Osteoarthritis of the knee (gonarthrosis)

If the knee initially feels stiff after rests and hurts during movement, osteoarthritis may be behind it. Osteoarthritis of the knee (also known as knee arthrosis, knee arthritis or gonarthrosis) occurs when the articular cartilage in the knee becomes thinner and therefore provides less protection for the knee.

The common perception that it is necessary to rest the knee for osteoarthritis is false – on the contrary, well-trained muscles stabilize and protect the joints. Exercise ensures that the articular cartilage is supplied with nutrients. Therefore, the most important treatment involves types of movement and exercise to keep the cartilage and joint in good condition. For those who are overweight, losing a little weight can relieve strain on the knee.

If osteoarthritis of the knee is already advanced and severely impairing everyday activities and quality of life, a joint replacement may be considered – especially if the symptoms cannot be sufficiently relieved by exercise or pain medication.

Osteoarthritis of the knee typically begins with knee pain that initially only occurs with strain. If the osteoarthritis progresses over time, the pain becomes more frequent and severe. It can then also occur during rest or at night and disturb the sleep. Furthermore, other symptoms like stiff joints can appear. Many people with osteoarthritis of the knee suffer joint pain, especially towards evening or in the morning.

Depending on which part of it is affected, pain can occur on the inside or outside of the knee. If the area under the kneecap is affected, pain occurs in particular when standing up and climbing stairs.

In the case of severe osteoarthritis, the pain occurs even during rest. It then often feels more nagging and can be temporarily very severe, lead to exhaustion and seriously limit everyday life.

The knee joint can also become stiffer and sensitive to pressure. If it is moved less, that weakens the muscles and ligaments. This can make the knee feel unstable.

For some people, the osteoarthritis triggers acute episodes lasting several days. During these episodes, the pain suddenly becomes more intense and may feel like shooting, pulsing or burning in the knee. The knee may also temporarily swell up, become stiffer and feel hot. Acute episodes can be particularly aggravating because they are difficult to predict.

The knee joint connects the femur and lower leg bones and the kneecap. The epiphyses and inside of the kneecap are covered with cartilage. A healthy cartilage is a smooth sliding surface that makes low-friction movement in the joint possible. Osteoarthritis develops when the cartilage softens, disintegrates and thins. Cartilage cannot regenerate itself as well as other tissue. Once major damage has occurred, it therefore remains.

Osteoarthritis of the knee can occur in three areas of the knee:

• on the inside of the knee joint (medial)
• on the outside of the knee joint (lateral)
• under the kneecap (patellofemoral)

Everyone’s articular cartilage wears out somewhat as they age. People commonly refer to this as “wear and tear” on the joints. However, this phrase is misleading as it gives the impression that the joints are “worn down” during normal use. This is not the case at all. In fact, cartilage in the joints is naturally broken down and rebuilt all the time. And movement is needed to promote these rebuilding process and blood supply to the joints.

Causes of damage to the cartilage include:

• Knee joint injuries: for example, due to meniscal damage, a tear in the anterior cruciate ligament, a dislocation of the patella or a bone fracture close to the knee joint
• Severe overweight (obesity): people who have a body-mass index (BMI) over 30 are considered obese. The higher the BMI, the greater the strain on the joints.
• frequent severe strains on the knee: whoever has to kneel, crouch or do heavy lifting in their job for instance has a higher risk of osteoarthritis.
• Anatomy: for example, legs of differing length or defective knee positions (knock knees or bow legs)

It is not known precisely how many people in Germany have osteoarthritis of the knee. According to estimates from other countries, about 4% of all adults are affected.

Prevalence increases with age. About 10% to 15% of people over 60 have osteoarthritis of the knee, with women being slightly more likely to be affected than men.

Osteoarthritis does not invariably mean that the knee is so damaged at one time or another that a joint replacement is required. Many people manage well in day-to-day life despite the discomfort.

The progression of osteoarthritis of the knee cannot be predicted with certainty. Many people only have minor discomfort for many years, while for others the osteoarthritis advances more quickly. A major Dutch study in which people with osteoarthritis of the knee were repeatedly examined for 5 years revealed, that:

• about 60% had moderate pain that only slightly increased or even subsided
• around 25% had slight pain that remained at a relatively stable level over the period
• about 10% percent had severe pain that remained at a relatively stable level over the period
• approximately 5% had mild pain that increased considerably over the years

The pain can also occur periodically, alternating between phases of more severe pain and phases with little to no pain. Awkward movements or minor injuries can temporarily increase arthritis pain. But this pain often subsides again by itself.

