The combination of these two abnormalities makes the VMO a less effective medial restraint.

The lateral retinaculum can be excessively tight. In this situation, the patella is laterally tilted (lateral [outside] side down) and or laterally displaced. There is a chicken and the egg situation with respect to whether a tight lateral retinaculum causes a tilted/displaced patella or whether a tilted/displaced patella leads to a tight lateral retinaculum.

The tibial tuberosity can be even more lateral to the midline than usual. This increases the quadriceps (Q) angle. In adolescence, this tuberosity can become enlarged and painful. When this happens, the patient is said to suffer from Osgood-Schlatter’s condition.

Parts of the lower extremity can exhibit torsional deformities, with one deformity "attempting" to compensate for another. For example, the hip can be anteverted. The femoral shaft can be internally rotated. The patella can follow the femur and point medially (the "squinting patella") or can remain in its normal position which then gives it a lateralized appearance ("grasshopper" appearance). A high-riding, lateralized patella can also give this appearance even without internal rotation of the femur. The tibia can exhibit torsion either proximally, distally or both. Proximally, torsion is usually external which leads to a lateralized tibial tuberosity. These types of complex, top to bottom rotational deformities have given rise to the term "miserable malalignment" – (referring to both the patient and the doctor!).

The patella can lie farther proximal than normal with respect to the trochlea. Thus the so-called height of the patella is greater than normal, a condition called patella alta. Conversely, the patella can be too far engaged into the trochlea (too close to the tibial plateau), a condition called patella infera or baja.

When viewed in a tangential fashion (as if looking at one’s own patella) the patella is horizontal when the leg is in neutral rotation. However, it is common in malalignment situations for the patella to be tilted, and, unless the patient has had surgery, tilt is always such that the medial [inner] side is elevated and the lateral [outside] side depressed (posterior).

When viewed in axial cross-section, the medial bony facet can be excessively small, there may be no separate medial and lateral bony facet, the patella may look like a hunter’s cap (as described by Wiberg) or a pebble - to name but a few abnormalities.

The trochlea can be shallow, the problem being either excessive thickness of the floor of the trochlea or insufficient height of one or both femoral condyles.

The nerves in the lateral retinaculum can exhibit fibrosis.

The entire extensor mechanism can be tight. In some cases this is mild and amenable to stretching. In other cases, the tightness is severe and can require a major surgical release (beginning at the hip). Such tightness can be caused by scarring down of the quadriceps (i.e. from trauma or injections) or can be congenital (in conjunction with a neuromuscular disease).

A plica can be become thickened and inflamed (it has been referred to as a "pseudo meniscus). As the knee flexes it can catch, pop and be painful.

A bursa can become inflamed in which case it fills with fluid and may be painful. This can occur seemingly spontaneously or can be the result of chronic irritation (i.e. after scrubbing the floor). It can fill with blood in cases of trauma, and it can become infected.