Knee osteoarthritis (gonarthrosis)

What is knee osteoarthritis?

Knee osteoarthritis, also known as gonarthrosis, is a condition that can affect the entire joint: the cartilage, bone, ligaments, joint capsule, and muscles. ¹ It becomes more common with age, but it is not a normal or inevitable part of aging. ²

Articular cartilage covers the bone surfaces and helps with gliding and load distribution. ³ In osteoarthritis, its structure may change along with that of other joint tissues. ⁴

Osteoarthritis is not limited to the cartilage. All the structures that make up the knee joint can be affected. The bone beneath the cartilage, the ligaments, the capsule surrounding the joint, its thin lining that produces the lubricating fluid, and the surrounding muscles: all of these tissues can be involved in the changes associated with osteoarthritis.

Structures Affected by Knee Osteoarthritis

Osteoarthritis can affect the cartilage, the bone beneath the cartilage, the ligaments, the joint capsule, and the muscles ⁵. The nature and extent of these changes depend on the individual and the stage of the disease ⁶.

Osteoarthritis is a joint disease whose progression and symptoms vary widely. ⁷ Osteoarthritis does not always progress at the same rate and can also affect other joints. In a study following 1,578 people with knee pain and radiographic findings of varying severity, 86% were in the group whose joint space remained stable over eight years ⁸. To learn more about the forms of osteoarthritis that affect the back, see our guide on lumbar osteoarthritis.

What Are the Symptoms of Knee Osteoarthritis?

Common symptoms of knee osteoarthritis include progressive pain, morning stiffness, and a crunching sensation in the knee. ⁹ However, knee osteoarthritis does not always cause symptoms. Many people live with osteoarthritis without experiencing any symptoms: among people with osteoarthritis visible on X-rays, the proportion reporting pain ranges from 15% to 81%, depending on the study ¹⁰. Discomfort can vary from day to day.

This disconnect between osteoarthritis and pain often surprises people. You can have significant osteoarthritis visible on imaging and no pain at all. You can also have minimal osteoarthritis and many symptoms ¹⁰. This discrepancy is evident across the groups studied: it explains why an imaging result alone cannot predict how much pain a person will experience. To better understand this paradox, read our article “Is It Really Your Osteoarthritis That’s Causing Your Pain?”

Common Symptoms of Knee Osteoarthritis

Stiffness upon waking or after periods of inactivity may accompany osteoarthritis and subside with movement. Its duration varies and does not, on its own, confirm the diagnosis.

Over several years, pain may remain stable, decrease, or increase. A review focusing primarily on early-stage or moderate osteoarthritis reports that pain remained stable in about 85% of participants, decreased in 8%, and increased in 7% ¹¹. These proportions reflect pain trajectories and do not measure the effect of physical therapy treatment. They do not rule out day-to-day variations in pain.

If your symptoms are limiting your activities or causing you concern, an evaluation can help you better understand your situation. For knee pain, the consultation is designed to identify your needs and select appropriate treatments, with no standard waiting period.

What Are the Causes and Risk Factors?

Age, a previous knee injury, and a higher weight relative to height are associated with an increased risk of osteoarthritis ¹². In a U.S. survey, 12.1% of people aged 60 and older had both radiographic signs and symptoms in the knee ¹³. This figure reflects the U.S. population and is based on a definition that combines symptoms and X-ray findings. In a cohort study conducted in North Carolina, the estimated risk of symptomatic osteoarthritis by age 85 was 44.7% overall and 56.8% among individuals with a history of knee injury ¹⁴. This group included Black and White adults aged 45 and older living in rural areas. These population-based data do not predict an individual’s course of the disease.

Osteoarthritis does not develop overnight. For most people, it is a slow process that takes place over several years, and those who have it live with it for about 30 years on average ¹⁵. The rate of progression, however, varies greatly from person to person: at least one in seven people who develop knee osteoarthritis experience rapid progression to an advanced stage, sometimes in less than twelve months ¹⁶. A rapid or unusual worsening of symptoms warrants a reevaluation.

Risk Factors for Knee Osteoarthritis

You can make changes to certain habits that support knee health. Regular physical activity can reduce pain and improve function ¹⁷. For people who are overweight, losing 5% to 10% of their body weight can also improve pain, difficulties with daily activities, and quality of life ¹⁸.

However, the effects on the joint’s appearance remain uncertain. In the part of the knee located between the femur (the thigh bone) and the tibia (the shin bone), a review found no clear change in the severity visible on X-rays or in the shape of the cartilage after more than six months of exercise ¹⁹. The review on weight loss also found no consistent effect on changes visible on imaging ²⁰.

An injury such as a knee sprain or an anterior cruciate ligament (ACL) tear can increase the long-term risk of osteoarthritis: a history of knee injury is associated with a higher incidence of knee osteoarthritis. The meta-analysis calculates an odds ratio of 4.20. This measure compares the presence and absence of osteoarthritis between groups; it does not mean that the probability of osteoarthritis is four times higher ²¹. These observational studies establish the association but do not allow for quantifying an individual’s risk following a specific type of sprain.

