 Coming to the medial quadrant of the ankle, we have the tibialis posterior and the flexor digitorum longus tendons, flexor helicis longus tendon and the posterior joint recess, the tarsal tunnel and the tibial nerve and the deltoid ligament. Before we begin with evaluation of the medial quadrant structures, it's a great idea to revise the Auschwitz anatomy, out of which the most important structures are going to be the medial malleolus, the navicularis or the navicular bone and the posterior tubercle of the talus. Now, this is a volume rendered image where we see the location of the tibialis posterior tendon. Just adjacent to that, we have the flexor digitorum longus tendon and a little bit more posteriorly, we have the flexor helicis longus tendon as it passes between the two tubercles of the talus. So, that's the tibialis posterior, the flexor digitorum longus and the flexor helicis longus. So, this is a gross dissection where we see the location of the tibialis posterior tendon which is labeled number five as it passes over the deltoid ligament. Just look at the anatomy or the relationship of the tibialis posterior with regards to the deltoid ligament. It rests on the deltoid ligament as if it's on a hammock. The tibialis posterior on the short axis is seen as an ecogenic structure with a brush border kind of an appearance. It just looks like any other tendon in the body and right adjacent to that is a flexor digitorum longus tendon. Now, if we look at both of them, the tibialis posterior is almost twice the size of the FDL tendon and when we are scanning the tendon, we scan the tendon all the way from the supramalliolar segment, the retromalliolar and the inframalliolar segment as the tendon goes and attaches over the navicularis. On the short axis and then from the maliolar segment, just below the tibialis posterior, we see a broad chord like structure. This is the tough spring ligament. So, when we are evaluating the tibialis posterior dysfunction, it's important to assess the spring ligament as well since after the failure of the tibialis posterior tendon, it's the spring ligament which gives way and contributes to the loss of the or rather would be involved when there's loss of the medial arch of the foot. On the long axis, then the tibialis posterior is seen as a tendon with a fibrillary pattern. It goes from the supramalliolar, retromalliolar and the inframalliolar segment till it reaches the navicularis. Now, one more thing that you need to know or maybe it's just that the tendon sheath of the tibialis posterior extends just one to two centimeters distal to the medial malleolus. So, after that one to two centimeters, there is actually no tendon sheath. So, if the periinsertional, if you see some fluid in the periinsertional fibers of the tibialis posterior, it's more likely to represent paratendinosis or panoractendinitis rather than true tinoxinovitis. The flexor helicis longus as it passes through the posterior between the two tubercles of the talus actually has some fluid over here. Now, we need to know that some amount of fluid in the flexor helicis longest tendon sheath has a normal finding because the tendon sheath actually communicates with the joint space. Hence, before you call some fluid within the FHL tendon sheath as tinoxinovitis, make sure that it is actually not an anatomical variant. The tassel tunnel is a fibroseous tunnel just like any other fibroseous tunnel in the body which consists of the tibialis posterior tendon, the flexor digitorum longus tendon, the posterior tibial artery, vein, the nerve and the flexor helicis longest tendon. You know, we used to remember this as the Tom Dick and a very nervous Harry. So, this tunnel is formed by the flexor retinaculum which spans between the medial malleolus and the calcaneum. So, on the short axis, this is the flexor retinaculum and these are the various structures which are seen. If there is any ganglion cyst or if there is a varix or if there is any soft tissue lesion, this may result in compression of the posterior tibial nerve and result in neurogenic symptoms. The deltoid ligament is made up of the spring ligament complex that will be an avicular ligament, tibial spring ligament, tibial calcaneal ligament and the tibiotala ligament. Now, all these structures are really nice to discuss, you know, theoretically. However, when we look at the deltoid ligament as a gross structure, it may or may not be able to identify the various components that we've already described over here. Hence, as a sonologist, maybe you know if you have to include this in your report, maybe you can report it as if there's a full-thickness tear or a partial tear and your job is done. You know, there are quite a few variations and you may or may not be able to identify all the components of the deltoid ligament complex. So, we put our proximal end of the probe over the medial malleolus and we swing the probe from posterior to anterior using the medial malleolus as a fulcrum, which, you know, the movement of the probe is like that of a fan. So, posteriorly, we see the tibiotala ligament, we see the tibiotalcaneal ligament, the tibiotal spring component and anterior is the tibiotal navicular ligament. The spring ligament proper is seen as a broad echogenic structure and the tibialis posterior tendon lies just over it. So, if you look at the position of the probe, it's almost parallel to the sole of the foot. So, when we're looking at the tibialis posterior dysfunction after evaluating the tibialis posterior tendon, it's a good idea to look for spring ligament tears as well. Now, when we're doing MR, we can see all the components of the spring ligament. However, on ultrasounds, all we can see is a superior medial component, which is the most important one.