The best answer to the health and workout question above would be overload. It is evident that the person developed knee pain from running everyday - a sign that the knee was put on a greater amount of stress. This principle of sport training is called the overload and is used to strengthen the ability of that certain muscle to work efficiently.
Quadriceps, hamstrings, biceps,and triceps. is all i can think of right now.
It is home!
Hopes this help