Understanding Knee Osteoarthritis
Understanding causes, diagnosis and symptoms
Osteoarthritis is a disorder that can affect any moveable joint of the body, for example knees, hips, and hands. It can show itself as a breakdown of tissues and abnormal changes to cell structures of joints, which can be initiated by injury. As the joint tries to repair, it can lead to other problems.
We used to think that osteoarthritis was all about the bones and its coverings (articular cartilage). We now know that it also affects structures like ligaments, nerves and muscles, and there are overall changes to the inflammation process at the joint.
Want to know more about the different parts of a knee joint?
What are the different parts of a joint?
In the knee joint, a coating of tough but smooth and slippery tissue, called cartilage, covers the surface of the bones and helps the bones to move freely against each other. When a joint develops osteoarthritis, part of the cartilage thins and the surface becomes rougher. This means the joint doesn’t move as smoothly as it should.
The body’s repair processes may change the structure and tissues of the joint, but will often allow the joint to work normally and without any pain and stiffness. However, the repair processes don’t always work so well and the changes can sometimes cause or contribute to symptoms such as pain, swelling or difficulty in moving the joint normally.
For example:
- Extra bone may form at the edge of the joint. These bony growths (osteophytes) can sometimes restrict movement or rub against other tissues. In some joints, especially the finger joints, these may be visible as firm, knobbly swellings.
- The lining of the joint capsule (called the synovium) may thicken and produce more fluid than normal, causing the joint to swell.
- Tissues that surround the joint and help to support it may stretch so that after a time the joint becomes less stable.
How common is osteoarthritis?
The percentage of people who have osteoarthritis increases with age and it most commonly affects the knee joint.
Younger and middle-aged people can also get osteoarthritis. Approximately 5% of people between 35 and 54 years of age have osteoarthritis. Many of these people have injured their joint earlier in life.
What causes knee osteoarthritis?
There is not one simple reason why you may have osteoarthritis – it is more likely a combination of things you can’t change e.g. genetics, and things you can potentially change e.g. obesity.
Things you can’t change – hover over the items below to learn more.
AGE
Cartilage is a living tissue that can age and weaken over the years.
SEX
Women get osteoarthritis more often than men. Women get osteoarthritis more often in the knees and hands. Men get osteoarthritis more often in the hips.
GENETICS
You are more likely to get osteoarthritis if someone in your family had it too.
Things you may be able to change – hover over the items below to learn more.
OBESITY
Being overweight or obese puts more load on the joints. Obesity is also associated with changes to inflammation in the body that is linked to development of osteoarthritis.
PHYSICAL ACTIVITY
The knee joints need activity and ‘loading’ to keep the joint healthy. Little or no activity is therefore bad for your knee joints and surrounding muscles.
MUSCLE WEAKNESS
Weak muscles won’t provide proper support to your joint and make it more likely that you will develop osteoarthritis.
What about joint injuries and osteoarthritis?
sports related joint injury
Half of all people with a severe knee injury (meniscus or cruciate ligament injury), often from sports, get osteoarthritis 10-15 years later. Most people hurt their knee as a teenager, which means that they can get osteoarthritis in their 30s.
work or leisure time related injury
Certain physically demanding jobs are linked to a higher chance of knee osteoarthritis. In particular workers in farming or construction jobs that involves lifting heavy loads, frequent climbing or lots of squatting and kneeling are more at risk of osteoarthritis.
How is knee osteoarthritis diagnosed?
Osteoarthritis can be diagnosed by your doctor or another healthcare professional (e.g., a physiotherapist) clinically, by listening to your reported symptoms and without the need for scans (e.g., X-ray).
Typically, osteoarthritis is diagnosed if you:
- Are aged 45 years or older,
- Have activity-related joint pain,
- Have either no morning stiffness or stiffness that lasts no longer than 30 minutes.
X-rays used to be a common way to diagnose osteoarthritis, but now that we understand that they are not needed (and can sometimes even be misleading!).
Want to know more about tests for knee osteoarthritis?
What tests are there for osteoarthritis?
There’s no blood test for osteoarthritis, although your doctor may suggest you have them to help rule out other types of arthritis (e.g., rheumatoid arthritis).
X-rays aren’t usually helpful in diagnosing osteoarthritis – this is a myth!
These are some reasons why X-rays are less commonly used to diagnose osteoarthritis and why the terms ‘bone on bone’ or ‘wear and tear’ are inaccurate and should not be used to describe the condition.
Should I see a specialist?
It’s unlikely that you’ll need to see a specialist to get a diagnosis of osteoarthritis, although your doctor may refer you if there’s some doubt about the diagnosis or if they think there might be additional problems.
Your doctor may refer you if specialist help is needed to manage your osteoarthritis – this might be for physiotherapy, podiatry for foot problems, or occupational therapy, which can help if you’re having difficulty with everyday activities.
If your osteoarthritis becomes severe and is causing long-term problems, your GP may refer you to an orthopaedic surgeon to consider joint surgery or to a pain management programme, if you have already tried the recommended treatment options (exercise and weight and lifestyle management).
Understanding Knee Osteoarthritis Symptoms
Will my osteoarthritis get much worse over time?
In the short-term symptoms can fluctuate up and down.
For most people however, in the medium term, the symptoms of osteoarthritis will not worsen over time. Some people will even improve. A minority will get progressively worse.
One research study reported that over 8 years the majority (85%) of people had no or little progression of their knee osteoarthritis on x-ray. Having had knee surgery in the past and obesity was linked to worsening osteoarthritis on x-ray.
What are the most common symptoms of knee osteoarthritis?
