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A therapeutic joint injection is designed to provide relief from pain and other symptoms associated with a diseased joint via the administration of medication to the affected joint1. Arthrocentesis is just the opposite; it involves aspirating, or sucking out, fluid from a joint for diagnostic purposes and to alleviate swelling. Both procedures involve the insertion of a needle into a joint capsule for medical benefit, but differ only in the direction of fluid flow.
Today, most injections consist of an anesthetic (pain reliever), a corticosteroid (anti-inflammatory), or a combination of the two(2, 4). Joint injections are a valuable technique for the detection and treatment of joint disease, particularly for arthritis, or inflammation of joint (synovial) tissue. Injections may be performed in a variety of different joints, including the(2, 3):
The knee is one of the most common sites of injection, typically for the treatment of arthritis. Arthrocentesis of the knee is also commonly performed to investigate potential infection of the joint and relieve pain due to swelling.
Arthrocentesis is also performed to assess for infection following hip surgery. Sacroiliac joint injections where the spine meets the pelvis have been used to relieve lower back and leg pain.
Injection of the shoulder is done primarily for contrast diagnostic imaging with MRI, but may also be done for adhesive capsulitis, in which the glenohumeral (GH) joint becomes inflamed and stiff. Injections may also be done at the acromioclavicular (AC) joint for age-related degeneration.
Injection of the wrist is often performed in a diagnostic capacity to distend the joint and detect fibro-cartilaginous tears in associated soft tissue.
Injection of the elbow joint is often done to distend the joint with fluid to aid in the diagnosis of bone abnormalities, but can also be used in the treatment of lateral or medial epicondylitis, also known as tennis or golf elbow respectively.
Injections of joints in the finger, ankle and spine are also common(2, 3). Over several decades, a variety of diagnostic and therapeutic indications have developed for joint injections; each will be discussed separately(3).
Arthrocentesis can be used to acquire fluid from a diseased joint for definitive analysis of a disease process1. The procedure is performed in joints where swelling or effusion is obvious, and can be used to provide important information regarding the disease process when diagnosis is uncertain.
Arthrocentesis is commonly used to:
- Characterize arthritis as septic (infectious), inflammatory or non-inflammatory
- Diagnose gout by looking for characteristic uric acid crystallization
- In the case of septic arthritis, diagnose the microbial agent responsible for properly tailored antibiotic therapy
In many cases joint injections can also serve a diagnostic purpose; they can also be used to confirm diagnosis of a disease state4. Injections of anesthetic can be used to identify potential sources of pain; if anesthetic injection into a suspected site relieves pain, it provides confirmation that the site may be the source of pain(3, 4). Injections of contrast material can make it easier to distinguish between normal and abnormal tissue on radiologic examination with x-ray, CT, MRI and other modalities.
Commonly used diagnostic injections include:
- Cervical, thoracic and lumbar epidural cortisone injections for spinal pain
- Cervical and lumbar zygapophyseal, or facet joint injections for neck and low back pain
- Sacroiliac joint injections for low back pain
- Lumbar, thoracic and cervical discography injections for inter-vertebral disc pain
In many cases a diagnostic injection can simultaneously provide temporary pain relief, helping to bridge the gap between diagnosis and treatment.
Joint injections may be combined with arthrocentesis to achieve symptomatic relief for patients suffering from painful, swollen joints1. For non-inflammatory disease processes, arthrocentesis alone may be enough to provide pain relief. For inflammatory joint disease, removal of fluid ahead of time via arthrocentesis has been shown to increase the effectiveness of anti-inflammatory steroid injections1. Therapeutic injection of steroids may be beneficial for the treatment of joints affected by inflammatory arthritis, as corticosteroids are an anti-inflammatory medication.
Therapeutic joint injections are commonly used for the following conditions:
Rheumatoid arthritis (RA)
RA is life-long disease that causes inflammation in joints throughout the body, particularly in the wrists, fingers and knees. RA is an autoimmune disease, in which the body’s immune system targets its own tissue (in this case synovial tissue) for destruction. Steroid joint injections are nearly always effective for pain management in affected joints when combined with other medical therapies1. In one study, injected joints of 75% of patients remained in remission at seven years1. Injections may also be helpful in a childhood form of this disease, known as juvenile rheumatoid arthritis.
Crystal-induced arthritis (Gout)
Gout refers to an arthritis that occurs due to the buildup of uric acid in the blood, which can solidify as crystals in the joint and cause inflammation. Corticosteroid injections may be helpful in relieving painful symptoms within 24 hours(1). One recent report showed short-term effectiveness in relieving pain and swelling for 100% of study participants.
Osteoarthritis is one of the most common joint disorders, which is caused by age- and trauma-related degeneration of a joint. Joint injections may be of small benefit in the short-term treatment of OA, with one study reporting 60-80% pain improvement for up to six weeks; after six weeks, however, the pain levels returned to baseline1.
