Hello, What it appears to me is it won t be a tendon injury. Rather it will be a ligament sprain. Because your flexion and extension movements as you mentioned are pain-free we have to discard the tendon injury. Also, you mentioned that rotational movement is painful That is because of the ligament injury or maybe muscle getting squeezed in that position. Using a hot water fermentation and avoiding doing exercise for a week or so should help it heal. Once healed you can go back to physical exercise starting with free exercise initially to gain muscle torque and then onto weight bearing. Hope I have answered your query. Let me know if I can assist you further. Regards, Jay Indravadan Patel, Physical Therapist or Physiotherapist