Individuals with PFP may be exhibit higher pain level and lower function.Magnetic resonance imaging rarely can give useful information for managing patellofemoral pain syndrome and treatment should focus on an appropriate rehabilitation program including correcting strength and flexibility concerns. In the uncommon cases where a patient has mechanical symptoms like a locked knee, knee effusion, or failure to improve following physical therapy, then an MRI may give more insight into diagnosis and treatment. Classification
PFPS is one of a handful of conditions sometimes referred to as runners knee; the other conditions being chondromalacia patellae, iliotibial band syndrome, and plica syndrome. Chondromalacia patellae is a term sometimes used synonymously with PFPS. However, there is general consensus that PFPS applies only to individuals without cartilage damage, thereby distinguishing it from chondromalacia patellae, a condition with softening of the patellar articular cartilage. Despite this distinction, the diagnosis of PFPS is typically made based only on the history and physical examination rather than on the results of any medical imaging. Therefore, it is unknown whether most persons with a diagnosis of PFPS have cartilage damage or not, making the difference between PFPS and chondromalacia theoretical rather than practical. It is thought that only some individuals with anterior knee pain will have true chondromalacia patellae. Differential diagnosis
The diagnosis of patellofemoral pain syndrome is made by ruling out patellar tendinitis, prepatellar bursitis, plica syndrome, Sinding-Larsen and Johansson syndrome, and Osgood–Schlatter disease. Currently, there is not a gold standard assessment to diagnose PFPS. Treatment
A variety of treatments for patellofemoral pain syndrome are available.
Pain is usually initiated when weight is put on the knee extensor mechanism, such as when ascending or descending stairs or slopes, squatting, kneeling, cycling, or running. Pain during prolonged sitting is sometimes termed the "movie sign" or "theatre sign" because individuals might experience pain while sitting to watch a film or similar activity. The pain is typically aching and occasionally sharp. Pain may be exacerbated by activities. The knee joint may exhibit noises such as clicking. However, this has no relation to pain and function. Giving-way of the knee may be reported. Reduced knee flexion may be experienced during activities. Causes
In most patients with PFPS an examination of their history will highlight a precipitating event that caused the injury. Changes in activity patterns such as excessive increases in running mileage, repetitions such as running up steps and the addition of strength exercises that affect the patellofemoral joint are commonly associated with symptom onset. Excessively worn or poorly fitted footwear may be a contributing factor. To prevent recurrence the causal behaviour should be identified and managed correctly.The medical cause of PFPS is thought to be increased pressure on the patellofemoral joint. There are several theorized mechanisms relating to how this increased pressure occurs:

Increased levels of physical activity
Malalignment of the patella as it moves through the femoral groove
Quadriceps muscle imbalance
Tight anatomical structures, e.g. retinaculum or iliotibial band.Causes can also be a result of excessive genu valgum and the above-mentioned repetitive motions leading to abnormal lateral patellar tracking.