Tenosynovitis or MTJ tear?

[Linh]

Dear Steve,

I got a challenging ankle today. Patient runs a lot but had no injury. Pain from just above Medial malleolus towards plantar hindfoot for 1 month. Tender when pressed. I found simple pockets of fluid surrounding the MTJ of TP, FDL and FHL. There is further tendon sheath fluid at the Knot of Henry where FDL and FHL crosses. Minimal hyperemia and thickening of tendons. I would assume that it there is any tear, the fluid should appear complex representing fibrin standing typical of organising haematoma (when the injury might happen within the one month period). But the radiologist said haematoma doesn’t have to appear like that. In your opinion, what is the likely diagnosis? How do we differentiate between tenosynovitis occurring near MTJ and a true MTJ tear?

Best regards,
Linh

[Stephen Bird]

Hi Linh,
This is an interesting observation.
The FHL tendon sheath communicates directly with the ankle joint much the same as the long head of biceps tendon communicates with the glenohumeral joint. This means that a small amount of fluid is really commonly seen in the proximal tendon sheath near the MTJ and also in the know of henry area of FHL in normal volunteers.
The tibias posterior tendon sheath also nearly always contains a small amount of fluid in normal volunteers near the insertion and commonly in the proximal tendon sheath although tib post does not communicate with the ankle joint.

So in these 2 tendons I don’t really associate a small amount of fluid with pathology, but rather as a normal finding.
BUT if the patient has clinical symptoms over the tendon and the sheath or if I see any wasculatity of either the tendon or the sheath I would consider this to be tenosynovitis.

FDL is a little different and I don’t really see fluid in this sheath very often.

For me to diagnose an MTJ tear I would need to see a muscle abnormality at the MTJ itself and remember there is an intra-muscular extension of these tendons and this is where these injuries occur. Fluid in the proximal sheath in my mind does not indicate that the pathology is in that part of the sheath as the fluid will move with posture and gravity / transducer pressure. Fluid in the sheath is just that and can be a normal finding as I described or associated with a tenosynovitis. I don’t really associate a sheath effusion with an MTJ tear.

In your case the tendon swelling and mild hyperaemia indicates tenosynovitis as the most likely diagnosis in my mind.

Steve

[Linh]

Thanks Steve. The tendon sheath is markedly distended with pockets of fluid so according to what you said, I’m now more confident I made the right call: tenosynovitis.

[Stephen Bird]

Yes, I think you are correct,

Steve

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