How Is Knee Osteoarthritis Diagnosed?

The diagnosis of knee osteoarthritis is based primarily on the patient’s history of symptoms and a clinical examination: a comprehensive clinical evaluation may be sufficient to make a confident diagnosis ⁹. In the cited review, the proportion of people with radiographic osteoarthritis—that is, osteoarthritis visible on an X-ray—who reported pain ranged from 15% to 81%, depending on the study. An X-ray should therefore not be interpreted in isolation ¹⁰.

An X-ray showing osteoarthritis is not enough to explain your pain. The healthcare professional compares the image with your symptoms and the results of the physical exam.

Diagnostic Methods

A healthcare professional can diagnose knee osteoarthritis by asking you about your symptoms and examining your joint. An X-ray is usually not necessary to confirm the diagnosis or begin treatment ²². In fact, 11 of the 18 evidence-based recommendations advise a clinical diagnosis without confirmation by X-ray ²³. An X-ray may be ordered if the signs are atypical or suggest another condition, or if the clinical condition deteriorates unexpectedly.

When to Consult a Physiotherapist for Knee Osteoarthritis?

It’s a good idea to consider seeing a physical therapist when symptoms of knee osteoarthritis limit your activities.

Demandez un avis médical urgent si le genou est très douloureux, si vous ne pouvez pas le bouger ou prendre appui, ou s’il devient très gonflé ou déformé. Ces signes demandent des soins même sans blessure récente. Un genou qui se bloque, qui lâche ou qui produit un clic douloureux demande aussi un avis urgent. Un clic sans Pain est courant. Une forte fièvre ou une sensation de chaud, de froid ou de frissons, associée à une rougeur ou à une chaleur autour du genou, demande également une évaluation urgente. Ces signes sont décrits par le service public de santé britannique sur la Knee pain²⁴.

In Quebec, you have direct access to a physiotherapist without a medical prescription. This accessibility allows for a quick evaluation. To know what to expect, consult our article on what happens during a physiotherapy evaluation.

Signs That an Evaluation Would Be Helpful

Your physiotherapist will assess your situation and determine if physiotherapy can help you. If your condition requires further medical investigation, he or she will refer you to the appropriate professional.

Does physical therapy work for knee osteoarthritis?

Physical therapy, particularly through exercise, can reduce pain and improve function in people with knee osteoarthritis. Physical therapy is also one of the non-surgical options for hip osteoarthritis. A targeted plan primarily includes education, therapeutic exercises, and a progression tailored to the individual. Education about osteoarthritis and a structured exercise program—with or without weight management—are the recommended core treatments, and decisions are made based on each individual’s profile ²⁵. In clinical practice, therefore, the program is tailored to the individual rather than following a generic plan.

The BEEP trial compared three physical therapy programs: standard advice and exercises, more individualized exercises, and support for performing them regularly. All three groups experienced improvements in pain and function, with no demonstrated additional benefit from the more individualized program ²⁶.

Another analysis shows that people with more pain or greater functional limitations at the outset appear to benefit more from exercise ²⁷.

Data on exercise show an average reduction in pain and an improvement in function among people with knee osteoarthritis ¹⁷. The review includes 139 trials that randomly assigned participants to treatment groups. The certainty of the evidence is low to moderate. The average benefit remains modest, and its impact on daily life remains uncertain. An individual’s response may therefore differ from this average. ²⁸ Education and structured exercise are part of the standard of care and aim to reduce pain and improve function ²⁵.

La Manual therapy peut être envisagée en complément des exercices, alors que l'éducation et les exercices structurés demeurent les traitements de base²⁵. Un guide britannique publié en 2022²⁹ réserve cette possibilité aux personnes ayant de l’arthrose du genou ou de la hanche, en complément des exercices. Les données ne permettent pas de mettre la Manual therapy seule à ce niveau: une revue de onze revues systématiques trouve des conclusions incohérentes, neuf de ces revues étant de qualité méthodologique très faible et deux de faible qualité³⁰. Certaines observent quand même un bénéfice à court terme, alors la réserve porte sur la qualité des données et sur la place du traitement, pas sur une absence d'effet. Le dosage des exercices doit être adapté aux besoins, aux capacités et à la progression de chaque personne.

The physical therapist works with you to choose exercises based on your goals, your health, and how easily you can incorporate them into your daily routine. People who experience more pain or have greater difficulty moving at the outset seem to benefit more from the exercises, especially in the short term. The average benefits remain small to moderate in the medium and long term ²⁷. A comprehensive evaluation assesses, among other things, the strength of the quadriceps (the muscle at the front of the thigh), any limited activities, and your preferences in order to tailor the treatment. Follow-up visits allow for a review of your goals and adjustments to the exercises if the expected improvement does not occur.

