Beginner Knee Strengthening Exercises. The best way to strengthen weak knees is to build the muscle supporting them. Consult your doc or physio if you have knee pain. For FULL-LENGTH beginner and intermediate videos, sign up to my online courses at courses.justinagustin.com! Exercise from the comfort of your own home with zero gym equipment! #fitness #motivation #fit #kneepain #health #kneehealth