If you feel any pain in the base of your thumb or 3rd or 4th fingers (ring and little finger), it may be an early sign of something called trigger finger (it can also be arthritis, but we'll get to that later).
As the condition worsens, you'll find it harder to bend one or more of those fingers (it can occur on either hand), and it may also get stuck in a bent position. The finger can sometimes free itself, in which case it will pop back to its normal position (often with a sound). Hence the name trigger finger.
The cause of trigger finger is not clear, but what happens is that the sheath through which the tendon runs can swell up (as can the tendon itself) and cause the tendon to stop flowing freely.
It's also possible for the tendon to not just get stuck but to contract or recoil on itself causing a major obstacle to movement of the finger. That's what's happening when the finger locks up completely.
For many people, a steroid injection into the affected joint will be sufficient to reduce the swelling and allow the finger to move again, but further injections may also be necessary.
If an injection does not work and no further action is taken, the affected finger may get worse to the point that recovery after surgery is less guaranteed. Your consultant will bring up all these points with you during your consultation.