However, pain is not always relieved
with rest, as this is somewhat dependent on the position of the
knee during rest. A common pattern with PFPS is for the person
to report an increase in pain if they sit for a long period with
the knee in flexion, such as after traveling for a lengthy trip
in a car or airplane, or sitting in a movie theater. Consequently,
this pain is sometimes referred to as a “positive movie
sign.” The pain will be felt immediately upon rising and
will generally dissipate a few minutes after the person walks
around. PFPS may affect one or both knees.
Sensations of grinding may also be
reported when the knee is moved through flexion and extension.
Pain is usually worse when flexion and extension movements are
done against resistance or in a weight-bearing position.
For example, squatting would be more
painful than sitting on the edge of the treatment table and extending
the knee. Both motions move the knee through flexion and extension,
but in the first case there is resistance to the extensor mechanism
that would aggravate the PFPS pain. Unless the condition is in
a very advanced stage, pain is not common with any passive movements
because there is not enough stress on the involved tissues.
There are no outwardly visible signs
of PFPS, though certain biomechanical or postural distortions
can play a major role in this condition. Observing their presence
is a helpful indicator. Especially important is the presence of
genu valgum ("knock knees") or a large Q angle. These
postural distortions will increase the tendency for lateral tracking
of the patella because the angle of pull of the quadriceps muscle
group is altered.
As a result of pain and dysfunction
some muscles, such as the quadriceps, will atrophy rapidly. If
there is a difference between the symptomatic and non-symptomatic
sides, it may show up as a difference in muscle circumference,
indicating muscle atrophy. While this does not specifically identify
that PFPS is the cause, it does indicate that something is causing
a degree of quadriceps atrophy and PFPS may play a role in it.
indicator that may be helpful in identifying the knee-extensor-system
pathology of PFPS is the degree of medial and lateral glide of
the patella. The patella should be able to freely move in these
directions. However, it should not glide too much (see Figure
4). PFPS can be the result of either too much glide or too little.
Somewhere around half its width appears to be the proper amount
of side-to-side movement in the patella.
In some cases it will be difficult
to reproduce the pain of PFPS with palpation and in other cases
it can be easier. This is primarily because the tissue that is
producing the pain can vary. For example, if the pain is primarily
coming from irritation of the sub-chondral bone on the underside
of the patella, it is not likely that light or moderate palpation
anywhere around the knee will reproduce that discomfort. However,
if the patella is pressed against the femoral condyles with greater
pressure, the pain may be felt in this instance.
on the other hand, the pain is arising from more superficial tissues
around the knee, such as the quadriceps retinaculum, it may be
easy to reproduce the characteristic pain the client has been
reporting by palpating this region. It is likely that pain will
be exaggerated if these tissues are stretched, so the palpation
should be performed with the knee in flexion.