Injections have been an important adjunct for the management of musculoskeletal disease for more than 50 years. As with any procedure, success depends on knowing the right diagnosis (who to inject), performing the correct procedure (how to inject), and using the most appropriate pharmacologic agent (what to inject).
|Clinical recommendation||Evidence rating||References|
|Corticosteroid injection without splinting is the preferred initial treatment for de Quervain tenosynovitis.||B||1, 2|
|Corticosteroid injection for trochanteric pain is safe and highly effective. With trochanteric pain, satisfactory pain relief often is achieved with a single corticosteroid injection.||C||4, 5|
|Subacromial corticosteroid injection provides short-term pain relief that is greater than placebo and at least equal to nonsteroidal anti-inflammatory drug therapy.||B||9, 11, 12|
|Corticosteroid injection reduces short-term (less than six weeks) symptoms from lateral epicondylitis, but physical therapy is superior to steroid injection after six weeks.||A||13, 15, 16|
|Intra-articular steroid injections reduce pain and swelling in osteoarthritis of the knee.||A||17|
|The addition of local anesthetics to steroid injections improves pain relief and can be used to differentiate local from referred pain.||C||30, 46, 47|
Who to Inject?
The most common indications for therapeutic injections are presented in Table 1. In general, injections can be within the joint space (intra-articular), around the joint space (periarticular), or within specific soft tissue structures. Injections can be used to definitively treat a condition, to provide a pain-free window for rehabilitative therapy (which is ultimately curative), or to provide episodic pain and symptom relief.
|Adult and juvenile rheumatoid arthritis|
|Crystal-induced arthritis (gout; pseudogout)|
|Spondyloarthropathies (Reiter syndrome; psoriatic arthritis)|
|Osteoarthritis (most commonly of knee, distal interphalangeal, proximal interphalangeal, carpometacarpal and metatarsophalangeal joints)|
|Carpal tunnel syndrome|
Injections for Definitive Treatment
DE QUERVAIN TENOSYNOVITIS
Corticosteroid injections are curative for de Quervain tenosynovitis, a common overuse tendon injury of the hand and wrist. Steroid injections provide the highest cure rate compared with nonsteroidal anti-inflammatory drug (NSAID) therapy, splinting, or combination therapy.1,2 A pooled analysis of seven observational studies found that steroid injection alone was curative in 83 percent of cases compared with splinting alone (14 percent), rest (0 percent), or NSAID therapy (0 percent).2 Most patients are symptom free after a single injection, and injection for the treatment of de Quervain tenosynovitis is safe during pregnancy, postpartum (when the incidence increases), and while breastfeeding.3
Trochanteric bursitis is the second leading cause of hip pain in adults. Trochanteric steroid injection is simple, safe, diagnostic, and usually therapeutic.4 Patients treated with a steroid-anesthetic injection report rapid and prolonged improvement of pain and disability,5 often after a single injection. A retrospective cohort study comparing treatments for trochanteric bursitis showed a 2.7-fold increase in the number of patients who were pain free five years after a single corticosteroid injection compared with those who did not receive an injection.6
Because it is safe, simple, and effective, physicians should offer steroid injection as first-line treatment for trochanteric bursitis, particularly in older adults. Physical therapy modalities and NSAIDs are second-line agents for pain relief in patients with trochanteric bursitis. Therapeutic strengthening and stretching exercises are helpful for younger or more athletic patients and for those with recurrent symptoms.
INJECTION FOR PAIN CONTROL DURING REHABILITATION
Definitive treatment of subacromial pain (rotator cuff syndrome) always involves physical therapy to strengthen the rotator cuff. Shoulder pain prevents many patients from adequately performing rehabilitative exercises, carrying out activities of daily living, and obtaining uninterrupted sleep. Therefore, a common clinical dilemma is how to best control pain to allow for adequate rehabilitative physical therapy. Systematic reviews of treatments for subacromial pain, subacromial impingement, and rotator cuff syndrome favor corticosteroid injection over the following options: ergonomic changes, nonsteroidal drug therapy, acupuncture, range of motion and strengthening exercises, ultrasound, ice, heat, and physical therapy.11,12 Subacromial injection is particularly helpful in differentiating between shoulder weakness caused by impingement (shoulder strength improves after injection) and a true rotator cuff tear (no change in strength is noted following injection).
