go to see someone like bike whisperer, he might help you adjusting your bike so it fits better, but it's more likely that it's incorrect size and you'll be advised to get a new one,
do it so you'll know which size to buy
56 sounds very small for someone 6'1, you can't get the right advice here though, if you have read what people been posting here you'll know that even 0,5 cm makes a huge difference
you should get a proper bike fit especially if you're already having a knee pain
go to see someone like bike whisperer, he might help you adjusting your bike so it fits better, but it's more likely that it's incorrect size and you'll be advised to get a new one,
do it so you'll know which size to buy
56 sounds very small for someone 6'1, you can't get the right advice here though, if you have read what people been posting here you'll know that even 0,5 cm makes a huge difference
you should get a proper bike fit especially if you're already having a knee pain