Bring somebody to their knees
Definition 1 of 2
Pro Tip 1/3Figurative Use
The phrase often describes a non-physical defeat or submission, not an actual person falling down. 
The relentless competition brought the company to its knees.
Pro Tip 2/3Severity of Situation
It implies a very difficult or desperate situation that's hard to recover from. 
Sanctions have brought the nation's economy to its knees.
Pro Tip 3/3Colloquial Expression
Used informally, more common in spoken language or narrative styles. 
After hours of negotiations, the workers' strike brought the city to its knees.