Patellar instability - subluxation or dislocation - can be congenital or acquired. A congenital condition is a condition someone is born with. An acquired condition is a condition that comes on due to injury or incorrect surgery.

Previous blogs have discussed the patella as a sesamoid bone and on the patella as part of the extensor mechanism.

I mentioned there that the patella is a bone that exists within the tendon of the quadriceps muscle, and that the muscle is tethered above to the hip and bits of it to the upper femur, and that it is tethered below to the tibia bone.

There are quite a lot of medical words that need to be absorbed before one can confidently talk about the patella and its problems, and the extensor mechanism falls into that group.

The patella (kneecap) is a 'sesamoid bone'. A sesamoid bone is a bone that develops in a muscle tendon, rather than being attached by ligaments to another bone. The tendon in which the patella develops is the tendon of the quadriceps muscle, the big muscle that makes up the bulk of your 'lap'.

For those bulletin board members who have had articular cartilage repair and who have participated in the survey posted up recently by Karen Hambly, I am sure you will be interested to know that the results were published in a major medical journal. You can get the details here.

This very sophisticated discussion on the bulletin board will be of interest to readers who want to know what difference there is in outcome between ACI and Microfracture.