The joint is usually injected from the extensor surface at a point where the synovium is closest to the skin. This site minimizes the interference from major arteries, veins, and nerves. When the point of injection has been determined, it is best marked with the tip of a retracted ballpoint pen or a needle hub by pressing the skin to produce a temporary indentation to mark the point of entry. The skin is then prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. The skin and subcutaneous tissue at the injection site may be anesthetized by injecting 1% lidocaine, with no epinephrine, using a 25- to 30-gauge needle. Alternatively, 5% lidocaine-prilocaine cream may be applied to the skin surface for 15 to 30 minutes prior to skin preparation or a vapocoolant spray may be applied to the skin surface after skin preparation to provide adequate anesthesia (53,54).
A 1½- to 2-in. (4- to 5-cm), 22- to 25-gauge needle is then pushed gently into the joint. Before injecting the medication, an attempt should always be made to aspirate to avoid accidental intravascular injection. After ensuring that the needle is in the joint space, the medication should be injected in a slow, steady fashion.
Ultrasound guidance has been reported in multiple studies to increase accuracy for needle placement for arthrocentesis and therapeutic steroid injection in joints and tendon sheaths (55–58). One study demonstrated that needle guidance with ultrasound increased the ability to obtain synovial fluid from joints to 97% of patients compared with 32% when using conventional techniques without ultrasound (58).
Indications for Intraarticular Injection
Intraarticular injections may be used to determine the source of pain as articular or extra-articular and to provide maximal control of inflammation in joints when nonsteroidal antiinflammatory drug (NSAID) therapy has failed or is contraindicated. Intraarticular injections are indicated to decrease morbidity in self-limited, sterile, inflammatory conditions. Intraarticular injections provide rapid relief of inflammatory pain and facilitate physical therapy of an inflamed joint. Poorly controlled inflammation in more than three joints requires reconsideration of systemic corticosteroids.
The intraarticular injection of hyaluronate for osteoarthritis is a relatively new technique. The viscosupplement acts like synovial fluid to maintain lubrication of the joint. This may be used in early osteoarthritis but does not appear to be an efficacious treatment in advanced osteoarthritis (59).
Contraindications for Intraarticular Injection
Contraindications must be considered before the injection of any joint. Contraindications to intraarticular injection include overlying soft-tissue sepsis, bacteremia, anatomic inaccessibility, an uncooperative patient, articular instability, septic arthritis, avascular necrosis, osteonecrosis, and neurotrophic joints.
Steroid injection into Charcot’s joint is contraindicated because local steroids will not provide significant long-term relief of the symptoms. Avascular necrosis in Charcot’s joints has been correlated to corticosteroid injections. Another specific contraindication is injection of an unstable joint unless the instability is appropriately corrected by bracing or surgery. Traumatic arthritis, secondary to fracture through the joint, is another contraindication for steroid injection because the beneficial effects of the steroid injections are not long lasting. Severe osteoporosis in areas around the joint is also a contraindication for injecting steroids.
Injection of joints with surgical implants is relatively contraindicated because these joints are more prone to infection than intact joints and are usually inflamed secondary to infection rather than synovitis. Injection of corticosteroids into a nondiarthrodial joint is rarely of value because there is no synovial sac in which to decrease inflammation.
The amount and type of corticosteroid vary extensively in the musculoskeletal application. The type of corticosteroid chosen is often based on purpose, expected duration, availability, and preference of the practitioner. Suggested guidelines for maximum amounts with intra articular injections include (60)
- Large joints (e.g., hip)—80 mg triamcinolone acetonide or equivalent
- Medium joints (e.g., knee)—40 mg triamcinolone acetonide or equivalent
- Small joints (e.g., wrist)—20 mg triamcinolone acetonide or equivalent
- Very small joints (e.g., metacarpal phalangeal, zygapophyseal facet)—5 to 10 mg triamcinolone acetonide or equivalent Suggested guidelines for maximum amounts with bursa injections include
- Large bursa (e.g., subacromial)—20 mg triamcinolone acetonide or equivalent
- Medium bursa (e.g., olecranon)—10 mg triamcinolone acetonide or equivalent
- Small bursa (e.g., anserine, retrocalcaneal)—1 to 5 mg triamcinolone acetonide or equivalent
The few complications associated with corticosteroid injections include infection, postinjection inflammation, and tissue atrophy. The occurrence of joint infection is extremely rare with the use of appropriate sterile techniques. Hollander described an incidence of 0.005% in more than 400,000 consecutive injections (10). There is a paucity of research regarding the efficacy and duration of action of various corticosteroids in joint and soft-tissue injections. The use of less soluble corticosteroids (acetate suspensions, e.g., methylprednisolone diacetate, triamcinolone acetonide) results in the steroid remaining in the joint and an assumed longer action. This decreased solubility results in increased possibility of postinjection flare. The use of more soluble corticosteroids (phosphate solutions, e.g., prednisolone sodium phosphate) results in more rapid absorption and an assumed shorter action. This increased solubility results in increased possibility of soft-tissue atrophy (61). Postinjection inflammation is often secondary to corticosteroid crystal–induced synovitis and may mimic iatrogenic infection. This normally lasts 4 to 12 hours and is treated with NSAIDs and local application of ice. If this persists beyond 24 hours, the patient should be reevaluated to rule out infection. Postinjection flares may last up to 48 hours. The incidence of postinjection inflammation has been estimated at 1% to 6%. Repeated intraligamentous injections may result in calcification and rupture of the ligaments. Penetration of the articular cartilage will result in damage. Traumatic injection is prevented by never injecting against resistance.
