Stephen Bird

Hi David,

Great question.

Tib post gets tenosynovitis for many reasons.

It is often from overloading stress of the tendon, having to work too hard holding up the longitudinal medial arch.

The difficulty in the arch support can be from diabetes, smoking, obesity, post menopause changes in collagen support, static stabilizer insufficiency (plantar fascia, deltoid lig, spring lig) and most often biomechanical issues.

So it is complicated.

The scenario is tib post overload leading to tendinosis or a longitudinal split tear and this degenerative change in the tendon leads to an inflammatory response from the synovial entheseal complex in the form of tib post tenosynovitis.

There is another scenario where there is a type 2 os tibiale externum accessory ossicle present and the synchondrosis bonding the ossicle to the navicular becomes a site of traction stress again setting up a localized inflammatory response. In these cases the inflammatory response often extends to the navicular -medial cuneiform ligament apparatus.

In both cases the inflammation often extends into the deltoid ligament complex and the spring ligament as well.

I think of it like a fire burning and if you are the neighboring property, you get involved with smoke or heat damage. It is interesting to see how inflammation goes from structure to adjacent structure in the MSK system.

So you need to think of tib post tenosynovitis as a symptom, not a cause.

With the exception of rheumatoid patients the tenosynovitis is not a primary pathology.

The primary pathology is either degenerative changes in the tib post tendon or synchondrosis issues as described and the tenosynovitis is a secondary response from the SEC (Synovial entheseal complex).

As for other structures, once the tib post is failing then you have an inadequate dynamic stabiliser of the longitudinal arch and this leads to overload of the static stabilisers. The static stabilisers include the spring ligament, the deltoid ligament complex and the plantar fascia. Also the tib ant tendon may also become overloaded and hence it is worth including all of these structures in your assessment.

We have had a private discussion about weather a Tib Post to FDL ratio might be of use when trying to decide if the tib post is swollen.

It might have some merit in investigating.

How you measure the tib post will make a difference as it is oval shaped, while FDL is round.

Shortest axial axis to shortest axial axis could produce a useful ratio.

You could also try cross sectional area to cross sectional area and come up with a ratio.

It would be a good research project for someone!

Have a great day up there Dave,


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