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.
People with neurogenic hypertension respond poorly to treatment with diuretics as the underlying cause of their hypertension is not addressed.Pheochromocytoma – a tumor which results in an excessive secretion of norepinephrine and epinephrine which promotes vasoconstriction
Hyperaldosteronism (Conns syndrome)   – idiopathic hyperaldosteronism, liddles syndrome (also called pseudoaldosteronism), glucocorticoid remediable aldosteronism
Cushings syndrome – an excessive secretion of glucocorticoids causes the hypertension
Hyperparathyroidism
Acromegaly
Hyperthyroidism
Hypothyroidism

Adrenal
A variety of adrenal cortical abnormalities can cause hypertension, In primary aldosteronism there is a clear relationship between the aldosterone-induced sodium retention and the hypertension.Congenital adrenal hyperplasia, a group of autosomal recessive disorders of the enzymes responsible for steroid hormone production, can lead to secondary hypertension by creating atypically high levels of mineralocorticoid steroid hormones. These mineralocorticoids cross-react with the aldosterone receptor, activating it and raising blood pressure. 17 alpha-hydroxylase deficiency causes an inability to produce cortisol. Instead, extremely high levels of the precursor hormone corticosterone are produced, some of which is converted to 11-Deoxycorticosterone (DOC), a potent mineralocorticoid not normally clinically important in humans. DOC has blood-pressure raising effects similar to aldosterone, and abnormally high levels result in hypokalemic hypertension. 11β-hydroxylase deficiency, aka apparent mineralocorticoid excess syndrome, involves a defect in the gene for 11β-hydroxysteroid dehydrogenase, an enzyme that normally inactivates circulating cortisol to the less-active metabolite cortisone. At high concentrations cortisol can cross-react and activate the mineralocorticoid receptor, leading to aldosterone-like effects in the kidney, causing hypertension.