Lateral epicondylitis (i.e., tennis elbow) is a common cause of elbow pain. Corticosteroid injection yields a predictable short-term (less than six weeks) decrease in pain13,14 that is superior to nonsteroidal drug therapy15 and physical therapy.16 After six weeks, however, physical therapy reduces symptoms more than corticosteroid injection.16 Therefore, corticosteroid injection should be reserved for patients whose symptoms limit participation in physical therapy or activities of daily living.
Injection for Pain Relief: Arthritis
The most common indication for intra-articular injection is arthritis. For short-term treatment of osteoarthritis of the knee, intra-articular steroid injection improves function and reduces swelling and pain.17 The onset of action is rapid (typically within 24 hours) and clinical effects last four to eight weeks. Repeated steroid injections for osteoarthritis of the knee are safe and do not accelerate disease progression.18 Although steroid injections are effective for osteoarthritis of the hip,19 technical challenges with this procedure preclude its routine use. Intra-articular corticosteroids are less effective for treating osteoarthritis of the thumb20 and shoulder.11
Injection for Symptom Relief: Carpal Tunnel Syndrome
Carpal tunnel syndrome affects nearly 4 percent of the general population. Local corticosteroid injections provide greater symptom relief for one month after injection compared with placebo (number needed to treat [NNT] = 2) and oral corticosteroids. However, significant symptom relief after one month has not been demonstrated following injection.21 Also, as many as one third of patients will improve spontaneously. Prospective data suggest that for patients who fail initial therapy with bracing or oral anti-inflammatory medications, clinical outcomes at one year are similar in patients treated with corticosteroid injections versus surgery.22
How Often to Inject?
Data from studies of patients with rheumatoid arthritis23 suggest it is safe to perform multiple steroid injections on the same joint. The recommended interval between intra-articular injections is three months.24 Injection frequency should be guided by the underlying disease process, the response to past injections, the availability of other treatment options, patient preferences, and clinical judgment.
What about Diabetes?
A clinical concern is the effect of steroid injection on blood glucose levels in patients with underlying diabetes. Single intra-articular steroid injections have little or no effect on glycemic control.25 However, injection of soft tissues or peritendinous injections can cause elevations in blood glucose26,27 that persist from five to 21 days. Patients with diabetes who undergo soft tissue injections require closer glycemic monitoring and follow-up in the weeks following the procedure.
How to Inject?
A series of articles reviewing the technical aspects of joint and soft-tissue–specific injections has been published in American Family Physician.28–30 Contraindications to intra-articular injection are presented in Table 2. If the underlying diagnosis is unknown, aspiration and synovial fluid analysis should be performed for diagnostic purposes. Although ultrasound imaging can be used to direct or confirm injection location,31 the use of standard anatomic landmarks results in correct needle placement in most uncomplicated cases.32
|Broken skin at injection site|
|Known hypersensitivity to intra-articular agent|
|Severe joint destruction|
|Skin infection overlying injection site|
Informed consent should always be obtained before performing the procedure. Injections should be performed using aseptic technique. A 1.5 inch, 21-gauge needle is typically used to inject larger joints such as the knee or shoulder. Smaller (0.5 inch) 23- or 25-gauge needles suffice for smaller joints. The viscosity of some steroid preparations precludes injection through smaller-bore needles. To perform aspiration and injection consecutively, physicians can either use a reciprocating device33 or the joint injection technique described in Table 3.
|Steps for combined intra-articular aspiration and injection|
|1. Determine indication for procedure.|
|2. Obtain informed consent; discuss risks, benefits, and alternatives with the patient.|
|3. Prepare equipment, including laboratory requests, needles, syringes, and medication.|
|4. Identify and mark the appropriate anatomic landmarks to guide needle placement.|
|5. Clean overlying skin using isopropyl alcohol (povidone iodine [Betadine] also can be used).|
|6. Use cooling spray or local anesthetic for patient comfort (as needed).|
|7. Select appropriate length and gauge of needle; judiciously guide needle into intra-articular space.|
|8. Gently aspirate fluid (procedure should not be painful).|
|9. Anchor needle with hemostat to prevent migration from the intra-articular space.|
|10. Remove aspirant syringe and replace with syringe Containing steroid and/or anesthetic for injection.|
|11. Inject medication into the intra-articular space (fluid should move freely into the joint space); if resistance is met, try rotating or repositioning syringe to ensure that the needle is still in the correct space.|
|12. Remove needle and apply bandage.|
|13. Provide post-procedural counseling.|
The most common complications of intra-articular injection are a postinjection flare of pain (2 to 10 percent), skin atrophy (1 percent), fat atrophy (1 percent), and facial flushing (less than 1 to 12 percent) (Table 4).34–36 Less commonly reported side effects include iatrogenic infection (risk of 1 in 1,000) and tendon rupture (less than 1 percent). The risk of tendon rupture is highest with soft tissue injections around the Achilles tendon and plantar fascia.37
|Post-injection flare||2 to 10|
|Joint infection||< 0.001 to 0.072|
|Surrounding tissue effects|
|Tendon rupture||< 1|
|Skin atrophy/depigmentation||< 1|
|Vasovagal reaction||10 to 20|
|Facial flushing||< 1|
|Hypersensitivity reaction||< 1|
What to Inject?
