Hi Linh,
I think these are 2 seperate issues.
If there is tendon (FPL) bunching or triggering this is almost always caused by A1 hypertrophy and then some underlying FPL tenosynovitis and it will cause a clinical trigger.
In these cases we treat the tenosynovitis with a tendon sheath catabolic injection.
The key to this diagnosis is the abnormal FPL movement and clear evidence of bunching caused buy the A1 pulley.
The click in the IP joint I think is much less important and not associated with the pulley disease or the tenosynovitis.
The A1 is at MCP level not the IP level.
A click in the IP joint is really common and is usually just a nitrogen release inside the joint capsule. It causes a sharp click when flexed just the same as many joints around the body. It is usually asymptomatic and unrelated to pathology. If they have OA in the joint they may have symptoms, but the sharp sounding click is a red herring.
The nitrogen release is caused by creating negative pressure inside the joint capsule and nitrogen is released from the synovial fluid. If you scan it sometimes you can see the gas “flash” when it clicks.
Steve