#47659
Stephen Bird
Keymaster

Hi Sandy,

I find the concept of “sinus tarsi syndrome” a little confusing.

But this is my view of it.

Sinus tarsi syndrome as I see it is pain arising in the sinus tarsi so it is actually on the other side of the foot to the tib post tendon.

The technique I use is to follow the peroneal tendons down from the lateral malleolus.
I identify the superior peroneal retinaculum, keep following them in short axis distally and you will see the CFL passing beneath them.

At this point look slightly anterior to th e peroneus brevis tendon and you will see a “crack in the bone” which is the joint between the calcaneum (posteriorly) and the talus (anteriorly).

Once you see this joint you have found the lateral aspect of the posterior subtler joint. I assess this joint for arthritic changes like osteophyte formation and also effusion / synovitis.

Then keep moving the transducer in the short axis of peroneus brevis slightly more distally and the talus will disappear from view while the calcaneum will remain. The area where the talus was is replaced by a triangle of fat which is the sinus tarsi. You may want to drop your frequency a little as it is a deep structure filled with fat that is attentive.

If I see a monoloculated fluid puddle that is compressible and it sits adjacent to the calcaneum within the sinus tarsi this represents a posterior subtler joint effusion. A small puddle is physiological.
If I see a multiloculated non compressible fluid collection this is a ganglion and I can’t really ever determine which articulation it arises from, but it will be arising from the floor of the sinus tarsi.
If I see an oval shaped fluid collection on the talar side of the sinus tarsi deep to the extensor digitorum apparatus this is a Gruberi Bursa. A bit of fluid in this bursa is very common and often asymptomatic, however like all bursae it can become inflamed and I comment on it if there is point tenderness and vascularity with the Doppler. An effusion in the dorsal talonavicular joint can also mimic the Gruberi bursa.

A common thing I see is generalised hypervascularity of the sinus tarsi fat with a posterior subtler joint effusion also being present. When you look more closely you can appreciate it is a posterior subtler joint synovitis event that has extended conveniently into the sinus tarsi.
You can use a medial and also a posterior approach to the subtalar joint and you will get further confirmation of subtler joint synovitis.

There is also several reflections of the extensor retinaculum apparatus that reflect through the sinus tarsi fat. The 2 easiest bands to see monographically wrap around the extensor digitorum longus tendons then pass through the sinus tarsi to attach on the calcaneum. Once you appreciate that these structures exist you can go looking for them in people who have had ankle / foot trauma and have pain in the sinus tarsi and I have a nice collection now of cases where these bands of the extensor retinaculum have been damaged.

So as you can see I don’t have a nice simple definition of sinus tarsi syndrome but rather I search for this broad constellation of findings.

I am certain this is an area most of us can do better. There has been some recent publication from an Italian group who have described the anatomy in wonderful detail. It is COMPLICATED !!

I am happy to share the reference if you are interested.

Steve.

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