There is little systematic evidence to guide corticosteroid selection for therapeutic injections. Most recommendations are based on a combination of clinical experience and personal preference. However, knowledge about the mechanism of action of individual steroids can guide steroid selection in various situations.
The clinical effects of steroids result from several different mechanisms of action. Intra-articular corticosteroids reduce synovial blood flow,38 lower the local leukocyte and inflammatory modulator response,39 and alter local collagen synthesis.40 These effects combine to reduce pain and inflammation. Hydrocortisone esters are more effective in producing these effects than their parent compounds. Branched esterification further reduces solubility, allowing steroids to remain at the injection site longer.38 Clinically, insoluble steroids have a longer duration of action and a higher incidence of cutaneous side effects. Triamcinolone hexacetonide (Aristospan) is the least soluble of the commonly used injectable steroids, followed by triamcinolone acetonide (Kenalog).
In the United States, methylprednisolone acetate (Depo-Medrol) is the most commonly used intra-articular steroid, followed by triamcinolone hexacetonide and triamcinolone acetonide.41 Many physicians empirically use triamcinolone hexacetonide (low solubility, longer duration of action) for intra-articular injection, and betamethasone (high solubility, shorter duration of action, fewer cutaneous side effects) for soft tissue injections.
Early trials of intra-articular corticosteroids showed equal systemic absorption of methylprednisolone in patients with rheumatic and osteoarthritic hands42 and knees.43 This suggests that steroid pharmacokinetics, rather than disease-related factors, should guide steroid selection. A recent review by the National Health Service of the United Kingdom44 recommends triamcino-lone and methylprednisolone as preferred agents for injection of large joints (e.g., knee). For smaller joints (e.g., finger), either hydrocortisone or methylprednisolone (Hydeltrasol, brand no longer available in the United States) is recommended. Tables 5 and 645 compare commonly available steroid preparations.
|Steroid||Common concentration (mg per mL)||Common equivalent dose* (mg)||Approximate duration of action (days)|
|Methylprednisolone acetate (Depo-Medrol)||40 or 80||40||8|
|Triamcinolone acetonide (Kenalog)||10 or 40||40||14|
|Triamcinolone hexacetonide (Aristospan)||20||40||21|
|Dexamethasone acetate (Decadron LA†)||8||8||8|
|Dexamethasone sodium (Decadron†, Solurex†)||4||8||6|
|Joint||Steroid dose* (mg)||Anesthetic dose† (mL)||Needle length (inch)||Needle gauge|
|Shoulder||20 to 40||5||1.5||21|
|Wrist||20 to 40||3||0.5 to 1.5||23 or 25|
|Knee||20 to 80||5||1.5||21|
|Ankle||20 to 40||3 to 5||1.0 to 1.5||23|
Local anesthetics are often combined with corticosteroids for intra-articular injection. Local anesthetics relieve pain and can be used diagnostically to differentiate between local and referred pain.30,46,47 They also add volume to the injectate and help to distribute cortico-steroid within the joint space. Most local anesthetics are short-acting (Table 7).
|Medication||Onset of action (minutes)||Duration of action (hours)||Max volume of injection*|
|0.25% Bupivacaine (Marcaine)||30||8||60 mL|
|0.5% Bupivacaine||30||8||30 mL|
|1% lidocaine (Xylocaine)||1 to 2||1||20 mL|
|2% lidocaine||1 to 2||1||10 mL|
As with the choice of corticosteroids, the choice of local anesthetic for injection is based more on clinical preference than evidence. When corticosteroids and local anesthetics are used together, many patients will experience relatively rapid relief of symptoms following the injection. This is the initial action of the local anesthetic. Patients then often experience a transient increase in pain as the local anesthetic wears off. Longer-term symptom relief results as the injected corticosteroid takes effect. It is helpful to provide this anticipatory guidance to patients before the injection.