General Overview of Osteoarthritis for Rehabilitation Professionals

Original Editor - Shala Cunningham Top Contributors - Jess Bell

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Introduction

Osteoarthritis (OA) is a common chronic health condition. It can cause pain, decreased function, poor sleep, decreased mental health and reduced quality of life. It is also associated with an increased risk of cardiovascular disease, diabetes, hypertension and mortality. General rehabilitation strategies for osteoarthritis include education, exercise and weight loss. This page provides a general overview of osteoarthritis, including epidemiology, risk factors and pathology, before considering diagnosis and management trends.

Definition

The Osteoarthritis Research Society International (OARSI) defines osteoarthritis as: “a disorder involving movable joints characterized by cell stress and extracellular matrix degradation initiated by micro- and macro-injury that activates maladaptive repair responses including pro-inflammatory pathways of innate immunity. The disease manifests first as a molecular derangement (abnormal joint tissue metabolism) followed by anatomic, and/or physiologic derangements (characterized by cartilage degradation, bone remodeling, osteophyte formation, joint inflammation and loss of normal joint function), that can culminate in illness.”

Key points:

• osteoarthritis has traditionally been described as a degenerative cartilage disease, but our understanding has evolved and we know that there is a breakdown of the cartilage, as well as structural changes across the whole joint
• subchondral bone lesions precede cartilage degeneration

Epidemiology

It is estimated that 240 million individuals have symptomatic osteoarthritis, with a current prevalence rate of around 15%. This figure is expected to increase to 35% by 2030. This would make osteoarthritis the “single greatest cause of disability globally”. Increased prevalence has been linked to our ageing populations and an increase in obesity and joint injuries.

Risk Factors

"Most cases of OA have a clear predisposing condition, such as genetics, trauma, aging, or obesity, leading to the idea that OA describes a common endpoint with different etiologies."

Known risk factors for osteoarthritis, include ageing, obesity, acute trauma, chronic overload, gender and hormone profile, metabolic syndrome and genetic predisposition. However, osteoarthritis is not "the inevitable consequence of these factors [...and…] different risk factors may act together in the pathogenesis of osteoarthritis".

Ageing is characterised by progressive tissue loss and decreased organ function, and it "represents the single greatest risk factor for OA"

Obesity is considered "the most prevalent preventable risk factor for developing osteoarthritis":

• previously obesity was considered a primary risk factor in knee osteoarthritis because of its impact on biomechanics, but it is now understood that it increases risk by altering metabolism and inflammation
• obesity increases the risk of osteoarthritis in various joints, including the hand, hip, knee, ankle and spine
• obesity increases the risk of osteoarthritis in both males and females, but the effect size is greater in females

Acute trauma / joint injury are considered "potent' risk factors for osteoarthritis. 

Chronic overload:

• various occupational ergonomic risk factors for osteoarthritis have been proposed, including force exertion, demanding posture, repetitive movements, hand-arm vibration, kneeling / squatting, lifting and climbing
  • these risk factors can increase the risk of developing knee or hip osteoarthritis compared to no exposure
  • however, because the quality of evidence is currently low, there is "limited evidence of harmfulness"
• another systematic review found that physically demanding jobs (e.g. construction work, floor and bricklaying, fishing, farming, etc) are associated with increased risk of knee and hip osteoarthritis, and there may be a dose-response relationship

Gender and hormone profile: there are gender differences in osteoarthritis across all joints (the cervical spine is one potential exception)

Joint deformities: previous variation in the shape of bones / joints has been associated with osteoarthritis of the hip and knee.

Pathology

Osteoarthritis is a "dynamic and complex process, involving inflammatory, mechanical, and metabolic factors that result in the inability of the articular surface to serve its function of absorbing and distributing the mechanical load through the joint that ultimately leads to joint destruction."

Its exact pathological mechanisms are still unknown, but changes within the joint are due to an interplay between various tissues in the osteochondral complex (e.g. adipose tissue, synovial tissue, ligaments, tendons, muscles).

Osteoarthritis is typically characterised by:

• degradation / destruction of the articular cartilage
• surface irregularities
• osteophyte formation
• subchondral bone remodelling / thickening
• synovial inflammation
• secondary inflammation of periarticular structures

It is a "heterogeneous disease that impacts all component tissues of the articular joint organ."

Clinical Features

The pathological changes and symptoms caused by osteoarthritis vary considerably in each person. But typical signs and symptoms associated with osteoarthritis include:

• decreased range of motion
• stiffness
• pain
• deformity
• crepitus
• decreased mobility and functional limitations
• reduced / loss of ability to engage in “valued activities”, including walking, dancing, etc

These clinical changes / signs might only start to appear towards the end of disease progression.

Diagnosis

Osteoarthritis can be confirmed radiographically on x-ray. Radiographic findings include:

• joint space narrowing
• osteophytes
• subchondral sclerosis
• cyst formation
• abnormalities of bone contour
• ankylosis

Clinical vs Radiographic Osteoarthritis

Knee Osteoarthritis

Radiographic knee osteoarthritis requires structural changes on x-ray while clinical knee osteoarthritis is diagnosed based on a patient’s symptoms and the clinical examination. However, radiography "is disputed because structural findings appear relatively late in the course of the disease and symptoms are not always associated with the structural findings"

Key clinical signs:

• knee pain and at least three of the following:
  • aged over 50 years
  • more than 30 minutes of morning stiffness
  • crepitus
  • bony tenderness
  • bony enlargement
  • no palpable warmth

Hip Osteoarthritis

Hip osteoarthritis has traditionally been diagnosed based on radiographic features, like the Kellgren and Lawrence score, but many guidelines recommend against using radiography as a diagnostic tool. However, there is also no validated diagnostic criteria for early hip osteoarthritis, despite a general focus on early diagnosis

Key clinical signs:

• hip pain with:
  • less than or equal to 15 degrees of hip internal rotation
  • less than or equal to 115 degrees of hip flexion

Or

• hip pain with:
  • aged more than 50 years
  • less than or equal to 60 minutes of morning stiffness
  • pain on internal rotation
  • less than or equal to 15 degrees of hip internal rotation

Spine Osteoarthritis

There are no specific clinical criteria for identifying spine osteoarthritis (e.g. pain, morning stiffness, painful / reduced range of motion), but there is a known link between these criteria and lumbar disc degeneration.

Joint Deformities

Specific joint deformities to look out for:

• Heberden's nodes
• Bouchard's nodes
• genu varus/ valgus