"Patellofemoral Pain" is another name for pain in the front of the knee, and its a very common reason for adolescent females (10 - 19 years old) to see an orthopedic doctor. It affects from 15-20% of females.
It remains unclear why young females experience these symptoms. There are two theories.
Theory One. Many believe that its due to overuse, when women are overtraining for high school sports. However, by that logic it should equally affect adolescent males.
Theory Two. Others believe that patellofemoral pain is caused by abnormal kinematics (knee motion). Terms such as abnormal "Patellar Tracking", abnormal "Patellar Angulation". Increased "tibial tuberosity–trochlear groove (TT-TG) distance", or increased "hip and knee abduction moments", and increased "lateral displacement of the patella", and "underdeveloped neuromuscular control patterns". These changes cause abnormal patellar tracking and increased contact forces within the knee causing pain.
A recent study directly showed a connection between abnormal kneecap motion and higher risk for patellofemoral pain.
Treatment. The primary goal is to treat this pain with physical therapy and muscle strengthening. These programs work in the vast majority of cases. Sometimes pain or instability persists. In these cases, advanced imaging like MRI or CT scan can be used to make measurements of the knee to determine if the structure of the knee is significantly abnormal. If it is, there are some surgery that can be performed to re-align the kneecap to improve its motion and reduce its pressure on the knee cartilage. These techniques are successful in the properly selected patients.
Adirim TA, Cheng TL. Overview of injuries in the young athlete. Sports Med. 2003;33(1):75-81. full article.
Barber Foss KD, Myer GD, Chen SS, Hewett TE. Expected prevalence from the differential diagnosis of anterior knee pain in adolescent female athletes during preparticipation screening. J Athl Train. 2012;47(5):519-524. full article.
Rathleff MS, Rathleff CR, Olesen JL, Rasmussen S, Roos EM. Is knee pain during adolescence a self-limiting condition? Prognosis of patellofemoral pain and other types of knee pain. Am J Sports Med. 2016;44(5):1165-1171. full article.
Thomee R, Renstrom P, Karlsson J, Grimby G. Patellofemoral pain syndrome in young women, I: a clinical analysis of alignment, pain parameters, common symptoms and functional activity level. Scand J Med Sci Sports. 1995;5(4):237-244. full article.
Balcarek P, Jung K, Frosch KH, Sturmer KM. Value of the tibial tuberosity-trochlear groove distance in patellar instability in the young athlete. Am J Sports Med. 2011;39(8):1756-1761. full article.full article
Dejour D, Le Coultre B. Osteotomies in patello-femoral instabilities. Sports Med Arthrosc. 2007;15(1):39-46. full article.