Osteoarthritis (OA) is the most common form of arthritis worldwide, with a higher incidence in high-income countries and older individuals. In the United States alone, over 32.5 million individuals have been diagnosed with OA, 3 million of which are Hispanic, an ethnic minority [1–4]. Knee OA (KOA) is the leading cause of lower extremity disability, and as of 2010, was ranked the 11th highest contributor to global disability [5]. Studies including diverse populations are needed to more fully understand the total burden of OA in order to better address unmet needs of both the patient and the medical community serving them.
The diagnosis of OA is usually based on clinical assessment and confirmed by routine plain radiographs[6]. Patients typically report activity-related joint pain that is associated with morning stiffness of less than 30 minutes duration [6, 7]. However, this presentation is not consistent across all patient populations. Like other chronic diseases, the presentation and subsequent morbidity of KOA demonstrates considerable variability across different races and, more recently, ethnicities [8–12]. For example, the Johnston County OA project demonstrated statistically significant differences in both pain severity and radiographic severity (Kellgren and Lawrence [K-L]) scores between African Americans and Caucasians with symptomatic KOA at initial presentation [13, 14]. Other investigators have corroborated this finding by reporting greater pain severity among African Americans compared to non-Hispanic White persons (NHWP) with hip and knee OA [15–21]. Both studies utilized race, an observable characteristic with social implications, as the independent variable between groups. Recently, Hoffman et al. denoted that there are no biological differences in pain experience based on race alone yet there are racial biases in the treatment and assessment of pain [22].
Ethnicity, on the other hand, may or may not carry a different race; however, the term attempts to capture the culture of people in a given geographic region, including their language, heritage, religion and customs [15]. Hollingshead et al. discussed how ethnicity is involved in the processing and reporting of pain [23, 24]. Moreover, a recent study observed that Hispanic persons (HP) report greater pain sensitivity and less pain tolerance than NHWP [23]. Furthermore, a study by Wang studied four different ethnicities (East Asian, African American, Hispanic and Caucasian) and found differences in pain sensitivity between ethnicity after capsaicin administration [25, 26]. Finally, Levy et al. highlighted differences in symptom severity on presentation for a well-known chronic illness, alcoholic liver disease, between Caucasian and Hispanics [27].
Although current data is limited, in addition to studies indicating an association between pain experience, disease severity, and ethnicity, there are findings specific in Hispanics with chronic pain regarding pain intensity and coping mechanisms. Studies utilizing population-based data from the third National Health and Nutrition Examination Survey (NHANES-III) demonstrated that HP with self- reported arthritis are twice as likely to self-report symptoms of activity limitation when compared to NHWP [2]. HPs with an assigned diagnosis of arthritis also tend to report greater pain scores as measured by the Visual Analog Scale (VAS) [15]. Furthermore, when compared to NHWP, HPs have a greater propensity to utilize pain-catastrophizing coping mechanisms to address any physical manifestation of chronic pain [15, 24]. Previous studies have highlighted the psychosocial aspect of arthritic pain and how implications in socioeconomic, psychological, and environmental factors have a substantial influence on an individual’s perception of their self-efficacy and quality of life [26–28].
One maladaptive strategy utilized more commonly in Hispanics for coping with chronic pain is pain catastrophizing. This is a tendency to develop a belief that the pain will not resolve (Helplessness), a constant repetitive dwelling on the negative aspects of the pain (Rumination) and exaggerating/ falsely intensifying the perceived pain stimulus (magnification). Greater pain catastrophizing is associated with greater pain and functional limitation. Additionally, greater pain catastrophizing has been independently associated with lower socio-economic status [9, 29–32]. Green et al. expanded on this claim and underlined that neighborhood socioeconomic status mediated chronic pain experience in younger White and Black individuals [33]. They argued neighborhood socioeconomic status (NSES) mediated the pain experience differences identified between races. Therefore, to explore if differences in pain experiences existed between ethnicity, NSES or a surrogate measure may be noteworthy [31, 33].
The role of socioeconomic factors and variation in values, attitudes, and beliefs regarding medical treatments are not well understood. To our knowledge, there are limited data investigating HP with KOA. One recent study has shown that HP reported higher pain and symptom scores despite fewer changes on plain radiographs compared with NHWP with KOA [34]. The purpose of the present study was to determine if there are differences in pain catastrophizing, functional limitation, and pain severity between HP and NHWP with KOA after adjusting for socioeconomic status (SES) and radiographic disease severity. Investigating a convenience sample of patients from southern Florida, a region somewhat unique with its high prevalence of HP, our hypothesis is that there are differences in reporting of pain catastrophizing, pain severity, and functional limitations between the two ethnicities that will persist after controlling for covariates including SES and KL grade.