The symptoms of osteoarthritis can significantly affect your function and quality of life. Symptoms may vary for no obvious reason. Or you may find that your symptoms vary depending on what you’re doing.
The good thing is that it is possible to change and improve your symptoms.
The most common symptoms are:
pain / soreness
The presence of pain can be worrying for people with osteoarthritis. We used to think that the pain was linked to ‘damage’ of tissues (for example the cartilage). But we now know that this isn’t true. The level of pain has little to do with worsening of knee osteoarthritis. We now appreciate that pain is a very complex and unique experience that often has very little to do with any structural changes to the joint or the surrounding tissues. This is often very reassuring for people with osteoarthritis as this often acts as a barrier for some people engaging with physical activity or exercise. It’s important to note that things like stress, body weight, lack of sleep and environmental factors all play their part in someone’s pain experience. This is great news as it means there are many things that someone with osteoarthritis can try to influence to reduce the pain they are experiencing. |  |
stiffness
Usually, stiffness occurs when someone stays in a position for a long period of time. For example, people will often get stiffness when they first get up in the morning or after they have sat down watching TV for an hour or so.
This should not cause concern and should ease when you start to move your leg/knee.
If you are performing activities like watching TV, try to straighten and bend your knee regularly, or split your time doing sedentary activities with more physically active tasks.
crepitus
Many people with and without knee conditions complain of noisy joints. Noises can vary from grinding to clicking and cracking. The noises joints make are commonly referred to as ‘crepitus’ by healthcare professionals. We know from research that these noises are sometimes concerning for people with osteoarthritis, and they are fearful that they are causing damage. But generally, these sounds are completely normal and should not cause concern. |  |
swelling
People often think that osteoarthritis just affects the cartilage. But actually – osteoarthritis affects many structures at the knee joint (including bone, muscles, ligaments etc.). In osteoarthritic joints, there is a constant cycle of degeneration and regeneration. Sometimes this may cause bony enlargements to occur.
It’s important to note that the extent of bony enlargement is not necessarily an indication of how severe your knee osteoarthritis is.
pain / soreness
The presence of pain can be worrying for people with osteoarthritis. We used to think that the pain was linked to ‘damage’ of tissues (for example the cartilage). But we now know that this isn’t true.
The level of pain has little to do with worsening of knee osteoarthritis.
We now appreciate that pain is a very complex and unique experience that often has very little to do with any structural changes to the joint or the surrounding tissues. This is often very reassuring for people with osteoarthritis as this often acts as a barrier for some people engaging with physical activity or exercise.
It’s important to note that things like stress, body weight, lack of sleep and environmental factors all play their part in someone’s pain experience. This is great news as it means there are many things that someone with osteoarthritis can try to influence to reduce the pain they are experiencing.
stiffness
Usually, stiffness occurs when someone stays in a position for a long period of time. For example, people will often get stiffness when they first get up in the morning or after they have sat down watching TV for an hour or so.
This should not cause concern and should ease when you start to move your leg/knee.
If you are performing activities like watching TV, try to straighten and bend your knee regularly, or split your time doing sedentary activities with more physically active tasks.
crepitus
Many people with and without knee conditions complain of noisy joints. Noises can vary from grinding to clicking and cracking. The noises joints make are commonly referred to as ‘crepitus’ by healthcare professionals.
We know from research that these noises are sometimes concerning for people with osteoarthritis, and they are fearful that they are causing damage.
But generally, these sounds are completely normal and should not cause concern.
swelling
People often think that osteoarthritis just affects the cartilage. But actually – osteoarthritis affects many structures at the knee joint (including bone, muscles, ligaments etc.). In osteoarthritic joints, there is a constant cycle of degeneration and regeneration. Sometimes this may cause bony enlargements to occur.
It’s important to note that the extent of bony enlargement is not necessarily an indication of how severe your knee osteoarthritis is.
Other Pain Resources
Clinical recommendations on how best to manage your pain can be found in the next section, Understanding Treatments.
For other helpful resources on pain management, please see Patient Resources and Supports.
Now you know more about your condition, let’s learn more about the different treatment options.
The information in this website page was informed by the following sources/references:
Scientific Publications
- Blackburn, S., Research User Group, Rhodes, C., Higginbottom, A., & Dziedzic, K. (2016). The OARSI standardised definition of osteoarthritis: A lay version. Osteoarthritis and Cartilage, 24(S1), S192 -S192. https://doi.org/10.1016/j.joca.2016.01.379
- French HP, Galvin R, Horgan NF, Kenny RA. Prevalence and burden of osteoarthritis amongst older people in Ireland: findings from The Irish LongituDinal Study on Ageing (TILDA). Eur J Public Health. 2016 Feb;26(1):192-8. doi: 10.1093/eurpub/ckv109.
- French SD, Bennell KL, Nicolson PJ, Hodges PW, Dobson FL, Hinman RS. What do people with knee or hip osteoarthritis need to know? An international consensus list of essential statements for osteoarthritis. Arthritis care & research. 2015;67(6):809-816.
- Mobasheri A, Batt M. An update on the pathophysiology of osteoarthritis. Annals of physical and rehabilitation medicine. 2016;59(5-6):333-339.
Patient Websites/Resources
- TREK ‘My Knee’ education and self-management toolkit. La Trobe University. https://myknee.trekeducation.org/
- Versus Arthritis. https://www.versusarthritis.org/about-arthritis/conditions/osteoarthritis/
Clinical Guidelines
- National Clinical Guideline Centre (UK). National Institute for Health and Clinical Excellence: Guidance. Osteoarthritis in over 16s: diagnosis and management. NICE guideline [NG226]. Published: 19 October 2022. https://www.nice.org.uk/guidance/ng226