The term “intraarticular” describes the space within a joint. This space, enclosed by a fibrous joint capsule, contains synovial fluid, which lubricates the joint to allow for smooth movement. In medicine, the term is most frequently used to describe delivering medication directly into the joint space through an injection.
Purpose of Intraarticular Treatments
The primary goal of an intraarticular treatment is to deliver a therapeutic substance directly to the source of a joint issue. This localized approach allows for a high concentration of the medication at the site of pain and inflammation, which can enhance its effectiveness. By containing the treatment within the joint, exposure to the rest of the body is minimized, reducing the likelihood of systemic side effects.
One objective is to reduce inflammation and swelling inside a joint. This leads to pain relief for the patient. Another purpose is to supplement the natural fluid in the joint, which can improve lubrication and shock absorption, thereby enhancing mobility. Beyond therapy, these injections can serve a diagnostic purpose. Injecting a local anesthetic and observing temporary pain relief can help a physician confirm that a specific joint is the origin of the discomfort.
Commonly Injected Substances
Corticosteroids are powerful anti-inflammatory drugs. Medications like triamcinolone and methylprednisolone work by interrupting inflammatory pathways at a cellular level, which can downregulate the immune response that causes pain and swelling in conditions like osteoarthritis and rheumatoid arthritis. The effects of these injections can reduce stiffness and improve function for weeks or months.
Viscosupplementation involves injecting hyaluronic acid (HA). HA is a polysaccharide that occurs naturally as a major component of healthy synovial fluid and cartilage, giving the fluid its viscous, lubricating properties. In joints affected by conditions like osteoarthritis, the concentration and molecular weight of HA can decrease. Supplementing it aims to restore the fluid’s ability to lubricate the joint and absorb shock, which may also have a secondary anti-inflammatory effect.
Local anesthetics such as lidocaine or bupivacaine are often included in intraarticular injections, frequently mixed with a corticosteroid. The primary function of the anesthetic is to provide immediate, though short-term, pain relief. This rapid effect can be comforting for the patient. The relief from the anesthetic typically lasts for a few hours.
Newer biologic treatments are also utilized, such as Platelet-Rich Plasma (PRP). This therapy uses the patient’s own blood, which is drawn and placed in a centrifuge to separate and concentrate the platelets. This platelet-rich concentrate is then injected back into the joint. The underlying theory is that platelets release numerous growth factors that can help modulate the joint environment, reduce inflammation, and potentially stimulate the body’s natural healing and repair processes.
The Injection Procedure
The patient is positioned to allow the clinician clear access to the targeted joint. The skin over the injection site is cleaned with an antiseptic solution, such as chlorhexidine or iodine, to minimize the risk of infection. To reduce discomfort at the injection site, a topical anesthetic spray or a small injection of a local numbing agent may be applied to the skin.
A needle is carefully inserted through the skin and guided into the intraarticular space. To ensure the needle reaches the precise location within the joint, clinicians often use imaging guidance. Fluoroscopy, a type of live X-ray, or ultrasound are commonly employed to visualize the needle’s path. This visualization helps avoid sensitive structures like cartilage and blood vessels, increasing the accuracy and safety of the procedure.
Patients are advised to rest the joint for 24 to 48 hours and to apply ice to the area to help manage any potential swelling or discomfort. While complications are rare, patients are instructed to monitor the site for signs of infection, such as increasing redness, warmth, or the onset of a fever. Some individuals may experience a temporary “post-injection flare,” where pain and inflammation in the joint briefly increase before subsiding.