The best way to prevent sports injuries is proper training and conditioning. Sometimes I get a pain in the side of my knee, the outside, when I'm running. Someone told me it was my IT Band. The IT band is muscle that runs down from the hip to the knee. It helps in bending the knee.
Some people get some inflammation where the IT bank attaches to the bone at the knee.
This more commonly occurs with runners. The most common age-related hip injuries are fractures. You can also have bursitis around the hip joint and that can be related to sporting activities because this is usually an overuse problem. Anytime you have an injury to one joint that can affect other joints. If you are unable to fully extend your knee while you are walking, you are often unable to fully extend your hip while you are walking as well.