General Overview of Osteoarthritis for Rehabilitation Professionals

Original Editor - Shala Cunningham Top Contributors - Jess Bell

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. Conservative management 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 now 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, 595 million people had osteoarthritis in 2020 (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%, cases of hip osteoarthritis are projected to increase by 78.6%, cases of hand osteoarthritis are projected to increase by 48.6% and cases of other types of osteoarthritis are projected to increase by 95.1%.

Increased prevalence has been linked to 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) with females more likely to develop osteoarthritis.

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

Pathology 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 osteoarthritis.

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”, such as walking, sports, dancing, etc.
• bony tenderness

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 clinical criteria for knee osteoarthritis 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

Specific clinical criteria for identifying spine osteoarthritis (e.g. pain, morning stiffness, painful / reduced range of motion) are not yet available, but there is a known link between these criteria and lumbar disc degeneration.

Hand Osteoarthritis

The American College of Rheumatology criteria for osteoarthritis of the hand is as follows:

• hand pain, aching or stiffness on most days of the previous month, and three of the following four criteria:
  • hard tissue enlargement of ≥ of 10 selected hand joints
  • metacarpophalangeal joint swelling in ≤ joints
  • enlargement of the hard tissue of ≥2 of the distal interphalangeal joints
  • deformity of ≥1 of 10 selected hand joints

Outcome Measures

There are a range of outcome measures for osteoarthritis. Please see here for more information.

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

"Clinical guidelines for management of knee OA emphasise non-drug non-surgical strategies that focus on self-help and patient-driven options rather than clinician-delivered passive therapies."

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
• weight management
• intra-articular corticosteroid injections
• surgical intervention (i.e. total joint replacement)
  • please note that the American Academy of Orthopaedic Surgeons (AAOS) has "published moderate recommendations against using joint lavage and debridement as a treatment for symptomatic OA"

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

Patient education topics might include:

• information about osteoarthritis
• benefits of exercise and strengthening / healthy lifestyle / weight management (these conversations may vary depending on your scope of practice and may require referral to another health professional)
• treatment options, as well as benefits and risks to ensure informed consent
• if arthroplasty (joint replacement) is planned, physiotherapists might provide information on 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

Exercise rehabilitation should focus on joint-specific and general exercise / physical activity. Exercise programmes should be individualised for each person's goals, requirements and preferences. The following sections provide some general advice based on recent research for hip and knee osteoarthritis.

Knee osteoarthritis: A Cochrane review from 2015 looked at any land-based therapeutic exercise programmes for individuals with knee osteoarthritis, regardless of content, duration, frequency or intensity of the exercise programme, and found that: "any type of exercise programme that is performed regularly and is closely monitored can improve pain, physical function and quality of life related to knee OA in the short term."

Hip osteoarthritis: A 2014 Cochrane review also found that any "land‐based therapeutic exercise programmes can reduce pain and improve physical function among people with symptomatic hip OA." The programmes from the included studies were either performed independently or supervised.

The following table provides a summary of Frequency, Intensity, Time, and Type (FITT) principles for hip and knee osteoarthritis, based on recent research. Most of the information 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 please note that for knee osteoarthritis, Husted et al. found that 2 sessions of strength training per week produce the same strength improvements as four or six sessions, but two sessions are better for pain and function (this may be due to the increased recovery time associated with two sessions compared to four or six)
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 the PEAK (Physiotherapy Exercise and Physical Activity for Knee Osteoarthritis) study recommends that participants work hard or very hard Van Doormaal et al. recommend: 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 it is possible to use an activity tracker to establish a patient's baseline and build up from here
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) the strengthening exercises used in the PEAK study for knee osteoarthritis are listed here repeat on both sides include functional exercises the PEAK study for knee osteoarthritis recommends starting with three exercises (one quadriceps, one hip / gluteal, one hamstrings / gluteal), and increasing this to a maximum of six exercises in week two (two quadriceps, one hip / gluteal, one hamstrings / gluteal, one calf, one optional extra) 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, transferring 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

The following videos include some ideas for exercises. The video on the left focuses on knee osteoarthritis and the video on the right demonstrates hip exercises. The strengthening exercises used in the PEAK study for knee osteoarthritis are listed here.

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

Other Rehabilitation Interventions

Other interventions might include:

• manual therapy (should only be considered alongside therapeutic exercise)
• assistive mobility devices (e.g. walking sticks) for individuals with lower limb osteoarthritis
• the NICE guidelines recommend against the routine use of insoles, braces, tape, splints or supports, unless:
  • there is evidence of joint instability or abnormal biomechanical loading AND
  • therapeutic exercise will not be effective or is not suitable without an aid or device being used AND
  • the aid or device will likely improve function / movement

Please note that the NICE guidelines do not recommend the following treatments for individuals with osteoarthritis due to a lack of benefits:

• acupuncture
• transcutaneous electrical nerve stimulation (TENS)
• ultrasound
• interferential therapy
• laser therapy
• pulsed short-wave therapy
• neuromuscular electrical stimulation (NMES)