 My name is Dr. Ankit Shah and I shall be talking about ultrasound anatomy of the ankle and the scanning technique. The number of tendons and ligaments criss-crossing the ankle joint can sound quite intimidating when you have just started doing MSK ultrasound. A systematic ultrasound examination of the various structures can be easily performed by dividing the ankle into four quadrants. That is the anterior, medial, posterior and lateral. Division of the ankle structures into the various quadrants makes your life much more simpler. So that when you know that you have to assess the anterior telophibular ligament, you know that all you've got to do is assess the anterior quadrant. Or when there's pain along the lateral aspect of the ankle, you need to know that yes, I'm going to assess the peroneal tendons and so on. So let's begin with the posterior ankle wherein we'll be assessing the Achilles tendon and the plantar fascia. The plantar fascia is not technically a part of the ankle joint. However, there are quite a few referrals for assessment of the plantar fascia. Hence, we've included this in the posterior quadrant. The Achilles tendon is a long, strong and a broad tendon which is formed by the tricepsurae. That is, the medial and lateral heads of the gastronomies and the soleus. On cross-section in the peri-insertional fibres of the Achilles tendon, we see a number of structures, which is the peri-insertional fibres of the Achilles tendon, the retrocalcaneal bursa located between the tendon and the calcaneum, the Kegos fat pad, a potential bursa between the tendon and the subcutaneous fat, which is also known as a pre-Achilles bursa. On the transverse view or on the short axis, the Achilles tendon is seen as an oval or a rheniform structure with a typical brushed border kind of an appearance. The normal tendon does not have a tendon sheath. However, it is surrounded by a connective tissue, which is known as paratinon. The paratinon would appear as a thickened or a hypoechoic halo when there is tendonosis or when there's a tendon tear. And it generally consists of blood vessels which supply nutrients to the tendon. On the long axis, we see the Achilles tendon typically as a fibrillary structure as it goes and attaches over the calcaneum. We see over here that there is a hypoechoic area in a segment of the tendon. This is caused due to anisotropy. So these collagen fibres as they go and attach over the calcaneum, they curve anteriorly. And because of this anterior turn, there is an artifact which is known as anisotropy. You should be aware of this before labeling the tendon as insertional tendonosis. Now, anterior to the tendon, what we see is a hypoechoic structure, a comma-shaped hypoechoic structure nestled between the tendon and the calcaneum. This is known as a retrocalcaneal bursa. And just above this fat pad, this echogenic fat pad, this is known as a kega's fat pad. Now, some amount of fluid is accepted within the retrocalcaneal bursa. In the presence of appropriate symptoms, if there's fluid more than 2 mm in thickness, then this finding would be significant. Approximately, we assess the Achilles tendon at the attachment of the soleus or the myotendonus junction of the soleus, because most of your athletic injuries are going to happen at this site. When we look at the Achilles tendon, it's a broad area to be scanned. Hence, I would encourage the students and the people who do regular musculoskeletal ultrasound to start doing panoramic or extended field of view sections. Because the more the anatomy you take in, the better is the pathology appreciated and everybody gets a better perspective. Now, in this section, just in one view, we see the calcaneum, the insertion fibres of the Achilles tendon, the main tendon, as well as the myotendonus junction. So, we look at the tendon, the three broad segments of the tendon. So, one would be the periinsertion area where we have most of your anthocytus and the calcific tendonosis happening. There's a second area. This is known as a critical zone. This zone typically is 2 to 6 centimeters proximal to the Achilles tendon. This is where most of your tendonosis or your degenerative tears are going to occur. And, proximally, at the myoponeurotic junction, you'll have the athletic injuries. So, with the Achilles tendon, we move on to plantafesia. The plantafesia is not just a broad fascia. It typically has three cords. That is the central cord, which is the main component, the lateral cord, and the medial cord. The medial cord is not clinically that relevant. However, most of your plantafesitis is going to involve the central cord. When we put a probe along the long axis of the plantafesia, we see a typical fibrillary structure which goes and attaches over the smooth cortex of the calcaneum. We measure the plantafesia thickness just as it exits the posterior medial tubercle. In the presence of appropriate symptoms, any thickness more than 4 millimeters is considered significant. Now, on this extended field of view, we see that the plantafesia is seen traversing from the posterior aspect of the foot to the anterior aspect. As it goes anteriorly, it becomes, from a deeper structure, it becomes much more superficially as we move towards the metatarsal heads. After evaluating the plantafesia on the long axis, we assess the plantafesia and the short axis as well so that we don't miss out on areas of focal plantafesitis. We are able to classify the exact location of the plantafesia. Is it involving the medial cord or the lateral cord? With that, we are done with the evaluation of the posterior ankle.