Back and neck pain
Back and neck pain can be caused by degeneration of facet joints in the spine, or the compression of nerves which supply the joints. The joints connect together the vertebrae which comprise the spinal column. Injections of the facet joints of the spine have shown benefit for the treatment of low back and neck pain in some cases.
Therapeutic joint injections have also been shown to be effective in the management of inflammatory joint disease in the spinal column (spondyloarthropathies) and the sacroiliac joint1, 2.
Prior to injection, the patient is educated about what will happen during the procedure, any possible complications, and proper care for the joint after the procedure is completed(2).
For injections in general, a patient is positioned on a procedure table in such a manner as to provide for patient comfort while simultaneously granting appropriate access to an injection site(4). For a given joint injection, there may be a variety of approaches available; the approach is typically chosen at the physician’s discretion in the best interests of the patient. Site selection is based on ease of access to the joint capsule as well as avoidance of neurovascular tissue(2). The patient is then draped for modesty and the injection site is sterilized to prevent infection once the skin is perforated. In some cases, topical anesthetic or small local injections of anesthetic can be applied around the joint injection site to numb the area and prevent discomfort for the patient1.
A needle is then guided into the joint capsule for the purposes of medication administration (injection), or synovial fluid removal (arthrocentesis) (3). In some cases needle placement is performed without radiologic guidance, based on a physicians experience and knowledge of anatomy. In other cases, radiologic guidance can be used to assist with accurate needle placement. The gold standard for radiologic guidance for joint injections is a technique called fluoroscopy, in which x-ray images are generated in real-time, so that a physician can visualize motion of the needle through soft tissues and into the joint as if it were on camera(1, 4).
Joint injections and arthrocentesis are relative safe and simple procedures that can usually be performed at an outpatient clinic or procedural center(1). Patients are generally informed of complications that may occur following injection, and are instructed to seek medical care for sudden onset of fever, redness, swelling or severe pain in the joint. Following a joint injection or arthrocentesis procedure, activity and use of the joint should be restricted, particularly for weight-bearing joints1.
Potential complications of arthrocentesis and joint injections include:
- Painful ‘flare-up’ immediately after injection
- Changes in skin color or sensation
- Soft tissue weakening and bone degeneration
- Systemic steroid absorption from inadvertent steroid injection into blood vessels, which can cause:
- Flushing, warmth and sweating
- Temporary increase in blood sugar and blood pressure
- Temporary immunosuppression
Most complications associated with joint injections consist of local irritation of the injection site and joint tissues, followed by temporary pain ‘flare-ups’ reported by anywhere from 1-6% of patients(1). Infection is perhaps the most serious, yet least common complication of arthrocentesis and joint injections, with reports of incidence ranging from 0.001 – 0.005%.
Complications as a result of joint injections tend to be rare, and when they do occur, they tend to be mild(4).
Future Directions for Joint Injections
The use of ultrasound guidance for joint injections and arthrocentesis has received considerable attention in recent years5. An ultrasound machine can be used prior to insertion of a needle to determine the exact location and distance to the joint, or can be used concurrently with needle insertion to assist in guidance to the joint. Providing real-time feedback of the needle location whilst in soft tissue has been hypothesized to increase the accuracy of needle placement, and thus increase the efficacy of arthrocentesis and joint injections. A comparative study showed ultrasound guidance dramatically increased the ability to obtain joint fluid via needle aspiration, and improved response to joint injections in shoulders, fingers and ankles(5).
With increased understanding of the biology of joints and improved techniques for accessing joints, coupled with novel pharmaceutical agents have opened the door to future joint therapies with the potential to go beyond injections of anesthetic and steroids for the relief of pain and inflammation. Emerging joint therapies consist of medications able to target specific molecular processes of inflammation and bone destruction in joints and promote cartilage growth, and an ability to transfer genetic material and synovial cells to joint tissue5.
Joint injections are a valuable technique for the detection and treatment of joint pathology, which have been improved with advances in imaging technology that have increased needle placement accuracy(3). Joint injections represent a burgeoning area of research in terms of improved diagnostic capability, improved treatment regimens via targeted pharmaceutical therapy, and improved outcomes as imaging technology evolves and is applied to injections and arthrocentesis.
- Joint Injections – PainDoctor.com
- Wise, C. (2008). Arthrocentesis and Injection of Joints and Soft Tissue. Firestein: Kelley’s Textbook of Rheumatology, 8th Ed. MD Consult Web site, Core Collection.
- Roberts, W.N. (2011). Joint aspiration or injection in adults: technique and indications. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2010.
- Malfair, D. (2008). Therapeutic and Diagnostic Joint Injections. Rad Clin N Am. Vol. 46(3), 439-453.
- Williams, K.; Park, A. (2007). Injection Studies. Canale & Beaty: Campbell’s Operative Orthopaedics, 11th Ed. MD Consult Web site, Core Collection.
- Wise, C. (2008). Current and Future Trends in Arthrocentesis and Joint Injection. Firestein: Kelley’s Textbook of Rheumatology, 8th Ed. MD Consult Web site, Core Collection.