This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
A 17 year old athletic girl complains of anterior knee pain on climbing stairs and on getting up after prolonged sitting, likely diagnosis 
Select and explain. 
A. Blount's disease, B. Chondromalacia patella, C. Nail - patella syndrome, D. Bursitis
B: Chondromalacia patella
Answer: B: Chondromalacia patella 
Explanation: None