SINUS TARSI SYNDROME
The sinus tarsi syndrome is the term used for a conglomerate of pathological findings that result in pain and the lateral aspect of the mid foot.
The sinus tarsi is fibre osseous tunnel between the os calcis and talus.
It contains the talocalcaneal interosseous ligament and the cervical ligament (adjacent figure).
It lies at the anterior bound

The imaging findings depend on the underlying diagnosis. On MRI, the sinus contains a lot of fat and therefore classically returns high signal on sagital T1 weighted images. Loss of this fat signal indicates the presence of pathology and sinus tarsi syndrome. It is usually relatively easily to differentiate whether this is due to ganglion cyst or a synovial cyst formation.

SURAL NERVE
The sural nerve is formed from the medial sural cutaneous nerve which is a terminal branch of the tibial nerve and the lateral sural cutaneous nerve which is one of the terminal branches of the CPN.
These two nerves are connected by the sural communicating branch.
The sural nerve supplies sensation to the skin of the lateral foot and lateral lower ankle.
The sural nerve can be compressed, traumatised or inflamed.
Compressioncan be due to a mass lesion such as a ganglion or to trauma and vasculitis should be considered.
Occasionally a snapping syndrome with the Achilles tendon is encountered.

OTHER CONDITIONS

Lateral bundle plantar fasciitis
Stress fracture base of 5th MT
Os peroneum syndrome
Peroneus tertuus tendinopathy