To determine osteoarthritis of the knee, the doctor asks about symptoms such as recurrent or persistent pain and temporary stiffness in the knee. They check the knee joint’s range of movement, observe the leg posture and determine whether there are other possible causes for the pain, such as damage to the meniscus or ligaments.

An X-ray of the knee joint is usually sufficient to determine osteoarthritis. More specific examinations, such as an X-ray of the entire leg, computed tomography (CT) or magnetic resonance imaging (MRI) are not usually necessary.

If the diagnosis is clear, no regular X-ray checks are required. In any case, the treatment is geared toward the symptoms and not based on what is visible in the X-ray images. Other examinations are only a good idea if the osteoarthritis advances unexpectedly quickly or additional symptoms appear that might indicate another disease.

Additional images of the knee joint are made before the insertion of an artificial joint (joint replacement). They help with planning of the operation.

There are various options for treating osteoarthritis of the knee. Which ones are considered depends, for example, on how far advanced the osteoarthritis is, whether there are any accompanying conditions and what is expected from the treatment.

Staying active in spite of osteoarthritis is good for the joints. Many studies have demonstrated how regular strengthening and flexibility exercises relieve pain and can improve joint function.

For those who are overweight, losing weight can relieve strain on the joints. As studies have shown, a weight reduction of more than 5% can improve mobility and relieve joint pain to some degree.

Experts often recommend wearing shoes that fit well and have cushioned soles. They should support the arch of the foot and provide enough room for the toes. Shoes with high heels on the other hand should be avoided.

You can find more detailed information, for example about how to strengthen your knees, at gesundheitsinformation.de.

There are moreover numerous treatment approaches for osteoarthritis of the knee:

• Arch supports, orthoses (devices worn to support the knee joints) and offloading shoes are low-risk options to try. However, there is currently a lack of good research about their effect. In a significant study, a special offloading shoe failed to relieve knee discomfort over several months any more effectively than regular, well-fitting shoes with cushioned soles.
• Non-steroidal anti-inflammatory drugs for application to the affected joint such as gel with diclofenac can relieve osteoarthritic pain in many people and are a simple treatment option with few side effects.
• Non-steroidal anti-inflammatory drugs for ingestion like diclofenac, ibuprofen and etoricoxib can also demonstrably relieve osteoarthritic pain. Paracetamol is not effective with osteoarthritis of the knee.
• Opioid painkillers are often no more effective than anti-inflammatory drugs. They also have more side effects and can be addictive.
• Acupuncture: studies indicate that it can alleviate osteoarthritis of the knee – however not better than a so-called fake acupuncture in which the needles are only placed superficially or at the “wrong” site.
• Injections into the joint: cortisone injections can relieve symptoms for up to 8 weeks but can cause damage to the cartilage in the long term with repeated use. Injections with hyaluronic acid are controversial. In the most important studies conducted to date, they proved to be no more effective than saline solutions. They are also not covered by health insurance. The benefits of autohemotherapy – where the joint is injected with a mixture containing blood plasma from the patient’s own blood – have yet to be verified.
• A joint replacement may be considered in the case of advanced osteoarthritis of the knee. An artificial knee joint (prosthesis) significantly relieves the symptoms of advanced osteoarthritis of the knee for most people. After the operation, active rehabilitation is important, as well as patience while adjusting to the new knee.
• A corrective knee osteotomy is sometimes considered as an alternative to knee replacement. This surgical procedure involves correcting unevenness in the cartilage on one side of the knee.
• With X-ray stimulation therapy (also called orthovoltage therapy), the joint is treated 6 to 12 times with low-dose X-ray radiation over several weeks. There are currently no comparative studies about this treatment. Whether it helps is therefore unclear.
• With radiosynoviorthesis (RSO), a low-dose radioactive substance is injected into the knee joint. Studies have failed to demonstrate any benefit and, moreover, there are some reports of complications such as bone and joint inflammations.
• Experts advise against surgical procedures to treat the cartilage – these can sometimes make the symptoms even worse and have no proven benefits. Such surgical procedures include for instance Pridie drilling, microfracture and cartilage cell or cartilage-bone transplants.
• Endoscopic knee irrigation and cartilage shaving (arthroscopy): Several studies have shown that this is of no benefit to those with osteoarthritis of the knee.

The decision aid from gesundheitsinformation.de can help you decide for or against a joint replacement.

In addition, many other products and therapies without proven benefits are offered for the treatment of osteoarthritis of the knee. These include:

• duloxetine
• herbal preparations like rampion or boswellia
• food supplements with chondroitin or glucosamine
• foods or food extracts, e.g. based on soybean, avocado or curcumin
• ultrasound therapies
• transcutaneous electric nerve stimulation (TENS)
• leech therapy
• high-frequency therapy
• magnetic field therapy
• microwave therapy