Why have i developed pain in what's feels like the joint connecting my thumb to my wrist and sometimes my thumb locks up?

Tendon or joint?: This sounds a s if it is basilar joint arthritis. This is a common condition and should be evaluated by a qualified hand surgeon with an examination and x-ray. There are many potential other causes. Initial treatment may be with rest, splint, anti-inflammatories and/or joint injections (rare). Advanced cases may benefit from surgery but you should first identify the precipitating cause.

May be trigger thumb: The two most common causes pain in the joints of the thumb are stenosing tenosynovitis or trigger thumb and arthritis at the base of the thumb. At your young age, and with symptoms of locking, it's much more likely that this is due to a trigger thumb. This can often be treated simply with a splint at night or a steroid injection. You should see a hand specialist for evaluation. \.