This pain can be due to many reasons like men8scal tear/ligament tear, generally due to any injury or wrong twisting movement. But if there is no history of any injury, it can be due to osteoarthritis, a condition in which joint space gets reduced, its due to old ageing factor. Pain increases when you get up from sitting, stair climbing, squatting, cold exposure, long standing and long walking.
Next Steps
Go to a physiotherapist.. Ultrasonic therapy +IFT +wax therapy +some strengthening exercises will be helpful for sure.
Health Tips
At home.. Rest +hot water fomentation +pain killer gel +no long standing /walking /stair climbing /travelling +no cold exposure +use knee cap +no low sitting.