Overuse injuries are caused by repetitive action and are a separate classification as they are not an acute injury (like direct and indirect are) but a long term injury. They are much the same as indirect injuries because they are caused by internal forces. The distinct characteristic of an overuse injury is that it develops over time. This is usually because the athlete has not allowed enough time between performance for the body parts used in the repeated action to recover.
Overuse injuries begin as small injuries, often due to poor technique or constant repetition of particular movements, and develop into larger injuries because the athlete does not allow enough time to repair/recover from the smaller injury before it is re-injured. The small injuries produce scar tissue because the body does not have enough time to reproduce the actual body tissue. this often occurs in muscle tissue. This scar tissue then builds up because the body never gets a chance to repair and fix the tissue. This forms a weak area that is easily re-injured and often becomes a larger injury, even after recovery.
Overuse injuries include soft tissue injuries, such as tendonitis (e.g. tennis elbow) and hard tissue injuries, such as stress fractures.