Here are two questions and answers that demonstrate the necessity of having sufficient strength, muscular endurance, and mastery of lead-up skills prior to learning the high roundhouse kick. I have heard that these high repetitions will give knee problems. I am referring to past rumors and then recent personal experience, not anything I have ever seen published. And I have recently been working with kicks such as the Front Toe kick and Roundhouse kick, trying to get power in it from my hips, and I've been noticing a soreness just above the patella and a stiffness in the knees in general. Feels like tendinitis.
Rational training strengthens the body.
It takes a few months of general fitness training before a person is ready for learning fighting techniques. Instructors who allow beginners to practice kicks without going through this basic training set them up for injuries. One of the possible causes of knee and patella problems is insufficient range of rotation in the hip joint during the kick because it changes the patello-femoral tracking. This happens because in the straddle stance the thigh bones are made to face mostly forward while the outside part of the quadriceps pulls at the kneecap. Something similar happens during a kick if the kicker does not have enough range of motion in the hip joint for the required amount of outside rotation of the supporting thigh and the outside part of the quadriceps of the kicking leg is tight.