What is that tie on their knees

Hi 

Yesterday I was watching a match zhang jike vs Wang and I was watching there footwork really carefully so I notes that there were a small red tie around there knees and I saw that tie many times with zhang but I still dont know anything about it I don't know if you saw it but I think it is an injection or some thing they had it when they. Were young and training because to be in this high level you really need a lot of training and painful injections is not it 

Thanks a lot 

Yasir

Hi Yasir,

It will just be a support for their knees.  They do so much training that their knees are under a lot of strain.