A doctor may suggest injections as a treatment for osteoarthritis, an inflammatory condition of joint cartilage and bone.

When knees are sore, stiff, and swollen from osteoarthritis, several treatment options are available.

Treatment for osteoarthritis (OA) of the knee may start with non-medicinal interventions, such as exercise or weight loss. Another option is over-the-counter (OTC) pain relief medication. Options include acetaminophen (Tylenol), aspirin, or ibuprofen (Motrin, Aleve).

If these treatments do not resolve symptoms, injections are available to help achieve the desired effects.

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

In the past, some doctors have also suggested injections of hyaluronic acid, but current guidelines do not recommend these. This is because there is not enough evidence to show that they are safe and effective.

In this article, we provide an in-depth examination of both types of injection, their uses, and their possible side effects.

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.

The Food and Drug Administration (FDA) have approved five different steroid medicines to treat OA. All of them are about equally effective.

The FDA have also recently approved an extended release corticosteroid injection of triamcinolone acetonide (Zilretta). A person can have it only once, but its anti-inflammatory effects may last longer.

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. Ultrasound is a scan that uses sound waves to create images of the inside of the body.

The doctor may also give an injection of anesthetic pain relief alongside the injection, which will provide immediate relief. The steroid should start taking effect within a few days.

However, 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.

People with a extensive damage in the knee are less likely to see results. Even if the pain does improve, it may start to return from a few weeks to a few months after the shot.

Side effects

Although the FDA considers corticosteroid shots to be safe, people might experience side effects, such as:

  • crystal flares, or irritation in the joint similar to gout
  • nerve damage
  • in rare cases, infection
  • an increase in blood sugar levels, a side effect particularly common in people with diabetes
  • thinning of the bones near the knee

If the effects wear off, people receiving the injection 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. The pain relief from the injection will also not be as effective and wear off more quickly.

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

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Speak to a doctor about whether knee injections will help your presentation of OA.

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

Two other types of injections are available. Although these treatments are still experimental and not yet FDA-approved for arthritis of the knee, some doctors may be able to use them.

Platelet-rich plasma (PRP) injections

These injections use cells called platelets. These help wounds heal and blood clot. The doctor takes the platelets from the individual’s own blood. Once inside the knee joint, platelets release growth factors, which are substances that help fix damaged tissues.

PRP injections may relieve OA pain and improve function, although researchers must provide further evidence before this treatment enters the mainstream.

Other injections that people have used include platelet-rich plasma (PRP) and stem cell injections.

Current guidelines advise against using this kind of treatment for OA of the knee, as there are no standards regulating its use. This means that a person cannot be sure what is in the injection.

Corticosteroids injections can treat OA in the knee.

However, the effects are not permanent. As they wear off, a top-up will likely be necessary. However, a person should not receive steroid injections more than once in a 3–4 month period as this increases the risk of side effects.

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

Speak to a doctor to assess whether knee injections are right for you.