For every ankle MRI we order, it seems that a decent number of them are coming back with a split Tibialis Posterior tendon (also known as Posterior Tibialis tendon).
So it begs the question, is that the cause of pain or is a split Tibialis Posterior tendon a normal finding?
How common are traumatic Tibialis Posterior tendon tears?
It’s difficult to find much info on how often this tendon is injured in acute, or sudden, injuries.
One small study reported that around 1% of ankle sprains ended up with a Tibialis Posterior tendon tear.
How accurate are MRI and ultrasound at diagnosing split Tibialis Posterior tendons?
Interestingly, MRI and dynamic ultrasound have similar levels of accuracy for diagnosing Posterior Tibilais tendon splits.
MRI and dynamic (or in motion) ultrasounds will accurately diagnose a split Tibialis Posterior tendon in around 72% of cases.
Static (or stationary) ultrasound is still good but not quite as accurate.
Is inflammation around the Tibialis Posterior tendon a common MRI finding?
Short answer is yes – around 33% of ankle MRI will show some degree of inflammation around the Tibialis Posterior tendon.
More interesting though is the correlation to symptoms.
Of the 33% of MRIs with inflammation around the tendon, around 70% of those people don’t report any symptoms in the area.
So it appears that, while inflammation around Tibialis Posterior tendon is moderately common, it’s often not a cause of pain or symptoms.
Is a split Tibialis Posterior tendon normal?
From what we understand of anatomy and its variations, some people can be born with variations in tendon structure. But it’s not the majority of cases.
Others can develop splits in their tendon due to continuous loading, such as in marathon and distance runners.
That group is harder to quantify as there’s no studies on the topic.
The last group is the acute injuries – sudden tears of the Tibialis Posterior tendon.
As we reprted above, this group makes up less than 1% of all ankle sprains. So they’re not common either.
Does a split Tibialis Posterior tendon cause pain?
We know that inflammation around the tendon is common (33% of cases), yet symptoms associated with the inflammation are less common (pain reported in less than one third of cases.)
We also know that for a split tendon to be reacting, it will most commonly produce some sort of inflammatory response.
So a split tendon without inflammation is unlikely to be the cause of any symptoms.