۱- Introduction

۲- Methods

۳- Results

۴- Discussion

References

Abstract

Background
A source of myofascial pain and myofascial trigger points (MTrPs) in muscles of the knee area could play a crucial role in the management of pain in osteoarthritis patients. The aim of this study was to describe and compare demographic, clinical and myofascial pain syndrome characteristics in older adults with knee osteoarthritis by sex and age distribution.
Methods
A cross-sectional study was carried out. 114 patients with osteoarthritis were recruited in older-adult care centers. The diagnosis of active and/or latent MTrPs (AMTrPs/LMTrPs) was performed. Numerical Pain Rating Scale, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Barthel Index, Timed Up and Go Test (TUG), Mini-Mental State Examination, EuroQol Group 5-Dimension Self-Report Questionnaire, chronicity, number of falls, and medication use were collected. All data were compared by sex (male or female) and age (< ۷۰, ۷۰–۸۰, or > ۸۰ years) distributions.
Results
The most prevalent muscles with AMTrPs and LMTrPs were the quadriceps vastus medialis (75.43%) and lateralis (65.78%), respectively. The clinical characteristics showed significant differences (P<0.05) for chronicity, WOMAC functionality and total scores, TUG, falls rate and medication between males and females, as well as for chronicity, Barthel index and TUG between age distributions. There were not any significant differences (P>0.05) by sex or age distribution according to the number and presence of active and latent MTrPs.
Conclusions
The demographic and clinical features of older adults with knee osteoarthritis may be influenced by sex and age distribution. Nevertheless, the myofascial pain syndrome associated with knee osteoarthritis did not seem to be related to sex or age distribution.

Introduction

Osteoarthritis (OA) is one of the main reasons for disability within the elderly population; it has a high prevalence in society in general [1,2]. The knee is the most frequently affected joint among those associated with OA, and often results in disability [3,4]. OA of the knee is a syndrome distinguished by the presence of pain, and often corresponds with radiological and laboratory findings [5]. However, the real pathogenesis is still poorly understood. Many studies have shown a disparity between the pain description and the results from x-ray imaging [6–۸]. OA has an estimated prevalence of seven million population within the United States [9]. More than in any other joint, OA of the knee causes a large number of the clinical symptoms that lead to impairment [10–۱۲]. The estimated prevalence of OA in Spain is 46% for women and 21% for men over the age of 45 years of age [13]; OA of the knee represents 10% of this [14]. In this same country, knee OA had an economic impact of 4700 million euros only in 2014, an amount comparable to 0.5% of the Gross Domestic Product in that same year. In conclusion, we can state that this. This syndrome has become a major health issue in every country [15]. Although the etiology of knee OA remains undefined, it is known that its incidence increases with age [16,17]. In addition, being overweight becomes a risk factor for the development and progression of this syndrome and it can even be related to joint replacement [18–۲۰]. One of the latest critical reviews found that a source of myofascial pain in knee OA and the existence of myofascial trigger points (MTrPs) in muscles of the knee area could play a crucial role in pain and impairment in patients with OA [21]. In fact, considering that MTrPs are known to be tender spots within a taut band of voluntary muscles that can produce signs and symptoms related to the sensitive, motor or autonomic component, their prevalence may reach 100% in patients with OA knee, specifically in the internal gastrocnemius [92%] and vastus medialis muscles [67%] [22]. Although these muscles have active myofascial trigger points (AMTrPs) that produce spontaneous and recognized pain, latent myofascial trigger points (LMTrPs) may play a role in limiting range of motion, altering muscle contraction patterns, and generating local or referred pain when manual pressure is applied [23,24].