A doctor may suggest injections as a treatment for osteoarthritis (OA), which involves the erosion of joint cartilage and bone. It also leads to pain and can affect function and mobility.

When knees are sore, stiff, and swollen from OA, several treatment options are available. They include exercise, weight management, and over-the-counter pain medication. However, if these treatments do not resolve symptoms, injections may help provide relief.

Both the American College of Rheumatology and the Arthritis Foundation strongly recommend using glucocorticoid injections to treat pain and inflammation due to OA of the knee.

Some doctors may offer other options, such as hyaluronic acid or stem cell injections. However, current guidelines do not recommend these, as there is not enough evidence to show that they are safe and effective.

In this article, we explain what to expect from corticosteroid injections. We also look briefly at several other types of injection that may be available but do not yet have approval.

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Steroid medicines act in a similar way to the hormone cortisol. Cortisol works on the immune system to reduce inflammation throughout the body, also serving to relieve pain.

Injections for OA are usually intra-articular, which means the doctor injects them into the joint. They can provide relief for moderate to severe pain, and the effect may last several months.

Five different corticosteroid medicines have approval from the Food and Drug Administration (FDA) to treat OA. They are:

  • methylprednisolone acetate
  • triamcinolone acetate
  • betamethasone acetate and betamethasone sodium phosphate
  • triamcinolone hexacetonide
  • dexamethasone

In 2018, the FDA has approved an extended-release injection of triamcinolone acetonide known as Zilretta. A person can have it only once, but its anti-inflammatory effects may last longer than those of other types.

People will need to visit a doctor for the injection. Doctors sometimes use ultrasound to guide the placement of the needle into the space around the joint.

The doctor may also use a local anesthetic with the injection, which will provide immediate relief. The steroid should start taking effect within a few days. The effect will last from several weeks to several months.

Steroid injections may not help everyone. In some people, corticosteroid injections can help relieve pain and improve movement in the joint. Others do not find any pain relief from these shots. In addition, long-term use may have adverse effects. For this reason, doctors prefer other options, if possible.

Limited use of corticosteroid shots is likely safe. However, there may be long-term effects if people use them too often.

Possible side effects of the injection include:

  • a worsening of joint pain in the first 24 hours
  • changes in skin color near the injection site
  • nerve damage
  • changes in menstruation
  • mood changes

Experts recommend avoiding putting stress on the joint for the first 14 days after an injection. They also suggest following a healthcare professional’s advice on exercise after that.

If a person has concerns about the adverse effects of an injection, they should contact a doctor.

Long-term, repeated steroid use can also produce adverse effects. According to the Arthritis Foundation, these may include:

If pain returns, a person may not be able to have another shot right away. Doctors only recommend receiving corticosteroid injections once every 3–4 months.

Receiving shots too frequently can increase the risk of adverse effects, such as damage to soft tissues in the knee.

If injections every few months are not frequent enough to relieve the pain, another type of treatment may be necessary.

Sometimes, doctors offer other types of injections, such as:

While some of these may hold promise as future treatments, guidelines currently advise against using them for OA of the knee.

Reasons include:

  • a lack of evidence that they are beneficial
  • insufficient research to support their use
  • a lack of standards regulating their use, which means a person cannot be sure what is in the injection

These injections may not be helpful, and they could be unsafe.

People who think they might have OA of the knee should ask a doctor whether knee injections are an appropriate next step.

Corticosteroid injections can help, but the effects are not permanent. As these medications wear off, it will likely be necessary to repeat the injection. However, a doctor will not usually repeat a steroid injection until after 3–4 months, due to the risk of side effects.

Other experimental injections, such as PRP and stem cell injections, are under examination. However, these are not yet mainstream treatments. Current guidelines do not recommend using them.