General Principles of Orthopaedic Injections
An injection should have a clear purpose. It may be diagnostic, therapeutic, or both.
Diagnostic injections
A diagnostic injection is used to help identify the source of pain when symptoms, examination findings, and imaging do not clearly identify the main pain generator.
Examples include local anesthetic injected into the hip joint to help determine whether pain is coming from the hip rather than the lumbar spine, sacroiliac joint, trochanteric region, or surrounding soft tissues. A glenohumeral joint injection may help distinguish shoulder joint arthritis from rotator cuff or subacromial pain. A subacromial injection may help determine whether pain is arising from the subacromial space, rotator cuff tendons, or bursa.
Therapeutic injections
A therapeutic injection is intended to reduce pain, inflammation, irritation, or swelling. Examples include corticosteroid injection for an inflamed arthritic knee, subacromial corticosteroid injection for rotator cuff-related pain or bursitis, trochanteric bursa injection for greater trochanteric pain syndrome, trigger finger injection into the flexor tendon sheath, hyaluronic acid injection for selected cases of knee osteoarthritis, or PRP injection for selected cases of knee osteoarthritis or chronic tendinopathy.
Image-guided versus landmark-guided injections
Some injections can be performed using anatomical landmarks. Others are more accurate and safer when performed with ultrasound or fluoroscopic guidance.
Common image-guided injections include hip joint injections, glenohumeral joint injections, iliopsoas bursa injections, deep trochanteric or peritendinous injections, biceps tendon sheath injections, small joint injections when anatomy is difficult, and peritendinous injections around tendons where avoiding injection into the tendon substance is important.
Ultrasound guidance allows real-time visualization of the needle, target structure, vessels, nerves, tendons, joint fluid, and medication spread. Fluoroscopy is often used for deep joints such as the hip and for spine-related procedures.
Part of a broader treatment plan
Injections are usually combined with other treatments such as activity modification, weight management when appropriate, physiotherapy, strengthening, stretching, anti-inflammatory medication when safe, bracing when appropriate, ergonomic or occupational changes, and treatment of underlying arthritis, tendon overload, or biomechanical contributors.