Osteoarthritis Disease Background

Introduction

Osteoarthritis is a clinical syndrome of joint pain with different degrees of limitation in function and decreased quality of life. It is the most common form of arthritis and is the leading cause of disability of the lower extremity in older adults. It may not be secondary to aging and does not automatically progress. It most often occurs in the hands (ends of the fingers and thumb), spine (neck and lower back), knees, and hips.  

Epidemiology

There is approximately 3.8% worldwide incidence of knee osteoarthritis, increasing with age to >10% in individuals >60 years old. Glenohumeral osteoarthritis is more common in women and is most commonly seen in patients >60 years of age. Generally, it is more common among women than men. 

According to the Global Burden of Disease study in 2017, approximately 61.2 million Chinese are burdened by osteoarthritis with an age-standardized prevalence of 3.1%. Its prevalence was similarly higher among women at 3.8% as compared to 2.4% among men. Several studies have reported that the prevalence of knee osteoarthritis in the country varied from 4.6% to 39.1%. Among those aged ≥60 years old, knee osteoarthritis affects 42.8% of women and 21.5% of men. In a study employing the 2010–2013 Korea National Health and Nutrition Examination Survey, the prevalence of knee osteoarthritis among Korean adults was 35.1%.  

In 2019, the Global Burden of Disease estimated that around 62 million individuals are affected in India. 

In Indonesia, the prevalence remains high at 15.5% among men and 12.7% among women. In Malaysia, the prevalence of osteoarthritis was estimated to be around 1.1% to 5.6%. Consistently, according to the study by the Community Oriented Program for the Control of Rheumatic Diseases (COPCORD), approximately 9.3% experienced knee pain, more than half of which was consistent with osteoarthritis. In Singapore, approximately 17,000 disability-adjusted life years lost were reported. Approximately 8.4% is affected in Thailand.

Pathophysiology

It is the process of progressive softening or localizing loss of cartilage accompanied by the remodeling of adjacent bone and inadequate metabolic repair resulting in structural joint changes which cause pain and functional disability in patients with osteoarthritis. 

Risk Factors

Age  

More than 80% of individuals older than 75 years old are affected. It is not common in patients <40 years old unless with a history of trauma.  

Female Gender  

There is a higher risk for knee osteoarthritis after menopause for unclear reasons but it may be related to hormones, genetics, or other undetermined factors.  

Genetic Predisposition  

The influence of genetic factors varies in different subsets of osteoarthritis, ranging from 40-70%.  

Obesity  

Obesity increases the risk for symptomatic and progressive osteoarthritis. It increases the risk for knee osteoarthritis due to the increased mechanical stress on the joints and altered joint biomechanics secondary to changes in posture, gait, and level of physical activity. It increases stiffness in the subchondral bones and facilitates cartilage breakdown.  

Joint Trauma or Malalignment  

Joint trauma or malalignment results in the rapid development of osteoarthritis or starts the process causing symptomatic osteoarthritis later in life. Selected occupational usage and repetitive, high-impact sports are strongly related to joint injury, increasing the risk for lower extremity osteoarthritis. 

Classification

Osteoarthritis is classified as primary or secondary based on the cause or major predisposing factor; both have altered cartilage physiology.  

Primary osteoarthritis is the most common classification and with no known cause.  

Secondary osteoarthritis has an identifiable etiology but is pathologically similar to primary osteoarthritis. Common causes are metabolic diseases (eg hemochromatosis, acromegaly), anatomic causes (eg developmental hip dislocation), trauma (joint surgery, intra-articular fractures, ligament or meniscus damage, malunion), or complication of an inflammatory disorder (septic arthritis, ankylosing spondylitis, rheumatoid arthritis, and psoriatic arthritis).