Patellofemoral pain syndrome (PFPS)[2]
PFPS is a diagnosis of exclusion and is defined as pain behind or around the patella. It is synonymous with the term retro-patellar pain and has in the past been referred to as chondromalacia patellae. It is caused by compressive forces in the patellofemoral joint (PFJ). PFPS is very common. Symptoms are usually provoked by climbing or descending stairs, squatting and sitting with flexed knees for long periods of time.