Elbow Joint Ultrasound: Protocol, Positions, and Dynamic Tests

Why a Standardized Protocol is Needed

Elbow joint ultrasound is often prescribed for pain in the epicondyle area, tendon injury, suspected effusion, bursitis, ulnar nerve compression, or snapping elbow. Standardization is needed not for a formal listing of images but for reproducibility: the same set of zones should allow examination of the joint, tendons, ligaments, nerves, and periarticular soft tissues.

In the current parameter AIUM Practice Parameter for the Performance of a Musculoskeletal Ultrasound Examination, 2023, musculoskeletal ultrasound is described as an examination performed depending on the clinical task, with documentation of relevant anatomy and pathological changes. For the elbow, it is practically convenient to use 4 anatomical zones: anterior, medial, lateral, and posterior.

General Examination Algorithm

The examination begins with clarifying the clinical task: pain, injury, movement limitation, click, neurological symptoms, swelling, or monitoring a known lesion. Then, the area of pain is reviewed, and standard scanning of the elbow in longitudinal and transverse planes is performed. If the symptom is unilateral, it is useful to compare with the opposite elbow, especially in cases of structural variants, questionable tendon hyperechogenicity, or dynamic nerve instability.

The transducer is chosen to achieve maximum spatial resolution for superficial structures. Depth, focus, gain, and Doppler settings are adapted to the object being examined. Transducer pressure should be minimal when assessing fluid, bursae, superficial veins, and painful areas, otherwise, small effusions or hyperemia may be underestimated.

Classification of Elbow Zones by Protocol

Anterior Position

The anterior approach begins with the cubital fossa. In the longitudinal plane, the contours of the humerus, radius, and ulna in the accessible zone, the anterior joint compartment, and the distal biceps tendon are evaluated. In the transverse plane, the course of the tendon, its attachment, surrounding tissue, and possible fluid are checked. In case of injury, it is important not to limit to the site of pain: retraction, hematoma, or partial defect may be located proximal to the zone of maximum tenderness.

The anterior compartment is also convenient for assessing intra-articular fluid if visualized in the joint recess. Doppler is used according to the clinical task: in suspected active inflammatory process, synovial hyperemia, or soft tissue complication. The protocol describes the presence or absence of effusion, synovial thickening, tendon defect, peritendinous changes, and tenderness upon transducer compression.

Medial Position

The medial approach is oriented towards the medial epicondyle. In the longitudinal plane, the common flexor tendon is evaluated from its bony attachment distally, its fibrillarity, local tenderness, and peri-entheseal changes. The medial collateral complex, primarily its accessible superficial components, is visualized nearby. In case of injury or overload, the protocol should document the side, precise localization, and dynamic response to stress.

The cubital tunnel is assessed separately. The ulnar nerve is traced in the transverse plane proximally, at the level of the groove, and distally to the canal, then in the longitudinal plane. The conclusion should not replace description with non-existent universal numerical norms: AIUM 2023 does not set a threshold for area or diameter for the ulnar nerve at the elbow. Significant are shape, echostructure, compression, tenderness, comparison with the healthy side, and dynamic displacement.

Lateral Position

The lateral approach includes the lateral epicondyle, common extensor tendon, and radiocapitellar zone. Scanning is performed along the long axis of the tendon and transversely to avoid mistaking anisotropy for pathological hypoechogenicity. In case of lateral pain, enthesis, thickness, and structure of the tendon mass are documented descriptively, as well as the presence of tears, calcifications, perifocal fluid, or Doppler signal with appropriate settings.

The lateral ligament complex and annular ligament are evaluated within the available ultrasound anatomy. If the complaint is related to instability or painful snapping, a static image is insufficient: the physician must reproduce the provoking movement in a safe range and show which structure is displaced or impinged.

Posterior Position

The posterior approach focuses on the triceps tendon, olecranon, posterior joint compartment, and olecranon bursa. The triceps tendon is examined longitudinally from the musculotendinous junction to the attachment and transversely across its entire width. In case of injury, fiber continuity, retraction, hematoma, and involvement of superficial soft tissues are described.

The olecranon bursa may be unremarkable in the absence of fluid; in bursitis, the protocol reflects content, wall, septa, compressibility, and Doppler signs of inflammation. The posterior joint compartment is assessed for effusion and synovial changes, especially if clinically there is extension limitation or pain in terminal positions.

Dynamic Tests

The dynamic part is a key advantage of elbow ultrasound. The minimal set is selected based on the complaint: flexion-extension for the ulnar nerve and posterior structures, valgus stress for the medial side, provocative movements for lateral pain or snapping. The test should be recorded or documented with a series of images before, during, and after movement.

When assessing the ulnar nerve, it is important to observe its position relative to the medial epicondyle during flexion and extension. The preservation of position, subluxation, dislocation, associated displacement of the medial head of the triceps, and symptom reproduction are described. In medial instability, it is noted whether a stress test was performed and what changed relative to rest and the opposite side.

What to Include in the Protocol

• Indication for the examination and side.
• Type of examination: complete for 4 zones or focused on the clinical task.
• List of examined zones: anterior, medial, lateral, posterior.
• Description of tendons, ligaments, joint recesses, bursae, nerves, and soft tissues if they are relevant to the complaint.
• Presence of effusion, synovial changes, tear, tendinopathy, bursitis, mass, or dynamic instability.
• Results of dynamic tests and the connection of findings with pain or snapping reproduction.
• Comparison with the contralateral side if performed.

Typical Errors

The main errors in elbow ultrasound are related to incomplete zone coverage and lack of dynamics. In lateral pain, often only the common extensor tendon is evaluated, missing the radiocapitellar joint. In medial pain, only the flexor tendon is described, without checking the ulnar nerve and response to valgus stress. In suspected bursitis, excessive transducer pressure can reduce the visible fluid volume.

Another error is numerical categorization without a source. The AIUM 2023 parameter sets requirements for performing and documenting the examination but does not establish universal millimeter thresholds for elbow tendons, ligaments, bursae, or the ulnar nerve. Therefore, a correct conclusion should be anatomically accurate and reproducible, not based on unverified local 'norms'.