Thickening of the Intramuscular Fascia of the Iliacus Muscle as Evidence of Myofascial Pathology: A New Hip Pain Syndrome.

Introduction: Hip/inguinal pain is a common symptom in athletes. Ultrasound (US) examination may discriminate causes, among which the iliopsoas muscle is often neglected. In the present case series study, we describe five patients with hip/inguinal pain where an accurate US evaluation of the iliopsoas muscle showed that the origin of the pain was due to alterations of the iliopsoas muscle complex, particularly of the fascia surrounding the medial fibers of the iliacus muscle (MFIM). We describe a novel pathological entity characterized by myofascial rigidity and hip/inguinal pain with thickening of the intramuscular fascia of the iliacus muscle and its epimysium, with increased stiffness of the muscle.

Methods: We studied five athletes with hip/inguinal pain on hip flexion-extension in the absence of hip and visceral pathologies. US was performed with linear probes studying the affected hip at the inguinal level, using longitudinal and axial scans. The examination was completed with power Doppler (PD), strain elastosonography (ELS), and strain ratio (SR) evaluation of the lateral and medial belly of the iliacus muscle.

Results: In all patients, we observed a thickening of the intramuscular fascia that surrounds the medial belly of the iliacus muscle. The mean ± standard deviation thickness of the intramuscular fascia of the iliacus muscle varied significantly between the affected and non-affected sides (2.70 ± 0.41 mm vs. 1.02 ± 0.15 mm, p value 0.012). In two out of five cases, an increase in the intramuscular perifascial vascular signals at PD was detected. All cases showed stiffness of the MFIM on ELS and altered SR in MFIM compared with the lateral ones in three out of five patients.

Conclusions: We describe a novel cause of a pathological condition of the iliopsoas muscle due to the thickening of the medial belly of the iliacus muscle, easily verifiable with US. All subjects responded to physical therapy with high-energy laser and stretching of the muscle unit. Video available for this article.