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 management. This page provides an 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 point:

• 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

Epidemiology

According to the 2021 Global Burden of Disease Study, in 2020, 595 million people had osteoarthritis (i.e. 7.6% of the global population). This number has increased by 132.2% since 1990. These figures are expected to continue to increase. By 2050, cases of:

• knee osteoarthritis are projected to increase by 74.9%
• hip osteoarthritis are projected to increase by 78·6%
• hand osteoarthritis are projected to increase by 48·6%
• other types of osteoarthritis are projected to increase by 95·1%

Increased prevalence has been linked to our ageing populations and an increase in obesity and joint injuries.

Risk Factors

Known risk factors for osteoarthritis include ageing, obesity, acute trauma, chronic overload, gender and hormone profile, metabolic syndrome, genetic predisposition and the gut-joint axis. 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 postures, 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)

Anatomic factors (joint deformities): the shape of a joint can impact the developement of osteoarthritis and certain variations in the shape of bones / joints have been associated with osteoarthritis of the hip and knee.

Pathophysiology of Osteoarthritis

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."

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

However, the exact pathological mechanisms of osteoarthritis are still unknown. Changes within the whole joint structure are believed to be due to an interplay between various tissues in the osteochondral complex (e.g. adipose tissue, synovial tissue, ligaments, tendons, muscles), and there is increasing evidence that low-grade, chronic inflammation plays a part in osteoarthrits.

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

Please watch the following optional video if you want to learn more about the pathology of osteoarthritis:

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
• bony tenderness

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

  However, x-rays can "underestimate the joint tissue involvement in OA, since they only visualize a component of the condition including cartilage loss that result in joint space narrowing and bony changes that result in subchondral sclerosis, cysts, and osteophyte formation. Once these changes are apparent on radiographs, the condition has significantly advanced."

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. 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."

There are different clinical classification criteria used to help identify individuals with osteoarthritis, including the European League Against Rheumatism (EULAR), the American College of Rheumatology (ACR), and the National Institute for Health and Care Excellence (NICE) clinical classification criteria. For more information on these criteria, please see Comparison of three sets of clinical classification criteria for knee osteoarthritis: a cross-sectional study of 13,459 patients treated in primary care.

The following criteria are based on the NICE guidelines:

• aged ≥ 45 years
• has movement-related joint pain
• has no knee morning stiffness or has knee morning stiffness that lasts ≤ 30 minutes

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. While there is no validated diagnostic criteria for early hip osteoarthritis, the American College of Rheumatology clinical classification criteria for hip osteoarthritis are as follows:

• hip pain in combination with:
  • <15° of hip internal rotation
  • erythrocyte sedimentation rate (ESR) of ≤45 mm/hour or ≤115° of hip flexion (a hip flexion measurement is used if ESR is not obtained)

Or

• hip pain and:
  • aged >50 years
  • ≥15° of hip internal rotation
  • pain with internal rotation
  • ≤60 minutes of morning stiffness

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

• 

  Figure 1. From left to right: knee with normal alignment, genu varus and genu valgus.

• 

  Figure 2. Heberden's and Bouchard's nodes.

Osteoarthritis Management

General management goals include:

• maintaining / gaining range of motion
• increasing muscular support
• decreasing joint stress
• managing pain

Medical management may include:

• medication, including anti-inflammatories, acetaminophen (paracetamol)
• encouraging weight loss
• surgical intervention (arthroscopy vs total joint replacements, etc)

Physiotherapy Management

"The clinical effect of PT [physical therapy] on pain and disability in hip or knee OA is substantial, while its associated costs are low."

Key physiotherapy interventions for the hip and knee include patient education and exercise rehabilitation.

Patient education topics might include:

• information about osteoarthritis and its potential consequences
• benefits of exercise / healthy lifestyle / weight loss (if in your scope of practice)
• treatment options
• if arthroplasty (joint replacement) is planned, education should provide information about the surgery, rehabilitation timeframes, assistive devices, benefits of prehabilitation (i.e. maintaining strength and fitness pre-operatively), post-operative considerations, lifestyle restrictions and any precautions that may be necessary

Exercise rehabilitation should focus on joint-specific and general exercises that are individualised for each person's goals, requirements and preferences.

The following table summarises an example of Frequency, Intensity, Time, and Type (FITT) principles for hip and knee osteoarthritis. It is adapted from Van Doormaal et al. A clinical practice guideline for physical therapy in patients with hip or knee osteoarthritis.

Table 1. Frequency, Intensity, Time and Type (FITT) Principles for hip and knee osteoarthritis.

FITT principle	Exercise recommendations
Frequency	Aim for at least 2 days per week of strengthening and 5 days of aerobic exercise
Intensity	Muscle strength training: Aim for 60-80% of one repetition maximum (1RM) or 50-60% 1RM for individuals who aren't used to strength training 2-4 sets 8-15 repetitions 30-60 seconds rest between sets Aerobic training: aim for more than 60% maximum heart rate (HRMax) or 40-60% for individuals who aren't used to aerobic exercise slowly build up intensity
Type	Aim for a combination of strength, aerobic and functional training Strength exercises: target large muscles around the knee and hip joints (e.g. knee extensors, hip abductors, knee flexors) repeat on both sides include functional exercises Aerobic exercise: low joint load exercises (e.g. walking, cycling, swimming, rowing, cross-trainer) Functional training: focus on activities that a patient typically finds difficult in daily life (e.g. walking, stairs, transitioning from sit to stand) Can also include balance, coordination, neuromuscular and range of motion exercises if indicated
Time	8-12 weeks of treatment, with one or more follow-up sessions (e.g. at 3 and 6 months post-treatment) Encourage ongoing self-management and continued exercise

Key considerations for exercise rehabilitation:

• include a warm-up / cool down
• increase the intensity of training gradually (e.g. once per week) to the maximum level for the patient
• reduce the intensity of the next session if joint pain increases after a workout and persists for more than 2 hours after
• for patients who are untrained or limited by pain / mobility, start with short sessions (10 minutes or less)
• offer alternatives to exercises
• vary the number of sets, repetitions, intensity, duration of each session, type of exercise, rests, etc in consultation with the patient

Other interventions to consider:

• mobilisations
• assistive devices