Intra-Articular Injections to Treat Joint Disorders

Benefits, Risks, and Limitations of Joint Injections

knee injection
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An intra-articular injection is a term used to describe a shot delivered directly into a joint with the primary aim of relieving pain. Corticosteroids (steroids) were the first substances used for this purpose. Other types of drug are now commonly used including local anesthetics, hyaluronic acid, and even Botox.

An intra-articular injection is typically given when a pain has not responded to more conservative treatments including pain relievers, oral anti-inflammatory drugs, and physical therapy.

Types of Intra-Articular Injections

The aim of intra-articular injections can vary by the drug used. While pain relief is the most common goal, they may also be used to deliver chemotherapy drugs like Doxil (doxorubicin) directly into a joint affected by cancer. They may also be an effective means of eradicating a fungal infection in joints (also known as fungal arthritis).

When used for pain alleviation, different intra-articular therapies work in different ways:

  • Corticosteroids work by decreasing local inflammation. They do so by inhibiting the production of inflammatory cells that are naturally produced in response to an acute injury or chronic condition. Intra-articular treatments are most commonly used to treat osteoarthritis, acute gout, and rheumatoid arthritis of the knee. However, long-term use of corticosteroid use is known to progressively damage to joints.
  • Hyaluronic acid is a naturally occurring substance found in synovial fluids that lubricate the joints. With osteoarthritis, this substance can rapidly break down and lead to a worsening of the condition. Intra-articular injections aim to increase lubrication, reduce pain, and improve the range of motion in a joint. Clinical studies have been mixed on how effective these shots really are.
  • Local anesthetics are sometimes delivered by intra-articular injections as a form of pain relief following arthroscopic surgery. But it is a practice that has come under scrutiny as evidence suggests that it may degrade chondrocytes (the only cells found in cartilage) in the joint.
  • Botox (botulinum neurotoxin A) injections have been shown to provide significant pain relief to people with advanced knee osteoarthritis. However, the on-going use of Botox does not appear to improve or restore the physical function of the joint.
  • Platelet-rich plasma (PRP) is derived from whole blood and contains platelets (red blood cells central to clotting) and the liquid portion of blood known as plasma. Intra-articular injections of PRP have been shown to reduce pain and improve physical function in persons with osteoarthritis while supporting the regeneration of collagen in joints. Some people benefit more than others, however, and most do not improve per se but rather experience a slowing in the progression of arthritis.

Treatment Considerations

The two main side effects associated with intra-articular injections are infection and local site reactions. Other side effects can occur in relation to the specific drugs or substances injected.

Intra-articular injections, by and large, should never be considered the sole means of treatment of osteoarthritis or other joint disorders. The effects of many of these drugs tend to wane over time, and the negative impact on the joints themselves can sometimes be profound.

When used, corticosteroid shots should given no less than three months apart. The duration of relief can vary based on the type of steroid used:

  • Hydrocortisone is typically weak and short-acting.
  • Methylprednisolone preparations can work for one to two weeks.
  • Celestone (betamethasone) can work for two to eight weeks.
  • Kenalog and Aristocort (preparations of triamcinolone) can work for four to 16 weeks.
  • Aristopan (another triamcinolone preparation) can last for months.

Hyaluronic acid injections, by comparison, are typically administered as a series of shots scheduled over three to five weeks. They are mainly used to buy time before a knee replacement surgery in people who are unable to tolerate steroids and have not found relief from oral medications.

Botox, meanwhile, appears to cause less damage to cartilage, has few side effects, and appears effective in treating severe cases of osteoarthritis.

With that being said, there is no clear consensus on appropriate use. Treatment effects can last as long as 12 weeks in some people and as short as four weeks in others.

PRP has no known side effects, but its effectiveness can vary significantly from person to person. Treatment benefits can last anywhere from six to nine months.

Sources:

Evans, C.; Krause, V.; and Setton, L. "Progress in intra-articular therapy." Nat Rev Rheumatol. 2014; 10(1):11-22.

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