The exercise programs studied lasted from two to 104 weeks. This duration refers to the research programs, not a mandatory timeframe before improvement occurs ¹⁷. Physical therapy does not cure osteoarthritis or reverse joint changes, but the exercises do, on average, reduce pain and improve function. Changes in your pain, gait, and activities are used to adjust the program over the course of your appointments.

What Are the Physiotherapy Treatments for Knee Osteoarthritis?

Physical therapy for knee osteoarthritis includes information, strengthening exercises, and activities tailored to your abilities. ³¹ The evaluation helps identify the factors that may influence your symptoms and tailor the exercises, activities, and, if necessary, other interventions.

Elements Evaluated in Physiotherapy

Physiotherapy Interventions

The exercises are designed to reduce pain and improve your functional abilities. In the 2024 review, the analyses did not show that any one type of exercise produced better results than the others ¹⁷. For knee mobilization, the evidence is less clear: the quality of the reviews on manual therapy is generally low or very low ³⁰.

Changes in the joint may remain visible even as symptoms subside: a review of exercise programs lasting more than six months found no clear change in the severity visible on X-rays or in the shape of the cartilage between the femur and the tibia ¹⁹. The data remain limited, and estimates lack precision. Some findings suggest a beneficial effect on the composition of patellar cartilage—that is, the substances that make it up—but this possibility remains uncertain. The extent of visible changes does not perfectly correlate with pain or disability ¹⁰. Exercise and education can reduce pain and improve function, but the extent of the effect varies from person to person. Learn how physical therapy treatment works to know what to expect.

What can you do at home for knee osteoarthritis?

Walking and exercises tailored to your abilities can help you manage knee osteoarthritis at home. You may experience a temporary increase in pain at first ²⁸. Adjust the duration and intensity based on how your body responds and your physical therapist’s advice. Adverse effects reported in trials mainly include pain, but other events have also been noted. The 2024 review specifically mentions a fall during an exercise that resulted in a head injury classified as severe. Exercises should therefore be tailored to your abilities and your risk of falling ¹⁷.

Tips based on your current activity level

Practical tips for daily life

• Temporarily stop movements that are too painful, then gradually resume them.
• Adjust your position as needed for comfort and take active breaks when you're sitting for long periods of time
• Be active every day according to your tolerance and gradually increase your activity level

About Weight Loss

For some people who are overweight and want to address this issue, dietary weight management can be part of their treatment ²⁵. In adults with obesity and mild to moderate knee osteoarthritis, a 5% to 10% weight loss improved pain, difficulties reported in daily activities, and the physical component of quality of life ¹⁸. The goal and approach should be tailored to the individual’s preferences, overall health, and risk of frailty, ideally in consultation with a dietitian.

Focus on regular physical activity, a balanced diet, and good sleep. For nutritional guidance, consult a nutritionist.

How can I reduce my chances of developing knee osteoarthritis?

Injury prevention and weight management help address two risk factors for knee osteoarthritis, though they do not guarantee that it can be prevented. Physical activity also supports overall health. The Canadian guidelines of at least 150 minutes of cardiovascular activity per week and at least two strength-training sessions are general recommendations. They do not represent a proven amount of activity to prevent knee osteoarthritis. ³² The progression of exercise should be tailored to each person’s health and abilities.

Many people wonder whether certain activities, such as running, can cause osteoarthritis. Research findings are reassuring: in the short term, running is not associated with a worsening of symptoms or visible changes on X-rays ³³, and another review found no clear difference in the prevalence of knee osteoarthritis between runners and people who run less than 8 km per week ³⁴. This body of work is based primarily on observational studies, many of which have significant limitations in how they compare groups. Therefore, they do not prove that running protects against the condition; rather, they show that it has not been linked to an increased incidence of osteoarthritis. See our article “Does Running Cause Osteoarthritis?” to learn more.

Canadian Physical Activity Guidelines

These targets apply to adults aged 18 to 64. Tailored recommendations are available for people aged 65 and older, particularly regarding balance. For people with osteoarthritis, physical activity can improve pain and function on average, though it does not guarantee the absence of symptoms ¹⁷.

Other Prevention Factors

Regular physical activity supports overall health. For people with knee osteoarthritis, exercise can improve strength and reduce pain ³⁵. The leg muscles influence the forces acting on the knee, and osteoarthritis is often accompanied by muscle weakness ³⁶. The program can therefore focus on building strength and addressing activities that are challenging for you, such as standing up from a chair or climbing stairs. Gains in strength do not always translate to the same degree of improvement in every activity.

To deepen your knowledge of osteoarthritis, you can listen to the 'Parle-moi de santé' podcast created by our physiotherapist Alexis Gougeon.

• Écouter l'épisode 15 de Parle-moi de santé sur l'arthrose, sur YouTube

You can also find the podcast on major podcast platforms. For an overview of what physiotherapy is and how it can help you, consult our complete guide to physiotherapy.

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Nos physiothérapeutes ont défini la stratégie de recherche, le plan et le contenu clinique de cet article. Un outil d’IA a soutenu la recherche documentaire et la révision du texte pour assurer une cohérence du contenu et du style d’écriture.