Ultrasound of the Adult Hip Joint: Protocol, Effusion, Synovitis

Reference to Primary Source

The practical protocol for ultrasound of the adult hip joint is advisable to be based on the general standard AIUM Practice Parameter for the Performance of a Musculoskeletal Ultrasound Examination, 2023. The document does not describe a separate 'table of norms' for each joint but outlines the requirements for performing musculoskeletal ultrasound: choice of transducer, scanning in longitudinal and transverse planes, assessment of joints, tendons, muscles, ligaments, bursae, nerves, soft tissue formations, use of dynamic tests, and Doppler as per clinical task.

For adults, this fundamentally distinguishes the examination from infant hip ultrasound by Graf: in adults, alpha and beta angles are not assessed, but the clinical question is answered — is there effusion, synovitis, bursitis, tendinopathy, rupture, soft tissue impingement, or a cause of local pain.

Clinical Tasks of Adult Hip Joint Ultrasound

Main tasks: confirm or exclude intra-articular effusion; describe signs of synovial thickening and hypervascularization; assess the tendon-muscle apparatus around the joint; identify bursitis; localize the painful area before puncture or injection; distinguish joint-related pain from periarticular.

Ultrasound is especially useful for groin pain, lateral pain over the greater trochanter, suspected effusion post-surgery or trauma, inflammatory arthropathies, painful clicking, local swelling, suspected pathology of the iliopsoas, gluteal, adductor tendons, or proximal hamstrings.

Examination Technique

AIUM recommends using a transducer with the most suitable frequency for depth and body habitus. In slender patients, anterior and lateral structures are accessible with a linear transducer; for deep joint location, significant muscle mass, or obesity, a transducer with greater penetration depth is needed. Frequency need not be specified in the conclusion, but it is useful to record the type of transducer and modes in the local protocol.

Each symptomatic area is assessed in long and short axes. Images should document normal and pathological structures, and in case of ambiguity, contralateral comparison. Doppler is applied when it is necessary to assess inflammatory activity, synovial hyperemia, vascularity of a soft tissue formation, or to distinguish fluid from vascularized tissue. Dynamic tests are performed for clicking, tendon subluxation, impingement, or pain reproducible by movement.

Anterior Approach: Effusion and Synovitis

The key approach for effusion is anterior, along the long axis of the femoral neck. Landmarks include the femoral head and neck, anterior capsule, iliopsoas muscle, and tendon. The protocol describes the anterior joint recess: is there anechoic or complex fluid content, capsule deformation, synovial thickening, intra-articular echogenic inclusions, tenderness on transducer compression.

AIUM 2023 does not establish a universal numerical threshold for diagnosing effusion in the adult hip joint. Therefore, local 'norms' should not be mechanically transferred into the protocol without specifying the source. It is practically significant to indicate: effusion is absent or present; minimal, moderate, or pronounced by visual assessment; homogeneous or complex; is there synovial proliferation and Doppler signal. If measuring the depth of the fluid layer or capsular bulging is performed, it should be reproducible, in the same plane, and preferably with comparison to the opposite side.

Tendons and Bursae Around the Hip Joint

The anterior section includes the iliopsoas muscle and tendon, as well as the area of the iliopsoas bursa. In groin pain, describe thickening, fibrillar disruption, partial or complete rupture, fluid in the bursa, tenderness on compression, and dynamic tendon conflict during movement.

The lateral section is the area of the greater trochanter. Here, the tendons of the gluteus medius and minimus muscles, the cortical contour of the greater trochanter, peritendinous fluid, and trochanteric bursae are assessed. In lateral pain syndrome, it is important not to limit to the word 'bursitis': it is often necessary to describe whether there is tendinopathy, enthesopathy, calcifications, tendon rupture, retraction, muscle belly atrophy, or isolated fluid in the bursa.

The medial section is examined for pain in the adductor group: assess the adductor tendons, muscle injuries, and the pubic symphysis area within ultrasound accessibility. The posterior section includes the ischial tuberosity, proximal hamstring tendons, ischial bursa, and the area of the sciatic nerve if it corresponds to complaints.

Protocol Table

Doppler and Dynamic Tests

Doppler is not an 'automatic' criterion for arthritis but enhances the value of the study when active synovitis, infectious process, inflammatory arthropathy, or hypervascular soft tissue formation is suspected. Describe not only the presence of the signal but also its location: in the synovium, in the bursa wall, peritendinous, or in soft tissues.

Dynamic assessment is needed for the clicking symptom, suspected mobile conflict of the iliopsoas tendon, provocation of pain in the lateral zone, or assessment of tendon gliding. The protocol records whether the clinical symptom is reproduced during the maneuver and which structure shifts or conflicts at that moment.

How to Formulate the Conclusion

The optimal conclusion should be concise and clinically applicable. Example structure: 'Anterior recess of the right hip joint: effusion with heterogeneous content is determined; synovial membrane is thickened, vascularization is increased on Doppler examination. Signs of tendinopathy of the gluteus medius tendon without complete rupture. Fluid in the trochanteric bursa. Ultrasound signs of synovitis of the right hip joint and lateral pain syndrome of the greater trochanter.'

If there is no effusion, this should also be clearly stated: 'No ultrasound signs of effusion in the anterior recess.' In case of limited visualization, the reason should be written: deep joint location, postoperative changes, significant pain syndrome, inability to perform dynamic test.

Method Limitations

Ultrasound shows fluid, synovial membrane, tendons, bursae, and superficial soft tissues well, but is limited for deep intraosseous pathology, bone marrow, cartilage in inaccessible areas, and complete assessment of the acetabular labrum. If osteonecrosis, stress fracture, intraosseous tumor, complex postoperative problem, or pathology extending beyond the acoustic window is suspected, another imaging method is required.

The main mistake is substituting the adult protocol with the Graf infant scheme or limiting to one anterior image without assessing periarticular tendons. The second mistake is using a numerical effusion threshold without specifying a validated source. Within AIUM 2023, it is more correct to provide a reproducible description and clinically oriented localization of the finding.