Hi, this is Dr Mathur orthopaedic surgeon from Fortis C Doc Hospital, New Delhi. Welcome to practo. The part of bone that you are refering to serves as the attachment of a ligament originating from the knee cap. That part of the ligament is stretched while straighting the knee. Pain at that point can arise due to partial tear of the ligament followed by inadequate rest given to the ligament to heal making it a chronic pain or inflamed attachment of the ligament. Some physiotherapy like ultrasonic therapy and IFT along with use of a knee brace for 3 weeks can help. Nsaid drugs can help decrease the inflammation as well. Also get your serum
uric acid (blood test) fasting and xray of the knee AP and lateral views and revert back with reports.