Page 96 - JSOM Fall 2018

An Ongoing Series

Osteoarthritis

Pathophysiology, Prevalence, Risk Factors, and
Exercise for Reducing Pain and Disability

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Joseph J. Knapik, ScD ; Rodney Pope, PhD ; Robin Orr, PhD ; Ben Schram, PhD 4
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ABSTRACT
Osteoarthritis (OA) is a disorder involving deterioration of individuals with higher socioeconomic status; and those with
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articular cartilage and underlying bone and is associated with high school diplomas or higher levels of education. Globally,
symptoms of pain and disability. The incidence of OA in the hip and knee OA was ranked as 11th highest contributor to
military increased over the period 2000 to 2012 and was the disability among 291 medical conditions. Certain therapeutic
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first or second leading cause of medical separations in this pe­ modalities can relieve pain and improve physical functioning,
riod. Risk factors for OA include older age, black race, genet­ but these cannot alter the course of this degenerative disease. 5
ics, higher body mass index, prior knee injury, and excessive
joint loading. Animal studies indicate that moderate exercise The incidence of OA appears to be higher in the military than
can assist in maintaining normal cartilage, and individuals in comparable age­adjusted civilians, with differences between
performing moderate levels of exercise show little evidence these two groups becoming larger with increasing age. OA
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of OA. There is considerable evidence that among individuals was ranked the most common reason for medically related
who develop OA, moderate and regular exercise can reduce separation from service in early 2001 and the second most
pain and disability. There is no firm evidence that any partic­ common reason (after back pain) in early 2009 (after the
ular mode of exercise (e.g., aerobic training, resistance exer­ Iraq­Afghanistan conflicts were well underway). As in the ci­
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cise) is more effective than another for reducing OA­related vilian sector, there is evidence that OA incidence is increasing
pain and disability, but limited research suggests that exercise in the military over time. 6,8,9
should be lifelong and conducted at least three times per week
for optimal effects. In this article, we review the pathophysiology of OA, describe
the prevalence, incidence, and trends in the military, and ex­
Keywords: osteoarthritis; exercise; pain; disability amine the evidence that exercise can reduce the pain and dis­
ability associated with OA. This is the first of a series that will
address various interventions to reduce the pain and disability
associated with OA.
Introduction
Osteoarthritis (OA) is an orthopedic disorder characterized Pathophysiology
by progressive deterioration of articular cartilage and under­
lying bone and associated with symptoms of joint pain and OA is a degenerative joint disease involving progressive loss
disability. It most often affects the knees, hips, spine, and of articular cartilage, hardening and compacting of underly­
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joints of the hands. The overall age­adjusted prevalence of ing bone (sclerosis), and often formation of bony outgrowths
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OA in the United States in the years 1999 to 2014 was 9.7%; (osteophytes). Articular cartilage is a specialized type of con­
however, it more than doubled in this period from 6.6% to nective tissue that lines the bones where they connect within
14.3%. The increase was seen in many demographic groups: a joint. This cartilage normally provides a smooth, lubricated
men and women; white, black, and Hispanic populations; surface that allows for low­friction movement between bone
*Correspondence to joseph.knapik@JSOMonline.org
1 Dr Knapik served in the US military as a wheel vehicle mechanic, medic, Medical Service Corps officer, and Department of Defense civilian. He
is currently a senior epidemiologist/research physiologist with the Henry M. Jackson Foundation and an adjunct professor at Uniformed Services
University, Bethesda, Maryland, and Bond University, Robina, Australia. Dr Pope is professor of Physiotherapy at Charles Sturt University and
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coleads the Tactical Research Unit headquartered at Bond University. He has spent much of his 30­year career researching, practicing, and advis­
ing on injury risk management in military and other tactical populations. Dr Orr served in the Australian Regular Army for over 20 years as an
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infantry Soldier, physical training instructor, physiotherapist, and human performance officer. He currently serves in the Army Reserves and is an
associate professor and leader of the Tactical Research Unit at Bond University. Dr Schram serves as an officer in the Australian Army Reserve.
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He is involved in injury minimization, strength and conditioning, and validating fitness standards. He is an assistant professor at Bond University
and is the research and data coordinator for the Tactical Research Unit.
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