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. These injections can relieve the symptoms – but only temporarily, and not much more effectively than injections with a saline (salt) solution. There is not enough research on treatment using your own blood or stem cells.

Injections into the joint space of the knee are a common treatment. They 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 it into its components in a centrifuge. Certain growth factors and chemical messengers are then taken out of the blood and turned into a concentrated solution.

All knee injections carry a risk of infecting the knee joint. This can happen if there are germs on the needle that is used for the injection. Joint infections are very rare, but they can cause serious problems. Because of the potential risk of infection, medical societies recommend getting injections only from experienced doctors who follow hygiene standards, for instance by properly disinfecting the skin before giving the injection.

It’s worth weighing the pros and cons of joint injections, not only because of possible side effects. The costs of steroid injections are covered by German statutory health insurers. But injections containing hyaluronic acid or other drugs are considered to be "individual health care services" (“IGeL”), which you have to pay for yourself.

What do studies on steroid injections show?

An independent group of scientists from the Cochrane Collaboration analyzed 27 studies on steroid injections for osteoarthritis of the knee. The outcome: The injections might reduce osteoarthritis symptoms for several weeks in just over 10 out of 100 people.

But the scientists couldn't draw any conclusions about the effectiveness of steroid injections because only one of the studies was of high enough quality.

All knee injections carry a risk of infection. This risk is slightly higher with steroid injections than with other drugs because steroids weaken the immune response within the joint. Repeated steroid injections over a long time period can also weaken the joint cartilage. But it's not clear whether this really affects the health of your knee.

Other possible side effects include pain and swelling at the injection site. If someone has several injections, the skin at the injection site can also become permanently lighter-colored. In the days after treatment, muscles and ligaments may be slightly weakened.

The German Society of Orthopedics and Orthopedic Surgery (DGOOC) recommends them for the short-term treatment of severe knee pain when other effective treatments don't work well enough. Here, too, it’s important to use the lowest possible dose. It is recommended that doctors wait twelve weeks between giving one steroid injection and the next.

What do studies on hyaluronic acid show?

Hyaluronic acid is a substance in the body that acts as a “lubricant” in the joints. Since the hyaluronic acid that is naturally found in joints is broken down more quickly in osteoarthritic joints than in healthy joints, hyaluronic acid solutions were developed to balance out the loss. 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.

Many studies have examined the effectiveness of hyaluronic acid injections. In the best-quality studies done so far, they were only slightly more effective than injections with saline solution (a mixture of salt and water). But there are many different hyaluronic acid products that differ in things like their chemical composition. It’s possible that only some of these products work.

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. Like all knee injections, hyaluronic acid injections can cause problems like infections in the joint, but that very rarely happens. You can find more 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?

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.

To get injections with your own blood, several milliliters of your blood are drawn from a vein. Blood plasma and platelets are separated using a centrifuge in the doctor’s office. This “platelet-rich plasma,” also abbreviated as PRP or 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 promote inflammations, for example.

What is known about injections with your own stem cells?

There has been some initial research on treatment with your body’s own stem cells. Stem cells can develop into different types of body cells, depending on where 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 inflammation in the knee and encourage the growth of new cartilage tissue. But laboratory tests show that few stem cells survive or stay in the joint after being injected.

There are no high-quality studies on the effectiveness of stem cell treatment for osteoarthritis of the knee. So it’s not clear whether it could help people with this condition.