34-year-old male with posterior hamstring pain for 2 years. Evaluate for proximal hamstring tendon tear and evaluate atrophy of the distal hamstring and possible denervation. As seen on the recent knee MRI examination, there is fatty infiltration of the semimembranosus muscle. The distal tendinous insertion is not included in the field-of-view of this study, but was unremarkable on the prior knee MRI exam. The proximal tendon can be followed to its origin from the ischium and does not appear to be thickened or scarred. There is perhaps minimal fatty infiltration of the distal biceps femoris muscle, but otherwise the biceps femoris and semitendinous muscles appear normal. The remaining musculature of the thigh is normal. On the large field-of-view coronal images, there appears to be fatty infiltration of the right semimembranosus muscle as well. The bone marrow signal intensity is normal.
Idiopathic fatty atrophy of the semimembranosus muscle without findings to confirm a hamstring tendon tear. Of note, this appears to be a bilateral process.