Osteoarthritis of the knee

At a glance

  • In osteoarthritis of the knee, the layer of cartilage that protects the knee joint thins out.
  • This causes pain and means you can't move your knee as much.
  • Certain exercises and inflammation-reducing painkillers can help. If you're overweight, losing weight can help too.
  • Steroid injections can relieve the symptoms for a few weeks. But they damage the cartilage over the long term.
  • Other types of injections haven't been proven to work.
  • If osteoarthritis is advanced and very painful, joint replacement surgery may be considered.

Introduction

Woman doing Nordic walking
PantherMedia / vladvitek

If your knee feels stiff for a while after resting and hurts when you move it, you may have osteoarthritis. In osteoarthritis of the knee, the cartilage covering the joint surfaces thins out and provides less protection.

The widespread belief that you need to go easy on your knees if you have osteoarthritis is wrong – the opposite is true: Movement strengthens the muscles that stabilize and protect the joints. It also ensures that the cartilage in the joint gets nutrients. So a key part of treatment is doing exercises and sports that keep the cartilage and joint fit. If you are overweight, even losing a little bit of weight can already have a positive effect on your knee.

Anti-inflammatory (inflammation-reducing) painkillers can provide relief, particularly during acute phases when/where the symptoms are worse. If osteoarthritis of the knee has progressed, interferes with your daily routines, and reduces your quality of life, joint replacement surgery may be an option – especially if other treatments don’t help enough.

Many medications and techniques that are claimed to help in osteoarthritis haven’t been proven to be effective, and may even be harmful. So it’s worth carefully weighing the pros and cons of different treatments and not trying out everything that's on offer. Having realistic expectations prevents disappointment and saves money.

It's also important to know that the results of x-ray exams and other imaging techniques don't affect the choice of treatment much. The most suitable treatment will depend on your symptoms and personal situation.

Symptoms

Osteoarthritis of the knee typically starts with knee pain that only occurs when you put pressure on the joint. If the osteoarthritis gets worse over time, this pain gets stronger and more frequent. You may even feel it when you rest the joint or at night, and it may stop you from sleeping properly. You might have other symptoms too, like joint stiffness. Some people’s joints are especially painful in the evenings or mornings.

Depending on the part of the knee that is affected, the left or right side of the knee may hurt more. If the area under the kneecap is affected, it mainly hurts when you do things like getting out of a chair and climbing stairs.

In severe osteoarthritis, the joint also hurts when at rest. Then the pain is often duller and may be very intense at times, lead to exhaustion and really limit what you can do in everyday life.

The knee joint can also become stiffer and more tender to the touch. Moving it less weakens the muscles and ligaments around it, making your knee feel unstable.

Some people have acute flare-ups of osteoarthritis in their knee. Then the pain suddenly gets worse and feels more like a stabbing, throbbing or burning sensation. The knee might become swollen, stiff and warm. This is sometimes referred to as an active phase of the disease. The symptoms that occur during flare-ups usually go away again within a few days. Flare-ups often come without any warning. This can make it particularly hard to cope with them.

Some people have osteoarthritis only on one side of the knee joint. In that case, the side of the knee facing the other knee is usually affected.

Osteoarthritis of the knee can develop in three areas:

  • On the side of the knee joint facing the other knee (medial)
  • On the side of the knee joint facing away from the other knee (lateral)
  • Under the kneecap (patellofemoral)

Illustration: Front view of the right knee without the kneecap; on the left with osteoarthritis on one side of the knee joint (medial); on the right with advanced osteoarthritis on both sides of the knee joint (medial and lateral)

Front view of the right knee without the kneecap; on the left with osteoarthritis on one side of the knee joint (medial); on the right with advanced osteoarthritis on both sides of the knee joint (medial and lateral)

