Tricky one Mike,
There is no doubt there is some peroneal tenosynovitis,
But this never happens without an underlying pathological cause!
Most commonly peroneus brevis compression from longus at the medial malleolus and progressing to a longitudinal split.
Second most common: peroneal tubercle syndrome stenosing tenosynovitis of peroneus longus. This happens a little further distal at the level of the peroneal tubercle.
Third option: Os peroneum which is an accessory tubercle in the peroneus longus at the high compression point as the tendon passes around the cuboid before passing into the plantar foot.
In your case there is a bone that is not standard anatomical and it appears to be in the peroneus longus tendon.
The os peroneum is certainly in peroneus longus, however this ossicle looks like it is more proximal than I would normally expect.
Os peroneum is typically at the level that the peroneus longus wraps around the cuboid,
This ossicle looks more proximal, closer to where I expect the peroneal tubercle to be,
What level was this ossicle at?
The ossicle is also somewhat irregular,
I have no doubt this ossicle is a culprit!
From the images provided I would suggest there is an irregular os peroneum setting up a localised tendinosis and associated peroneal tenosynovitis.
I am uncertain as to the exact anatomical location of the ossicle and am wondering if it is a little more proximal to the usual location (at the “cuboid corner”).
This raises questions about the distal peroneus longus insertion.
It also raises the question as to if the peroneal tubercle is normal
The lateral band of the plantar fascia insertion onto the base of 5th MT is really nicely imaged and normal.
Let’s continue the conversation.
Steve.