants, particularly at the knee. This site effect supports the hypothesis that the greatest decrement in pain sensitivity associated with aging occurs in the lower extremities. In addition, there were several instances where age and race effects were compounded, resulting in greater race differences in pain sensitivity among the older participants. Overall, the data suggest that previously reported race differences in pain sensitivity emerged in our older samples, and this study contributes new findings in that these differences may increase with age in non-Hispanic Blacks for temporal summation and both heat and cold immersion tolerance. We have added to the aging and pain literature by reporting several small to moderate differences in responses to heat stimuli between middle and older age adults.

Objective Pain in knee osteoarthritis (OA) has historically been attributed to peripheral pathophysiology; however, the poor correspondence between objective measures of disease severity and clinical symptoms suggests that non-local factors, such as altered central processing of painful stimuli, also contribute to clinical pain in knee OA. Consistent with this notion, recent evidence demonstrates that patients with knee OA exhibit increased sensitivity to painful stimuli at body sites unaffected by clinical pain. Design In order to further investigate the contribution of altered pain processing to knee OA pain, the current study tested the hypothesis that symptomatic knee OA is associated with enhanced sensitivity to experimental pain stimuli at the knee and at remote body sites unaffected by clinical pain. We further anticipated that pain sensitivity would differ as a function of the OA symptom severity. Older adults with and without symptomatic knee OA completed a series of experimental pain assessments. A median split of the Western Ontario and McMaster Universities Index of Osteoarthritis (WOMAC) was used to stratify participants into low vs. high OA symptom severity. Results Compared to controls and the low symptom group, individuals in the high symptom group were more sensitive to suprathreshold heat stimuli, blunt pressure, punctuate mechanical, and cold stimuli. Individuals in the low symptomatic OA group subgroup exhibited experimental pain responses similar to the pain-free group on most measures. No group differences in endogenous pain inhibition emerged. Conclusions These findings suggest that altered central processing of pain is particularly characteristic of individuals with moderate to severe symptomatic knee OA.

Objective To identify psychological profiles in persons with knee osteoarthritis (OA) and to determine the relationship between these profiles and specific pain and sensory characteristics, including temporal summation and conditioned pain modulation. Methods Individuals with knee OA (n = 194) completed psychological, health, and sensory assessments. Hierarchical cluster analysis was used to derive psychological profiles that were compared across several clinical pain/disability and experimental pain responses. Results Cluster 1 had high optimism with low negative affect, pain vigilance, anger, and depression, along with the lowest self-reported pain/disability and the lowest sensitivity to mechanical, pressure, and thermal pain (P < 0.01 for all). Cluster 2 had low positive affect with high somatic reactivity, while cluster 3 showed high pain vigilance with low optimism. Clusters 2 and 3 had intermediate levels of self-reported pain/disability and cluster 3 experienced central sensitization to mechanical stimuli. Participants in cluster 3 also displayed significant pain facilitation (P < 0.05). Cluster 4 exhibited the highest pain vigilance, reactivity, negative affect, anger, and depression. These individuals experienced the highest self-reported pain/disability, including widespread pain (P < 0.001 for all). Cluster 4 was most sensitive to mechanical, pressure, and thermal stimuli, and showed significant central sensitization to mechanical and thermal stimuli (P < 0.001 for all). Conclusion Our findings demonstrate the existence of homogeneous psychological profiles displaying unique sets of clinical and somatosensory characteristics. Multidisciplinary treatment approaches consistent with the biopsychosocial model of pain should provide significant advantages if targeted to profiles such as those in our OA sample.

Objective Knee osteoarthritis (OA) contributes significantly to disability in older individuals and racial/ethnic minorities are disproportionately affected. The present study aimed to characterize differences in clinical and experimental pain including pain inhibition among older African-Americans (AAs) and non-Hispanic whites (NHWs) with knee OA. Methods AAs and NHWs with knee OA (n=267) completed clinical and functional pain assessments including quantitative sensory testing (QST). We hypothesized that 1) AAs would display lower pain tolerance and higher heat, mechanical and cold pain ratings compared to NHWs; 2) AAs would display greater temporal summation compared to NHWs; 3) AAs would display reduced pain inhibition compared to NHWs; 4) AAs would demonstrate greater clinical pain and poorer function relative to NHWs; and 5) QST would significantly predict clinical pain within each race/ethnicity. Results AAs displayed increased pain sensitivity, temporal summation and reduced pain inhibition than NHWs. AAs reported greater clinical pain and poorer function than NHWs. Race/ethnic differences in clinical pain became non-significant when controlling for education and income, whereas differences in QST remained highly significant. Although pain inhibition predicted clinical pain in both groups, different QST measures were additionally predictive of clinical pain within groups. Conclusion Our study establishes race/ethnic differences in experimental and clinical pain and function in older individuals with knee OA. Our findings that different QST measures were associated with clinical pain within race/ethnic groups while reduced pain inhibition was important in all participants warrants further study evaluating common and group-specific pathophysiological mechanisms contributing to clinical pain in OA.

This study determined the stability of self-reported clinical pain characteristics and pain-induced interference with sleep and daily activities in people with spinal cord injury. The study followed up a previous survey that identified clinical pain patterns (i.e., neuropathic pain below the level of injury; upper-limb pain in tetraplegia; and severe, persistent pain). A confirmatory factor analysis (CFA) of the present study's data confirmed the previously observed pain patterns. The CFA also confirmed positive correlations between the surveys on individual pain characteristics (i.e., number of pain locations [r = 0.63, p < 0.001], number of descriptors [r = 0.61, p < 0.001], pain intensity [r = 0.68, p < 0.001], and temporal aspects [r = 0.47, p < 0.001]). Despite an overall stable clinical picture of pain, "aching" pain (p < 0.001) and sleep interference caused by pain (p < 0.001) significantly increased over time.