Causes and risk factors

The knee joint connects the thighbone (femur), shinbone (tibia), calf bone (fibula), and kneecap (patella) with each other. The ends of the bones and the inner side of the kneecap are covered with cartilage. Healthy cartilage has a smooth gliding surface that allows low-friction movement. Osteoarthritis develops if the cartilage softens and becomes cracked and thinner. Cartilage damage can be caused by various things, including the following:

  • Knee injuries, for instance due to meniscus damage, a torn anterior cruciate ligament, dislocation of the kneecap, or a bone fracture near the knee joint.
  • Being very overweight: People with a body mass index () over 30 have a higher risk of osteoarthritis. Being overweight puts more strain on the knee and can also make joint inflammation worse.
  • Anatomy: Having legs of different lengths or knee problems (knock knees or bow legs), for example.

People often refer to osteoarthritis as "wear and tear" of the joints. This is misleading because it suggests that that osteoarthritis can't be stopped and that the joint is worn down through normal use. But that's not the case! In fact, the tissue in our joints is constantly being broken down and replaced. The joint needs to be moved in order to help it make the new tissue. This makes sure that the knee gets enough blood. Movement is also important for the cartilage. Like a sponge, cartilage releases waste products when squeezed and absorbs nutrients from the joint fluid when released again. So specific types of exercises and sports like brisk walking or cycling are good for your cartilage and joints even if you have osteoarthritis.

Prevalence

In Germany, about 4% of all adults have osteoarthritis of the knee. It is more common in people over the age of 40.

Outlook

Having osteoarthritis doesn’t necessarily mean that the knee will eventually become so damaged that you’ll need a joint replacement. Many people manage their daily lives well despite the symptoms.

It's hard to accurately predict how osteoarthritis will continue to develop over time. A lot of people only have mild symptoms for many years, and in others they progress more quickly. Sometimes the symptoms even improve over time.

A review of studies involving more than 7,000 participants showed the following over five to eight years:

  • The pain stayed about the same in around 85% of the participants.
  • It got worse in about 7% of the participants.
  • And it got better in about 8% of the participants.

Even though osteoarthritis of the knee usually progresses gradually and is often stable for years, it can keep getting worse for a few days or weeks at a time.

About 40% of people with osteoarthritis have acute flare-ups, especially if they have already had the disease for a long time. Most of them have about one flare-up per month, but the frequency varies a lot.

How much osteoarthritis affects you depends on factors other than the condition of your knee joint. These include your individual attitude, your social and work life, your lifestyle and emotional aspects like fears, worries and stress. They can all affect how the symptoms feel, how severe they are, and how you cope with them.

Effects

Advanced osteoarthritis of the knee can cause changes in the knee joint. After cartilage is lost, the bone under the cartilage thickens and hardens, and bone spurs called osteophytes can form on the edges of the bone. They can limit the joint’s range of motion and irritate tendons and ligaments, causing pain.

In very advanced osteoarthritis, parts of the cartilage may be completely gone. Then the bones of the joint rub directly against each other.

Osteoarthritis of the knee can also lead to meniscus (cartilage disk) damage, weaker muscles, and loose ligaments. There might be too much fluid in or around the joint as well, which can be painful.

Diagnosis

A doctor can usually diagnose osteoarthritis of the knee based on the typical symptoms. They will ask how long you have had the pain, what it feels like, and whether there are other symptoms such as stiffness in the knee in the morning. Then the doctor will check how far you can move your knee, feel the knee and the joint space, and examine the muscles.

Imaging techniques such as x-ray, ultrasound or MRI () scans can’t tell us much about the symptoms of osteoarthritis. Some people have big changes in their joint but hardly any symptoms, while others have severe symptoms but a healthy-looking joint. Studies also show that people who have no symptoms often have visible changes in their knee joint.

  • About 20% of people over the age of 40 have meniscus tears or damage that are visible in MRI scans.
  • Around 40% have changes in their cartilage.
  • And about 40% have osteophytes or changes in their bones.

If these types of changes are wrongly thought to be causing the symptoms, it may result in unnecessary anxiety and ineffective surgery. The treatment of the symptoms should be based on your symptoms and individual situation, and not what can be seen in scans.

