The pain has steadily worsened, so his parents take him to the doctor. While Brian has been pounding up and down the soccer field for the past 12 months, the growth cartilage at the bottom of his thighbone has been grinding against the top of the shinbone, causing a stress fracture of the joint's surface cartilage. Teenager's knee is an overuse injury. Unlike acute injuries, which are caused by a single, severe trauma, overuse injuries result from repetitive microtrauma to bones or joints caused by doing the same activity whether it's running, throwing a baseball, or flexing the lower back over and over again. Overuse injuries, such as teenager's knee, Little League elbow, swimmer's shoulder, and gymnast's back, are becoming much more common than in the past.
Children are especially vulnerable to overuse injuries because their bones are growing.
Parents and coaches should be on the lookout for a pattern of symptoms that typically occurs as an overuse injury develops. First, a child will have sore muscles for a few hours after a workout. Next, muscle pain will persist into the following morning. Later, a child will have pain toward the end of a workout, and then throughout the entire workout. Finally, the pain will occur with routine motions.