Introduction to biomechanics


What Is Anterior Knee Pain?

Knee pain has can be dressed up in manyOne of the main culprits behind the altered
different guises. Whatever someone decides topositioning of the patella is a weakness in
call it, all we need to know is that itvastus medialis obliqus (VMO). This muscle
usually occurs on the front of the knee andattaches medially (to the inside) on the
it  hurts!patella with weakness here allowing the
patella to drift laterally (outwards). This
The pain is normally associated with running,muscle is the first of the muscles to waste
walking down hills/stairs, or sitting with afollowing injury and lack of use of the
bent knee for long periods of time. This isquadriceps muscles. The quadriceps muscles
due to an alteration in the biomechanics ofcan start wasting within 24 hours of non-use!
the knee which is usually caused by anTreatment may therefore consist of
imbalance  in  the  soft  tissue  structures.strengthening of the VMO muscle to alter the
pull of the quadriceps on the patella thus
The pain within the knee joint usuallycorrecting  its  position.
increases when the quadriceps muscles work
eccentrically (meaning the muscles working asLikewise shortening of vastus lateralis which
they get lengthened). This exerts a largeattached to the lateral aspect of the patella
force through the patella (knee cap) when themay also result in an outward pull on the
muscles are used this way. The large forcepatella again affecting the Q-angle.
presses the patella against the femoralTreatment here would consist of heat,
groove, which if not located correctly causesstretching and massage to normalise the
pain.length of the muscle. In extreme cases
surgery may be required to 'release' the
Mal-tracking of the patella within themuscle to allow the patella to re-position
femoral groove is the most common cause ofitself  correctly.
anterior knee pain. This is like a train
being driven off its rails which will lead toOther causes of anterior knee pain from the
a bumpy and uncomfortable ride! An imbalancepatella-femoral  joint  include
in the pull of the quadriceps muscles (vastus
medialis, vastus lateralis, vastus" Tightness in certain structures (e.g. calf
intermedius and rectus femoris) which attachand  hamstring  muscles).
to  the  patella  can  alter  its  position.
"  Altered  hip,  knee  or  foot  posture.
The angle of pull of the quadriceps muscle
through the patella is known as the Q-angle." Anatomic variations such as a shallow
The Q-angle is determined by drawing a linepatella-femoral  groove.
from the ASIS (bony point on the front of the
pelvis) to the midpoint of the patella with aIf knee pain is left untreated the articular
second line being drawn from the centre ofsurfaces of the patella-femoral joint may, in
the tibial tubercle (flat piece of bone belowsome cases, become affected and worn,
the knee cap) to the middle of the patella.exacerbating  the  problem.
The point where these two lines cross is
known as the Q-angle which should be 13ÚThese are just a couple of examples of causes
in males and 18Ú in females. Anythingof anterior knee pain. To have your specific
outside these ranges could be the causecondition diagnosed correctly it is advised
behind knee pain. Note when performing thesethat you seek medical advice from a
tests  the  leg  should  be  relaxed.professionally qualified practitioner.



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