Thenar longitudinal scan of MCP joint

The patient sits, hand supinated, arm supported. The transducer is placed in an oblique sagittal plane parallel to the long axis of the first metacarpophalangeal bone. The transducer is now moved medially until the flexor pollicis longus tendon is observed.

Skin, subcutaneous fat, flexor pollicis brevis muscle, flexor pollicis longus tendon and adductor pollicis muscle are visualised. Flexion of the thumb allows movement of the flexor pollicis longus tendon in its tendon sheath to be identified.