Presentation
Painful thumb with triggering.
Patient Data











Thickening of the thumb A1 pulley with adjacent focal high signal and mild bulging of the flexor pollicis longus tendon (reflecting a nodule) and a proximal thin tendon sheath effusion.
Extensor pollicis longus and abductor pollicis brevis tendons are intact.
First carpometacarpal joint osteoarthritis with joint effusion and synovial thickening. Thumb metacarpophalangeal and interphalangeal joints are unremarkable.
Case Discussion
MRI is not often performed as the clinical diagnosis of trigger thumb is usually fairly straightforward. The MRI findings of trigger thumb are often subtle, in this case, there is a small nodule of the flexor pollicis longus tendon with thickening of the A1 pulley and a very thin tendon sheath effusion more proximally. Being aware of the mismatch between relatively subtle MRI findings and the more obvious clinical signs is important.