Do knee injections help?

Photo of a woman laying floorboards while kneeling
PantherMedia / Arne Trautmann

Sometimes osteoarthritis of the knee is treated with steroid or hyaluronic acid injections into the knee. Steroid injections can relieve the symptoms for several weeks. Hyaluronic acid has no proven benefit. There is not enough research on treatment using your own blood or stem cells.

Injections into the space in the knee joint typically contain a corticosteroid drug (a “steroid”) or hyaluronic acid. Some doctor's offices and hospitals also offer injections with processed blood plasma (treatment with your own blood). This involves taking blood and separating the different parts in a centrifuge. Certain and chemical messengers are then taken out of the blood and turned into a concentrated solution.

In Germany, the costs of some steroid injections are covered by the statutory health insurers. Injections containing hyaluronic acid or other drugs are considered to be "individual health care services" (“IGeL”), which you have to pay for yourself. Only steroid injections have been proven to temporarily relieve the symptoms of osteoarthritis of the knee.

All of the injections can lead to a joint , although the risk is low. This can happen if there are germs on the needle that is used for the injection. It occurs in about 4 out of 10,000 injections. A joint can lead to serious complications. This risk of joint infections is probably slightly higher with steroid injections than with other drugs because steroids weaken the immune response within the joint.

Because of the potential risk of , medical societies recommend only getting injections from experienced doctors who follow hygiene standards, for instance by properly disinfecting the skin before giving the injection.

How well do steroid injections work?

Several international groups of researchers from Switzerland, Finland, the United States and Canada analyzed studies on steroid injections in the treatment of osteoarthritis of the knee. Their analysis showed that steroid injections can relieve the symptoms for up to eight weeks in 10 to 20 out of 100 people. The results also suggest that

  • the injections do not have any benefit if you are doing exercise therapy at the same time.
  • doing physical therapy exercises at home (after being shown how to do them properly) can help more over the long term than steroid injections can.
  • repeated steroid injections over a long period of time can weaken the cartilage in the joint.

The possible side effects of steroid injections include pain and swelling where the injection is given. If someone has several injections, the skin at the injection site can also become permanently lighter in color. The muscles and ligaments may be weaker in the days after the treatment.

The German Society of Orthopedics and Orthopedic Surgery (DGOOC) recommends steroid injections for the short-term treatment of severe knee pain when other effective treatments don't provide enough relief. Some experts recommend waiting at least twelve weeks between each injection.

If you plan to have an artificial knee joint implanted, no steroids should be injected into the joint for three months before the surgery. Steroid injections increase the risk of infecting the new joint.

What do studies on hyaluronic acid show?

Hyaluronic acid is a substance in the body that acts as a lubricant in the joints. Injections of this substance are meant to help increase the amount of hyaluronic acid in the joint, where it occurs naturally. These injections are sometimes described as having a cartilage-restoring effect. But that’s actually misleading: There’s no scientific proof that hyaluronic acid can restore cartilage.

While steroid injections are supposed to help in the short term, hyaluronic acid is claimed to have a long-lasting effect. But several analyses by independent groups of researchers haven't found them to have any clear benefit. In the best-quality studies, hyaluronic acid injections weren't any better than a placebo (injections of salt water).

Different experts have different recommendations when it comes to hyaluronic acid: Some say it's best not to use it, while others see it as an alternative – especially for people who can’t take painkillers or whose treatment with painkillers isn't effective enough.

Hyaluronic acid injections can lead to temporary pain, redness and swelling in the joint. People living in Germany can find more useful information on the website www.IGeL-Monitor.de, provided by the medical commission of the German statutory health insurance association (MDS).

Can treatment with autologous blood help?

To get injections with a substance made from your own blood, several milliliters of your blood are taken from a vein. Blood plasma and platelets are separated using a centrifuge in the doctor’s office. This “platelet-rich plasma” (PRP), also known as "autologous conditioned plasma" (ACP), is then injected into the knee joint. Growth factors that are released by the platelets are thought to stimulate the recovery of the joint cartilage. But platelet-rich plasma also contains substances that can make inflammations worse, for example.

Autologous blood injections (using your own blood) haven't yet been proven to reduce the symptoms of osteoarthritis of the knee. There are no good-quality studies in this area.

The German Society for Orthopedics and Orthopedic Surgery (DGOOC) currently does not recommend the use of platelet-rich plasma injections. The Osteoarthritis Research Society International (OARSI) and the American College of Rheumatology (ACR) even advise against their use in their current guidelines.

What is known about injections with your own stem cells?

Stem cells can develop into different types of body cells, depending on what part of the body they come from. For example, stem cells can be taken from fat tissue and grown in a laboratory.

The hope is that these cells will reduce in the knee and encourage the growth of new cartilage tissue. But laboratory tests have shown that few stem cells survive or stay in the joint after being injected.

There is still a lack of good-quality research on the effectiveness of stem cell treatments in osteoarthritis. So it's not clear whether they can help in people with osteoarthritis of the knee. Medical societies also currently advise against the use of autologous stem cells (taken from your own body).

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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

Authors/Publishers:

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

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