pokleknuti

1. (pred + instr.) to give in; to yield; to cave in
   Vlada je na kraju pokleknula pred pritiskom javnosti. — The government eventually gave in to public pressure.
   Nije pokleknuo ni kad su mu pretili. — He didn't cave in even when they threatened him.
2. (of a team, player) to falter; to crack
   Naši su pokleknuli u poslednjoj četvrtini. — Our team faltered in the last quarter.
3. (of knees, legs) to buckle; to give way
   Kolena su mi pokleknula od umora. — My knees buckled from exhaustion.

In the sense 'give in' it is usually used with pred + instrumental: pokleknuti pred pritiskom.