Residency · Residency · Chronic Pain Management
Joint Injections: Knee, Hip, and Shoulder
Introduction
Intra-articular injections are among the most frequently performed interventional procedures in pain medicine, serving both diagnostic and therapeutic purposes. The knee, hip, and shoulder are the three most commonly injected large joints, each with distinct anatomical considerations, approach techniques, and evidence bases. Mastery of both landmark-based and ultrasound-guided techniques is essential for the pain medicine trainee.
General Principles
Indications
The most common indication is osteoarthritis (OA), where injections provide symptomatic relief when conservative measures fail. Other indications include inflammatory arthropathies (rheumatoid arthritis, crystalline arthropathies such as gout and pseudogout, and psoriatic arthritis), adhesive capsulitis (particularly in the shoulder, combined with physical therapy), and diagnostic purposes to confirm that a joint is the pain generator when clinical and imaging findings are equivocal.
Contraindications
Absolute contraindications include overlying skin infection, bacteremia, joint prosthesis without orthopedic consultation, and known hypersensitivity to the injectate. Relative contraindications include coagulopathy (INR greater than 1.5 or platelets below 50,000), uncontrolled diabetes mellitus, and an unstable joint.
Injectable Agents
The main injectable agents are corticosteroids (triamcinolone acetonide 40 mg, methylprednisolone acetate 40-80 mg, or betamethasone 6 mg), hyaluronic acid (viscosupplementation with high-molecular-weight hyaluronan derivatives), platelet-rich plasma (autologous concentrated platelets with growth factors), and local anesthetics (lidocaine or bupivacaine, mixed with corticosteroid for immediate pain relief and diagnostic confirmation).
| Joint | Landmark Accuracy | US-Guided Accuracy | Most Common Approach | Key Anatomic Concern |
|---|---|---|---|---|
| Knee | ~79% | ~96% | Superolateral (suprapatellar recess) | Largest joint cavity; effusion common |
| Hip | 60–80% | ~97% | Anterior (femoral head-neck junction) | Deep joint; femoral neurovascular bundle |
| Shoulder (GH) | ~85% | ~99% | Posterior (posterior joint recess) | Rotator cuff; axillary nerve |
Knee Joint Injection
Anatomy
The knee is a synovial hinge joint with the largest joint cavity in the body. The suprapatellar bursa communicates with the joint space and serves as a common injection target. Key landmarks include the patella, medial and lateral femoral condyles, and the tibial plateau.
Landmark-Based Approaches
The superolateral approach is the most common: with the patient supine and knee extended, the needle is inserted 1 cm superior and 1 cm lateral to the superolateral corner of the patella, directed 45 degrees inferiorly and medially beneath the patella. The lateral midpatellar approach inserts the needle at the midpoint of the lateral patellar border, directed horizontally toward the intercondylar notch. The anteromedial/anterolateral approach, performed with the knee flexed 90 degrees, inserts the needle adjacent to the patellar tendon, just medial or lateral to it.
Ultrasound-Guided Technique
The most common ultrasound-guided approach targets the suprapatellar recess, with the transducer placed in long axis over the suprapatellar region and the needle advanced in-plane into the suprapatellar bursa. This allows real-time visualization of effusion, needle tip placement, and injectate distribution, and significantly improves accuracy compared to landmark techniques (96% versus 79%).
<image>Ultrasound-guided suprapatellar knee injection illustration showing a longitudinal sonographic view of the suprapatellar recess with the ultrasound transducer positioned on the anterior distal thigh, a needle advancing in-plane into the suprapatellar bursa filled with anechoic fluid, and labeled anatomical structures including the quadriceps tendon, prefemoral fat pad, suprapatellar bursa, femoral cortex, and patella</image>
Hip Joint Injection
Anatomy
The hip is a deep ball-and-socket synovial joint surrounded by a thick fibrous capsule and dense musculature. The femoral head articulates with the acetabulum, and the joint is reinforced by the iliofemoral, pubofemoral, and ischiofemoral ligaments. The critical neurovascular structures include the femoral artery, vein, and nerve, remembered by the "NAVEL" mnemonic (lateral to medial: nerve, artery, vein, empty space, lymphatics).
Landmark-Based Approach (Anterior)
With the patient supine, the femoral artery pulse is identified at the inguinal crease. The needle is inserted 2-3 cm lateral to the femoral artery and 2-3 cm distal to the inguinal ligament, directed posteriorly and slightly medially until bony contact with the femoral neck is made. Fluoroscopic guidance is strongly recommended due to the depth of the joint and proximity to neurovascular structures.
Ultrasound-Guided Technique
For the anterior approach, the transducer is placed in long axis over the femoral head-neck junction, and the needle is advanced in-plane from lateral to medial targeting the anterior synovial recess. The needle tip is visualized piercing the joint capsule with real-time sonography, and color Doppler is used to identify and avoid the femoral artery and circumflex vessels.
Special Considerations
Landmark-based hip injections have the lowest accuracy among major joints (60-80%) without image guidance. Fluoroscopy with contrast confirmation remains the gold standard for confirming intra-articular placement, while ultrasound guidance accuracy approaches 97% in experienced hands.
