If perfect knees existed, they would look like this image from an anatomy textbook. The three muscles of the vastus group are perfectly balanced, and rectus femoris isn’t too short nor too long. The result of this ideal musculature is that the patella (knee cap) is sitting in the centre of the joint – exactly where it is meant to be.
In real life, however, the patella will often sit off-centre. Although it’s not ideal, having an off-centre patella isn’t a real concern over the short-term (48-72 hours). Exercising quadriceps in the gym will pull the patella off-centre for a short time, so will sitting for an extended period of time, but if the patella stays off-centre, some more serious symptoms can present.
There are three directions that the patella can migrate: superiorly (upwards), medially (towards the middle of the leg), and laterally (towards the outside of the leg. The mechanism and symptoms of these migrations are all slightly different.
Superior (upward) movement.
This is when the patella sits higher than it should. It is a result of very tight quadriceps, usually from over-training. When the patella sits superior to the knee joint, you will lose range of motion through the knee. You can self-treat/prevent superior patella migration by doing a good quadriceps stretch.
Lateral (outward) movement.
This is when the patella sticks out towards the outside of the leg. It is a result of a very weak vastus medialis (VM) muscle – the small, tear-drop shaped muscle on the inside of your lower thigh. VMis a muscle that needs to be trained regularly and relatively specifically, so it's a commonly weak muscle. When VM is weak, it fails to pull the patella inwards, so it slips outwards. A lateral migration of the patella will cause pain, especially when walking down stairs. It can even cause arthritis if left untreated. To self-treat or prevent a lateral migration, try these exercises.
Medial (inward) movement.
This is rare amongst the general population, but relatively more common among athletes. It occurs when the VM isn’t weak, but too strong. It overpowers the other patella-stabilising muscles and pulls the knee cap medially. A medial migration has very similar symptoms to a lateral migration – pain and arthritis. To prevent medial migration, look at the exercises in THIS ARTICLE about VM tears.
For more information on plantar fasciitis, email me directly via the contact page. For specific information on an injury you have, or for treatment, contact one of my clinics directly. You can find that information here.
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Dr Mitch Clark