Fourteen-year-old girl down the stairs knee pain may be growing pains, trauma, knee soft tissue injury, chondromalacia patella and other causes. 1. Growing pains: growing pains are children around the knee or calf anterior side pain, the site has no history of trauma, activities are normal, mostly due to the child’s activities are relatively large, the bone growth is relatively fast with the local muscle and tendon growth and development caused by incoordination. 2. trauma: fourteen-year-old female knee pain may be caused by knee collision, compression and other reasons, will show knee pain down the stairs. 3. Knee joint soft tissue injury: knee joint medial meniscus or collateral ligament and cruciate ligament injury, resulting in local knee joint soft tissue injury, there will also be knee pain, down the stairs with pain and other discomfort. 4. Chondromalacia patella: fourteen year old girl long time strenuous exercise, may cause the patella’s articular surface cartilage for a long time repeated friction, resulting in cartilage degeneration and damage after the pain, down the stairs in the process of the two articular surface contact area is getting bigger and bigger, friction force is bigger, the pain will be more obvious. Fourteen-year-old girl down the stairs knee pain causes more, it is recommended to timely medical treatment.