There are all kinds of acute injuries the knee can sustain while playing tennis like ligament and meniscus tears.  These types of injuries typically occur due to shearing rotational forces placed on the joint during deceleration.  In my humble opinion,I believe acute knee injuries are closely connected to the lack of reactive trunk stability.  So if you are interested in trying to prevent these injuries squats and leg presses will not get the job done.  Get the job done by spending time reactively training the trunk.

Take a look at the video below to see what I mean along with some really simple band exercises designed to get the trunk on board and prevent these types of injuries.