The knee joint is surrounded by fluid-crammed sacs named bursae, which serve as gliding surfaces that reduce friction on the tendons. Underneath the kneecap, There exists a huge tendon (patellar tendon) which attaches for the front in the tibia bone. Weakened bone and cartilage from your thighbone, shinbone and kneecap https://www.theorthopaedicandpainpractice.com/what-should-i-do-if-i-have-a-collateral-ligament-injury-of-the-knee/?_gl=1*xbbxlb*_up*MQ..&gclid=Cj0KCQjwkt6aBhDKARIsAAyeLJ2krYJSOuy5mZksrNqH-VDjQwW1ScD49yD8BUWysDG6u6bJPCSbXVUaAuCPEALw_wcB