Clinical significance of signal changes in the quadratus femoris muscle on MR

To evaluate the clinical significance of quadratus femoris muscle signal changes (QFMC) on MRI. 204 consecutive bilateral MRI hip examinations (132 female, 72 male) were reviewed in retrospect for QFMC. Inclusion imaging parameters were edema or atrophy of the quadratus femoris muscle. The presence or absence of symptoms and additional ipsilateral and/or contralateral imaging findings were used to differentiate between isolated symptomatic, co-incidental and asymptomatic QFMC. 24 (11.8%) patients and 30 (7.3%) hips demonstrated QFMC. Atrophy was present in 5 symptomatic hips. Female to male ratio was 23:1. Isolated symptomatic QFMC: 4 hips (13.3%), 1 bilateral. Clinical symptoms in this group were non-specific greater trochanter pain and stiffness of the hip. Co-incidental QFMC: 19 symptomatic hips, ipsilateral associated findings present in 18 hips (94.7%) and contralateral additional findings present in 8 hips (42.1%). Asymptomatic QFMC: 7 hips (23.3%), ipsilateral associated asymptomatic findings in 5 hips (71.4%) and contralateral associated symptomatic findings in 6 hips (85.7%). Edema around the greater trochanter and hamstring insertions were the most frequent associated findings. In this study, most cases of QFMC were co-incidental or asymptomatic. In isolated symptomatic QFMC clinical complaints were non-specific. Atrophy was found only in the symptomatic hips.