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. Osteoarthritis of the knee is often thought of as normal, age-related “wear and tear” of the joint that gets worse over time and that you can't do anything about. But there are many things you can do for your joints, especially strength and mobility exercises.

The widespread belief that you need to go easy on your knees if you have osteoarthritis is wrong – the opposite is true: Strong muscles stabilize and protect joints. Exercise ensures that the joint cartilage gets nutrients.

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 exercise and painkillers don’t provide enough pain relief. If you’re overweight, losing weight can help.

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 advantages and disadvantages of different treatments and being critical of recommendations. Seeing things realistically can avoid disappointment and unnecessary costs.

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 keep you from sleeping. 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 inner or outer side of the knee may hurt more. If the area under the kneecap is affected, the pain may be most noticeable when getting up and climbing stairs.

In severe osteoarthritis, the joint is also painful at rest. Then the pain is often duller and may be very intense at times, leading to exhaustion and really limiting the everyday activities you can do.

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

Sometimes the knee gets inflamed for a while. That usually causes the knee to feel warm and swell up, and the pain gets worse for a few days.

Some people have osteoarthritis only on the inside or outside of the knee joint. In that case it’s usually the inside that’s affected, and this can be associated with bow-leggedness (varus deformity).

Causes

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 inside 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 can’t repair itself as well as other types of tissue can, so any major damage is lasting.

Osteoarthritis of the knee can develop in three areas:

  • On the inside of the knee joint (medial)
  • On the outside of the knee joint (lateral)
  • Under the kneecap (patellofemoral)

 

Illustration: Front view of the right knee; 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) – as described in the articleFront view of the right knee; 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)

Risk factors

As we age, everyone's joint cartilage wears down a little. But some factors can speed up the wear and tear on the knee joint, increasing the risk of osteoarthritis of the knee. These include:

  • Knee injuries, for example due to meniscus damage, tearing of the anterior cruciate ligament, dislocation of the kneecap, or a bone fracture near the knee joint.
  • Being very overweight: People who have a BMI over 30 are considered to be very overweight (obese). The higher the BMI, the greater the strain on the joints.
  • Repeated major strain on the knee: For example, people who have jobs where they kneel or squat a lot or lift heavy objects are more at risk of osteoarthritis.
  • Anatomy: Having legs of different lengths or knee problems (knock knees or bow legs), for example.

Some people believe that exercise puts additional strain on the knees, increasing wear and tear. But in fact, lack of exercise is more harmful for joints. It weakens muscles, for one thing. Also, the joint cartilage is dependent on exercise: When we walk, for instance, alternating pressure is applied to the cartilage. This causes fluids to be exchanged, providing the cartilage with nutrients.

Prevalence

There are no exact figures on how many people have osteoarthritis of the knee in Germany. According to estimates from other countries, about 4% of all adults are affected. The risk increases with age: About 10-15% of people aged 60 or older have osteoarthritis of the knee. This condition is somewhat more common in women than in men.

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. In some people the symptoms are mild for many years, while in others the osteoarthritis progresses more quickly. A large Dutch study that looked at people with osteoarthritis of the knee several times over the course of five years showed the following:

  • About 60% had moderate pain that got only slightly worse or even improved.
  • About 25% had slight pain that stayed relatively constant.
  • About 10% had severe pain that stayed relatively constant.
  • About 5% had slight pain that got a lot worse over the years.

Sometimes the pain comes and goes in episodes: Then phases with more intense pain are followed by phases with less or no pain. A wrong movement or minor injuries can worsen the osteoarthritis pain for some time. But it often gets better on its own again.

Effects

Osteoarthritis of the knee can cause various changes in the joint over time. After cartilage is lost, the bone surface hardens, and bone spurs known as 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, the cartilage might wear away so much in some places that bone is exposed. Meniscus (cartilage disk) damage, weaker muscles, and loosened ligaments are other possible results of advanced osteoarthritis of the knee. In addition, more joint fluid may be produced, which can also be painful (joint effusion).

