When kneecap (patellar) pain is first experienced, there may have been no injury and the patella itself may have no structural abnormality.

Pain may initially be vague in nature and experienced behind or around the front of the kneecap. A patient may rub the whole front of the knee rather than using the index finger to point to a particular spot.

Together with this pain, patients may complain that there is discomfort on descending or ascending stairs, or walking downhill or on uneven surfaces. The knee may become stiff and uncomfortable after sitting for a long time. There may be crunchy noises or a grating sensation (patellar crepitus) on bending and straightening the knees.

When this set of symptoms is associated with the patella being out of alignment or tracking badly in its underlying groove, then this is known as the 'patellofemoral syndrome'. Note that a syndrome is a set of symptoms that tend to occur together rather than an actual diagnosis of the cause of the symptoms.

extensor mechanism

The strain on the patella may be the result of an abnormality anywhere in the chain of structures influencing the alignment or tracking of the patella - from the hip, though the femur bone, the tibia bone and down to the feet - and including the quadriceps muscle (of which a part, the rectus femoris, is shown in the illustration) and its attachment to the tibial tubercle.

A full evaluation of patellar pain should include observation of the gait, the standing posture, the feet, the tibia and femur bones, the patella itself and the groove in which it glides, as well as the hip and lower back.

The problems that one might find causing or aggravating PFS include -

Hip imbalance

Imbalance of adductors and abductors, weakness of external rotators.

Tight iliotibial band (ITB)

The fibrous band that runs the full length of the upper leg from hip to knee may become tight and contribute to patellofemoral pain.

Quads weakness

Weak quadriceps muscles, especially the oblique part of the vastus medialis head known as the VMO (vastus medialis obliquus), may allow the patella to align to the lateral side. The VMO plays a big role in tightening the medial retinaculum and keeping the patella aligned in the centre of the underlying groove.

Quads/hamstrings imbalance

It has been found in patients with PFS that the hamstrings are often weak in relation to the quadriceps muscle. A balance in quads and hams contributes to patellar stability.

Abnormalities of the arch of the foot

Arch abnormalities, especially flat-footedness, can cause an alteration in the alignment of the whole limb with malalignment and maltracking of the kneecap.

Tight calf muscles

Tight calf muscles can cause a compensatory rolling-in of the foot, with consequent alteration of limb alignment and stress on the kneecap.