Musculoskeletal conditions are reported by 48% of the population and are a significant component of primary care visits.¹ Joint and soft tissue injections can serve as diagnostic aids and adjunctive treatments (Table 1²). Injections can be categorized as diagnostic or therapeutic. A diagnostic injection clarifies the underlying pathology causing pain. Diagnostic injections introduce a local anesthetic with subsequent evaluation for symptom relief. Aspiration of synovial fluid for substrate analysis is classified as a diagnostic injection; however, it can also be therapeutic for joint effusion or a painful cyst.²

Therapeutic injections provide clinical benefits by relieving pain, restoring function, or both. These injections commonly include corticosteroids, hyaluronic acid, dextrose prolotherapy, and platelet-rich plasma.

Diagnostic and therapeutic injections can be performed with and without imaging guidance; however, imaging guidance increases injection accuracy and is warranted in specific anatomic locations, including the glenohumeral joint, femoroacetabular joint, and nerve hydrodissections.³ Knowledge of anatomy, proper patient positioning, and physician preparedness are essential for all injections. A patient's understanding of risks, benefits, and alternatives promotes patient-oriented outcomes.^4,5

Diagnostic Injections

Diagnostic injections identify which structure is generating pain when nearby structures overlap the pattern of symptoms. For example, a diagnostic injection can accurately identify the cause of shoulder pain in a patient with both glenohumeral and acromioclavicular joint pain features or if conservative management has been ineffective.

Lidocaine, bupivacaine, and ropivacaine (Naropin) are commonly used in diagnostic injections. Anesthetic injections have a dose-dependent potential for cell damage, most prominently with lidocaine and bupivacaine.^6,7 Evidence supports ultrasonography to improve the accuracy of injection of the acromioclavicular joint, biceps tendon sheath, glenohumeral joint, and hip joint.^8–10 A targeted soft tissue diagnostic injection providing immediate relief of more than 50% of preprocedural pain clarifies the diagnosis.

Therapeutic Injections

Therapeutic injections should be used with injury-specific rehabilitation and modification of aggravating activities.¹¹ Table 2 summarizes the evidence-based application of therapeutic injection for musculoskeletal conditions.¹² Other therapeutic injections, such as botulinum toxin, sclerotherapy, mesenchymal signaling, and other cellular therapies are beyond the scope of this article.

CORTICOSTEROID

Indications. High-quality evidence supports the use of corticosteroid injections for adhesive capsulitis, de Quervain tenosynovitis, and trigger finger.^13–17 In a systematic review and network meta-analysis evaluating pharmacologic treatments for adhesive capsulitis, the most significant benefit was found in patients with less than two months of symptoms who had intra-articular glenohumeral corticosteroid injections or corticosteroid injections and capsule distention.¹³ For de Quervain tenosynovitis, tendon sheath corticosteroid injections alone provided greater pain relief compared with corticosteroid injections with splinting, splinting alone, rest, or nonsteroidal anti-inflammatory drugs (NSAIDs) in patients 38 to 50 years of age.¹⁴ In patients who are pregnant and breastfeeding with de Quervain tenosynovitis, corticosteroid injection is superior to thumb spica splinting.¹⁷ In a double-blind, randomized controlled trial (RCT) of 50 patients, tendon sheath corticosteroid injections for trigger finger had a significantly higher success rate compared with normal saline injection in decreasing the frequency of triggering and severity of symptoms.¹⁵

Corticosteroids are also used to treat nerve entrapment (e.g., the median nerve at the carpal tunnel); however, evidence suggests that benefits may be attributed to corticosteroid and physical tissue distortion.¹⁸ Tendinopathies such as gluteus medius (greater trochanteric pain) and common extensor tendinopathy (lateral epicondylopathy, tennis elbow) were previously thought to benefit from corticosteroid injections, but extensive evidence shows that rehabilitation outperforms any combination of treatments, including corticosteroid injections.^19–21 Table 3 offers composition and needle size guidance for commonly performed landmark-guided corticosteroid injections.^12,22–24 Figure 1 provides an example of a setup for a knee injection.