Diagnosis

To diagnose osteoarthritis of the knee, the doctor will ask about symptoms like constant or recurrent pain and temporary knee stiffness. They will check the range of motion of the knee joint, look at leg alignment, and check for other possible causes of the pain, like meniscus or ligament damage.

A knee X-ray is usually enough to diagnose osteoarthritis. Special examinations, like an X-ray of the whole leg, computed tomography (CT), or magnetic resonance imaging (MRI) are usually not needed.

Once osteoarthritis has been diagnosed, you don’t have to have regular X-rays for monitoring purposes. Treatment is based on the severity of pain rather than on what can be seen in the X-rays anyway. Further examinations are only needed if osteoarthritis progresses very quickly or other symptoms suggest that it might be a different medical condition.

Other knee scans are also done before implanting an artificial joint (joint replacement). They can be used to help 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.

Despite having osteoarthritis, staying as active as possible helps the joints. Many studies show that regular strength and mobility exercises can relieve pain and improve joint function.

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.

People often recommend wearing well-fitting shoes with shock-absorbent soles. Shoes should support the arch of your foot and leave enough space for your toes. High heels, in contrast, are not helpful.

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 their effect hasn't been well studied yet. One high-quality study showed that unloading shoes that are designed to reduce pressure on the knee didn’t relieve knee pain any better than normal, well-fitting, impact-absorbing shoes when worn for several months.
  • Topical anti-inflammatory painkillers to be applied to the affected joint, like a gel containing diclofenac, can relieve osteoarthritis pain in some people, and are an easy-to-use treatment option with few side effects.
  • Oral anti-inflammatory painkillers like diclofenac, ibuprofen, and etoricoxib are also proven to relieve osteoarthritis pain. Acetaminophen (paracetamol) doesn’t work in osteoarthritis of the knee. Opioids often aren’t any more effective than anti-inflammatory painkillers, but they have more side effects and can be addictive.
  • Acupuncture: Studies suggest that acupuncture can help relieve osteoarthritis of the knee – but no better than placebo acupuncture, where needles are inserted only superficially or in the “wrong” place. Acupuncture treatment of osteoarthritis of the knee is covered by statutory health insurers in Germany.
  • Joint injections: It’s unclear if steroid injections help better than injections of saline solution (a mixture of water and table salt), and there are risks associated with using them. Hyaluronic acid injections are the subject of debate. In the best-quality studies so far, they were hardly any better than saline solutions. Plus, you have to pay for them yourself. Injections with autologous blood products (using processed blood plasma taken from your own body) haven’t been proven to work.
  • X-ray therapy (or orthovoltage therapy) involves treating the joint with low-energy X-rays 6 to 12 times over several weeks. There are no comparative studies on this treatment, so it’s not clear if it helps.
  • In radiosynoviorthesis (RSO), a weak radioactive substance is injected into the knee. Studies haven’t shown it to be effective, and there are reports of complications like bone and joint inflammations.
  • Experts don’t recommend cartilage restoration surgery for osteoarthritis of the knee – it may even make the pain worse and has no proven benefits. This kind of surgery includes, for example, Pridie drilling, microfracture, cartilage grafts, and cartilage and bone grafts.
  • In advanced osteoarthritis of the knee, joint replacement may be an option. 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 patience because it takes time to get used to your new knee.

Many studies have shown that nutritional supplements with chondroitin or glucosamine don’t help. The same is true for endoscopic lavage (washing) of the knee and smoothing of the cartilage (arthroscopy).

Many other products and therapies that don’t have a proven benefit are also offered to treat osteoarthritis of the knee:

  • Herbal supplements like devil’s claw
  • Foods or food extracts, for example based on soy or avocado
  • Ultrasound treatments
  • Transcutaneous electrical nerve stimulation (TENS)
  • Leech therapy
  • A special kind of electrotherapy (“high tone power therapy”)
  • Magnetic field therapy
  • Microwave therapy

Learn more

Research summaries

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.