Injury can affect any of the
ligaments, bursae, or tendons surrounding the
knee joint. Injury can also affect the ligaments, cartilage, menisci (plural for meniscus), and bones forming the joint. The complexity of the design of the knee joint and the fact that it is an active weight-bearing joint are factors in making the knee one of the most commonly injured joints. It's not necessarily arthritis; you're 23, you're young. I'm sure you do activities such as sports.