55-year-old patient with persistent complaints in the left hip region. The patient has a history of a previous Morel-Lavallée lesion in the same region and known degenerative hip osteoarthritis. Previous intra-articular hip injections provided only short-lasting symptom relief.
Ultrasound examination of the investigated hip region demonstrates mild distension of the hip capsule, compatible with a small intracapsular effusion or synovial swelling, grade 1.
At the femoral head-neck junction, the cortical bone contour is irregular, with a visible osteophyte. These findings are in keeping with known degenerative coxarthrosis.
The region of the previous Morel-Lavallée lesion appears quiescent. There is no recurrent fluid collection, no rupture, no hyperemia, and no sonographic evidence of active inflammation in the examined soft tissues.
The persistent symptoms are therefore more likely related to an intra-articular pain source associated with hip osteoarthritis than to recurrence of the former Morel-Lavallée lesion or active extra-articular soft tissue pathology.
1. Final diagnosis
Sonographic findings are consistent with known hip osteoarthritis, with mild capsular distension and degenerative osseous changes. No evidence of recurrent Morel-Lavallée lesion or active inflammatory soft tissue abnormality is present.
2. Differential diagnosis
The main differential diagnosis is symptomatic coxarthrosis with recurrent synovial irritation and a small effusion. Other possible intra-articular pain sources include chondral damage, labral degeneration, or femoroacetabular impingement-related symptoms, although ultrasound is limited for evaluating these abnormalities. Residual post-traumatic or postoperative symptoms without active sonographic soft tissue pathology may also be considered.
3. Teaching points
Mild hip capsular distension on ultrasound can reflect low-grade synovial irritation or effusion in degenerative hip disease. Careful assessment of the extra-articular soft tissues is important in patients with a previous Morel-Lavallée lesion, as recurrence typically presents as a definable fluid collection. In this case, the absence of recurrent fluid, hyperemia, or soft tissue inflammation supports an intra-articular rather than extra-articular pain source.
4. Injury/disease information
Hip osteoarthritis is a degenerative joint disorder characterized by cartilage loss, osteophyte formation, capsular irritation, and progressive pain or functional limitation. Ultrasound can demonstrate secondary findings such as capsular distension, effusion, synovial thickening, and accessible bony osteophytes, but it cannot reliably assess cartilage, labrum, or deep intra-articular morphology. When injection therapy is considered, ultrasound-guided intra-articular hip injection is preferred for accurate needle placement. Hyaluronic acid injections are not routinely recommended for hip osteoarthritis because their clinical benefit remains insufficiently established.
Marc is founder of, and trainer at, SonoSkills. SonoSkills is an organization dedicated to MSK ultrasound education. He's also an MSK Sonographer at EchoConsult in Roermond, the Netherlands.
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