Multiple studies on the weight-bearing joints of humans and primates treated with frequent corticosteroid injections have produced conflicting results regarding the adverse effects of corticosteroids on articular cartilage (17,61). However, due to the continued controversy regarding negative effects of corticosteroid injections on cartilage, it is recommended that intraarticular injections should be performed with intervals of at least 3 months to minimize complications to the cartilage or supporting ligaments.
Tissue atrophy in the area of injection occurs when corticosteroid is placed outside the joint space or leaks from the joint space. If a portion of the injected intraarticular corticosteroid is absorbed into the systemic circulation, the result may be an elevation of blood sugar, hormonal suppression, and brief, generalized improvement in all inflamed joints. Corticosteroid injections are not recommended immediately after an acute injury or immediately before an athletic event. A patient should have a period of joint immobilization, rest, and protection from further injury after injection (62).
Before the injection, the appropriate landmarks are located and marked. The skin is scrubbed with antiseptic and allowed to dry for 2 minutes. The wearing of sterile gloves is required so that the bony landmarks in the sterile field may be palpated throughout the procedure. Standard sterile technique is required to minimize risk for a septic joint. It is preferable to use single-dose vials of the steroid preparation and local anesthetic agent because this further reduces the risk for infection. A 25- to 27-gauge needle is used with 1% lidocaine, and no epinephrine, to raise a small skin wheal for skin anesthesia. Routinely, a 1½-in. (4-cm), 21- to 25-gauge needle traverses the skin, joint capsule, and synovial lining, sliding smoothly into the joint cavity. One must avoid the periosteum of the bone as well as the articular cartilage during this procedure. Aspiration is done to ensure there is no intravascular penetration. The return of synovial fluid ensures the position of the needle in the joint space; however, often there is minimal to no aspirated fluid. If there is an effusion, the fluid is removed in a slow, steady fashion until all possible joint fluid is aspirated. If the fluid is yellow and clear, the likelihood of infection is minimal, and the corticosteroid may be injected. If the fluid appears turbid, it should be sent for synovial analysis, including culture and sensitivity testing for microorganisms. If infection is suspected, the steroid injection into the joint should be postponed until the culture and sensitivity reports are completed. In addition to examining the color of the fluid, the viscosity of the fluid may be determined by putting a couple of drops of the fluid between the gloved thumb and index finger and stretching it. Normal synovial fluid has a good viscosity and is usually able to stretch for 2 to 2.5 cm. However, if there is an inflammatory process occurring in the joint, the viscosity of the fluid will be significantly decreased with a hazy or cloudy presentation (Table 67-6). The synovial fluid analysis completed in the laboratory may include rheumatoid factor, albumin, complements, protein electrophoresis, glucose level, and cell count with differential. A high white-cell count may indicate an inflammatory process. The fluid for culture and sensitivity should be sent immediately to the laboratory because infections caused by fastidious gonococcal organisms do not survive long in the test tube. Corticosteroids should not be injected into a joint until infection, including that caused by mycobacteria or fungi, has been excluded.
Aspiration from the joint may be impeded by synovial tissue over the end of the needle, intraarticular debris, and excessive joint fluid viscosity. It also may be difficult to aspirate if the tip of the needle is against or imbedded in the articular cartilage or if the needle is not in the joint cavity. It is important to ensure that the entire needle is withdrawn intact, because there have been reports of the separation of the needle from the hub and of needle fracture in articular injections.
The ease with which medication can be injected into the joint provides an indication as to the appropriate placement of the needle. No resistance should be encountered during the injection. If this occurs, the needle should be repositioned and aspirated to ensure that blood vessels have been avoided, and then the medication should be slowly injected. After the medication has been injected, the needle should be cleared with a new syringe containing a small amount of lidocaine or saline. The needle is then withdrawn with pressure applied to minimize bleeding. Joint injections are used primarily to deliver corticosteroids and anesthetic agents to treat inflamed synovium, bursa, and tendon.
Long-acting steroid preparations may induce a crystal synovitis 24 hours after the injection that resolves spontaneously. The patient should be cautioned about possible short-term aggravation of symptoms in the affected joint. It is recommended to infiltrate the subcutaneous tissues and the joint capsule with 2 to 4 mL of 1% lidocaine without epinephrine. When long-acting anesthetic agents are injected into the joint, it is important to advise the patient to limit usage of that joint during the first 24 hours after injection to prevent injury.