<image>Anterior anatomical cross-section of the hip joint during ultrasound-guided injection, showing the needle trajectory from the anterior skin surface passing lateral to the femoral neurovascular bundle, through the iliopsoas muscle, piercing the anterior hip joint capsule, and entering the anterior synovial recess at the femoral head-neck junction, with labeled structures including the femoral artery and nerve, iliopsoas tendon, anterior labrum, femoral head, and acetabulum</image>
Shoulder Joint Injection
Anatomy
The glenohumeral joint is a shallow ball-and-socket joint with the greatest range of motion in the body. The glenoid labrum deepens the glenoid fossa, and the joint is stabilized primarily by the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) and the glenohumeral ligaments.
Posterior Approach (Landmark-Based)
The patient is seated with the arm in neutral position or slight internal rotation. The posterolateral corner of the acromion is palpated, and the needle is inserted 2-3 cm inferior and 1 cm medial to the posterolateral acromion, directed anteriorly and medially toward the coracoid process. A "give" or loss of resistance is felt as the needle enters the joint capsule.
Ultrasound-Guided Posterior Approach
The transducer is placed in the axial plane over the posterior glenohumeral joint, and the humeral head, posterior labrum, and infraspinatus muscle are visualized. The needle is advanced in-plane from lateral to medial into the posterior joint recess. Ultrasound guidance improves accuracy from approximately 85% to 99%.
Subacromial-Subdeltoid Bursa Injection
This is a common target for rotator cuff pathology and subacromial impingement. Using a lateral approach, the needle is inserted just inferior to the lateral acromion and directed medially beneath the acromion. This is a bursal injection, not a true intra-articular injection, and should be distinguished during documentation.
Injectate Comparison: Evidence
Corticosteroids
Corticosteroids provide short-term relief (2-6 weeks) for OA and inflammatory arthropathies. Meta-analyses demonstrate superiority over placebo at 1-4 weeks but no benefit beyond 6 months. Importantly, McAlindon et al. (JAMA 2017) showed that triamcinolone injections every 3 months led to significantly greater cartilage volume loss than saline over 2 years. Injections should be limited to 3-4 per joint per year with at least 3-month intervals.
Hyaluronic Acid
The proposed mechanism of hyaluronic acid is restoration of the viscoelastic properties of synovial fluid along with reduction of inflammation. AAOS guidelines provide a limited recommendation against viscosupplementation for knee OA, and a Cochrane review shows a small benefit over placebo with high heterogeneity among preparations. Hyaluronic acid may be considered when corticosteroids are contraindicated, such as in uncontrolled diabetes.
Platelet-Rich Plasma (PRP)
PRP contains concentrated growth factors (PDGF, TGF-beta, VEGF, IGF-1) that may promote tissue healing. Leukocyte-poor (LP-PRP) preparations may be preferred for intra-articular use to reduce the inflammatory response. Meta-analyses suggest PRP provides superior pain relief to hyaluronic acid and corticosteroids at 6-12 months for knee OA. However, PRP is not yet covered by most insurance plans, and variable preparation protocols limit comparability across studies.
<image>Comparative diagram showing three syringes with their respective injectate contents for joint injection — corticosteroid suspension (milky white), hyaluronic acid gel (clear viscous), and platelet-rich plasma (golden-yellow) — alongside a summary table comparing mechanism of action, onset of relief, duration of benefit, evidence grade, and potential adverse effects for each agent in the treatment of knee osteoarthritis</image>
Complications
Septic arthritis is rare (1 in 10,000-50,000 injections) but devastating, making strict aseptic technique paramount. Post-injection flare occurs in 2-5% of corticosteroid injections due to crystal-induced synovitis from steroid particles and is self-limited over 24-48 hours. Soft tissue atrophy and depigmentation can occur with superficial corticosteroid deposition. Corticosteroids elevate blood glucose for 2-5 days, so diabetic patients should be counseled accordingly. Direct corticosteroid injection into tendons should be avoided due to the risk of tendon weakening.
Clinical Pearls
Aspiration before injection is recommended for any joint with significant effusion — fluid should be sent for cell count, crystal analysis, gram stain, and culture when infection is suspected. For the knee, the superolateral approach with ultrasound guidance provides the highest accuracy and is the preferred technique in most settings. Hip injections should always be performed with image guidance (ultrasound or fluoroscopy) given the depth of the joint and risk to neurovascular structures. After corticosteroid injection, patients should rest the joint for 24-48 hours and avoid strenuous activity for 1 week. When comparing injectates for knee OA, discuss the time course of benefit with patients: corticosteroids offer rapid but short-lived relief, while PRP may provide longer-lasting benefit with a delayed onset.
References
- Kompel AJ, Roemer FW, Murakami AM, Diaz LE, Crema MD, Guermazi A. Intra-articular corticosteroid injections in the hip and knee: Perhaps not as safe as we thought? Radiology. 2019;293(3):656-663.
- McAlindon TE, LaValley MP, Harvey WF, et al. Effect of intra-articular triamcinolone vs saline on knee cartilage volume and pain in patients with knee osteoarthritis: A randomized clinical trial. JAMA. 2017;317(19):1967-1975.
- Belk JW, Kraeutler MJ, Houck DA, Goodrich JA, Dragoo JL, McCarty EC. Platelet-rich plasma versus hyaluronic acid for knee osteoarthritis: A systematic review and meta-analysis of randomized controlled trials. Am J Sports Med. 2021;49(1):249-260.
- Daniels EW, Cole LG, Engel M, Hill CL. Ultrasound-guided versus landmark-guided large joint injections: A systematic review and meta-analysis. Arthritis Care Res. 2018;70(6):938-944.
