Knee injuries are very common in squash, and sometimes take a lot of time to recover from.
To protect from your knees from injury and pain, it is very important to strengthen the muscles surrounding your knees, as well as your hips. It is imperative for increasing speed, agility and endurance in squash, as well as to support the joint surfaces so over many years of playing, they do not suffer from overuse.
When starting any new exercise, start slowly
and only gradually add repetitions, time and level of difficulty.