Inflammation Impact on Pain in Patients With Knee Osteoarthritis

Osteoarthritis (OA) of the knee and hip is the most common musculoskeletal joint disease worldwide. Although a major symptom of OA is chronic joint pain, which has a significant effect on patients' quality of life, the pain mechanisms remain largely unknown.

Recently, clinical studies have suggested the existence of a neuropathic component in OA pain [5]. Accumulating evidence has been indicating that painful OA patients show peripheral and central sensitization [3,16]. Quantitative sensory testing (QST) is a relevant way to assess peripheral and central sensitization in joint pain [9]. The majority of studies have administered mechanical stimuli, and the most commonly used modality have been pressure. A recent review concluded that that people with OA have lower Pressure Pain Thresholds (PPT), facilitated temporal summation and impaired conditioned (CPM) compared with healthy controls [5]. Also, recent evidence have link QST profiles to the development of chronic pain [29,38], which emphasises the importance of studying the central nervous system.

Inflammation markers have been correlated with the pain intensity [35], and systemic inflammation can leads to sensitization of peripheral nociceptors [1]. Recently it was reported that higher preoperative levels of TNF-α, MMP-13 and IL-6 in synovial fluid may indicate a smaller improvement in pain 2 years after TKR [15].

Injectable solutions of gold-thio-compounds have been used to treat rheumatoid arthritis for nearly 100 years [13,21]. Several studies suggest that gold ions reduces pain, joint swelling, inflammation, and increase joint motility [24,31,33]. Gold salt therapy (auranofin; RidauraR) has been vetted by the FDA and approved (May 1985) and recommended by the American College of Rheumatology as a Disease Modifying Anti Rheumatic Drug - DMARD (https://www.rheumatology.org).

Gold salts, whether injected or given orally, have been shown to be effective [33,37] in reducing joint pain. Studies report patients going to total remission [28] and others report a 30% reduction in symptoms [20,27]. In addition, Clark et al., 1997 [8] concluded in a Cochrane meta-analysis that systemic treatment with gold was highly effective compared to placebo.