Sonographic Mulder sign

Last revised by Yuranga Weerakkody on 26 Apr 2022

The sonographic Mulder sign is the ultrasound correlate of the clinical Mulder sign during examination of the forefoot to investigate causes of metatarsalgia associated with Morton neuroma 1. The intermetatarsal space is predominantly composed of fat inferiorly and also contains the neurovascular bundle, not easily seen on sonography 2. Compression of the metatarsal heads causes displacement of the hyperechoic fat and visualization of a hypoechoic mass in the intermetatarsal space 1. When this is seen, sonographic Mulder sign can be performed to increase diagnostic accuracy 1.


Place the patient prone with feet resting on the bed allowing for the examiner's non-imaging hand to rest on the bed for stability. Hold the patient's foot in the non-imaging hand with the metatarsal heads forming an imaginary line from the thenar eminence to the middle finger. Apply the transducer to the plantar surface of the intermetatarsal spaces and assess each space individually in the coronal and sagittal planes 1.

On identification of the suspicious lesion, apply some pressure with the transducer in the coronal plane lodging the mass between the metatarsal heads 1. Squeeze the metatarsal heads together while concurrently relieving the pressure of the transducer. The mass will displace towards the plantar surface and a palpable click may be felt along with eliciting symptoms.

History and etymology

Jacob D Mulder was a Dutch surgeon who first described his eponymous clinical sign associated with Morton neuroma in 1951 1. The sonographic Mulder sign was first described in 2003 by Martin Torriani and Susan V Kattapuram, musculoskeletal radiologists at Massachusetts General Hospital 1.

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