Imaging scans or blood tests can be useful if your doctor thinks that you might have another disease like rheumatoid arthritis or gout, or to see whether a bone has been broken after a fall or accident. Knee scans are also done before implanting an artificial joint (joint replacement), in order to plan the surgery.

Treatment

There are various treatment options for osteoarthritis of the knee: Which ones are worth considering depends on things like how advanced it is, whether you have any other medical conditions, and what you expect from the treatment.

Even if you have osteoarthritis, staying as active as possible is good for your joints. Many studies show that regularly doing strength and mobility exercises can relieve pain and improve joint function. Yoga and tai chi are options as well.

If you’re overweight, losing weight can reduce stress on the joints. Studies have shown that weight loss of more than 5% can improve the range of motion and slightly relieve joint pain. For instance, that would mean losing at least 5 kilograms (11 pounds) if you weigh 100 kilograms (220 pounds).

Well-fitting shoes with thicker and sturdy soles that provide support have also been proven to help. The shoes should have plenty of room for your toes as well. Shoes with thin, flexible soles such as moccasins or “barefoot” shoes and high heels are less suitable.

There are also many treatment options for osteoarthritis of the knee:

  • Insoles, orthotics, and special “unloading” shoes are low-risk options that can be tried out, but there's a lack of good research on their effect. One high-quality study showed that special "unloading" shoes that are designed to reduce pressure on the knee weren’t any better than normal, well-fitting, impact-absorbing shoes.
  • Applying creams or gels containing anti-inflammatory painkillers such as diclofenac to the joint can relieve osteoarthritis pain in some people. They are a simple treatment option with a low risk of side effects.
  • Oral anti-inflammatory painkillers that are swallowed (like diclofenac, ibuprofen, and etoricoxib) have also been proven to relieve osteoarthritis pain. Acetaminophen (paracetamol) doesn't help in osteoarthritis of the knee. Opioids often aren’t any more effective than anti-inflammatory painkillers, but they have more side effects and can lead to dependency.
  • Acupuncture: Studies suggest that can help to relieve osteoarthritis of the knee – but no better than fake (placebo) , where needles are inserted only superficially or in the “wrong” place. In Germany, treatment of osteoarthritis of the knee is covered by statutory health insurers.
  • Injections into the joint: Steroid injections can relieve the symptoms for up to eight weeks, but may damage the cartilage when used repeatedly for a long time. Injections of hyaluronic acid, blood taken from your own body (platelet-rich plasma) or stem cells have not been shown to work.
  • In advanced osteoarthritis of the knee, joint replacement may be considered. An artificial knee joint can considerably relieve the pain of advanced osteoarthritis in most people. After surgery, it’s important to have active rehabilitation treatment – and to be patient because it takes time to get used to your new knee.
  • A treatment called corrective osteotomy is sometimes considered as an alternative to joint replacement. It involves the correction of misalignments that put too much strain on one part of the knee and are responsible for the osteoarthritis.

There are also many other products and therapies for osteoarthritis of the knee that don’t have a proven benefit. These include:

  • Duloxetine
  • Plant-based products such as devil’s claw or frankincense
  • Dietary supplements containing chondroitin or glucosamine
  • Foods or food extracts, for example based on soy, avocado or turmeric
  • Ultrasound treatments
  • Transcutaneous electrical nerve stimulation (TENS)
  • Leech therapy
  • A special kind of electrotherapy (“high tone power therapy”)
  • Magnetic field therapy
  • Microwave therapy
  • X-ray therapy (orthovoltage therapy)
  • Radiosynoviorthesis (RSO)
  • Endoscopic lavage (washing) of the knee and smoothing of the cartilage (arthroscopy)

Further information

When people are ill or need medical advice, they usually go to see their family doctor first. Read about how to find the right doctor, how to prepare for the appointment and what to remember.

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IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on August 24, 2021
Next planned update: 2024

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Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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