What Is Anterior Knee Pain?

Knee pain has can be dressed up in many different guises. Whatever someone decides to call it, all we need to know is that it usually occurs on the front of the knee and it hurts!

The pain is normally associated with running, walking down hills/stairs, or sitting with a bent knee for long periods of time. This is due to an alteration in the biomechanics of the knee which is usually caused by an imbalance in the soft tissue structures.

The pain within the knee joint usually increases when the quadriceps muscles work eccentrically (meaning the muscles working as they get lengthened). This exerts a large force through the patella (knee cap) when the muscles are used this way. The large force presses the patella against the femoral groove, which if not located correctly causes pain.

Mal-tracking of the patella within the femoral groove is the most common cause of anterior knee pain. This is like a train being driven off its rails which will lead to a bumpy and uncomfortable ride! An imbalance in the pull of the quadriceps muscles (vastus medialis, vastus lateralis, vastus intermedius and rectus femoris) which attach to the patella can alter its position.

The angle of pull of the quadriceps muscle through the patella is known as the Q-angle. The Q-angle is determined by drawing a line from the ASIS (bony point on the front of the pelvis) to the midpoint of the patella with a second line being drawn from the centre of the tibial tubercle (flat piece of bone below the knee cap) to the middle of the patella. The point where these two lines cross is known as the Q-angle which should be 13Ú in males and 18Ú in females. Anything outside these ranges could be the cause behind knee pain. Note when performing these tests the leg should be relaxed.

One of the main culprits behind the altered positioning of the patella is a weakness in vastus medialis obliqus (VMO). This muscle attaches medially (to the inside) on the patella with weakness here allowing the patella to drift laterally (outwards). This muscle is the first of the muscles to waste following injury and lack of use of the quadriceps muscles. The quadriceps muscles can start wasting within 24 hours of non-use! Treatment may therefore consist of strengthening of the VMO muscle to alter the pull of the quadriceps on the patella thus correcting its position.

Likewise shortening of vastus lateralis which attached to the lateral aspect of the patella may also result in an outward pull on the patella again affecting the Q-angle. Treatment here would consist of heat, stretching and massage to normalise the length of the muscle. In extreme cases surgery may be required to 'release' the muscle to allow the patella to re-position itself correctly.

Other causes of anterior knee pain from the patella-femoral joint include

" Tightness in certain structures (e.g. calf and hamstring muscles).

" Altered hip, knee or foot posture.

" Anatomic variations such as a shallow patella-femoral groove.

If knee pain is left untreated the articular surfaces of the patella-femoral joint may, in some cases, become affected and worn, exacerbating the problem.

These are just a couple of examples of causes of anterior knee pain. To have your specific condition diagnosed correctly it is advised that you seek medical advice from a professionally qualified practitioner.