 Hello everyone, I am Dr. Chaitali Parek and it's a privilege to be a part of the Indian Radiologist group. After my Masters in Radiology, I have done a fellowship in musculoskeletal intervention radiology at the well-renowned sportsmen hospital and innovation imaging under the aegis of Dr. Aditya Dakhthari and Dr. Malini Lavande for almost two years. Currently, I am the co-founder of MSK Insight and practicing as a musculoskeletal intervention radiologist at the pulse chain of diagnostic centres across Mumbai and New Tech Diagnostic Centre Kalyan. And we'll be discussing on the MRI anatomy of the ankle joint. In this short session, we'll be discussing about the sequences, pre-requisites for good reporting, pattern of reporting and normal MRI anatomy of the ankle. The sequences for a routine ankle MRI consist of T2 fat saturated sagittal images, proton density non-fat saturated images in all the three planes and T2 fat saturated axial images. T1 weighted images are not obtained as a part of routine ankle MRI done for internal derangements of sports injuries. But T1 weighted images are required for imaging in tumours, infection and inflammatory conditions. Precisely because as you can see, the cartilage is not well seen on T1 images. Also, the ligaments have a poor resolution and it is difficult to identify ligament injuries on T1 weighted images. For good reporting, you need good quality images. And if you have a good quality scan, you're more than half the job is done. So 3 Tesla MRI is better than 1.5 Tesla, but good quality images can also be obtained on 1.5 Tesla scanner. Always have a small FOV. If you are imaging the ankle, then just image the ankle and not the entire leg or the foot. Call in the application specialist and set appropriate protocols for the scan. At least get minimum 3mm thickness images because with thicker sections, the resolution is less, especially when you have to image small and thin ligaments like in the ankle and obtain the images with 0mm slice gap. Always make it a point to put a pain marker at the site of pain or swelling in the patient as this will give you an idea as to which pathology is causing the symptoms to the patient. Remember we treat the patient and not the MRI scan. Always have a pattern of reporting for any joint MRI and follow that pattern in day to day life so that you don't miss anything. The pattern that I follow for the ankle joint is the inside out pattern, that is I look at the inner structures first and then work my way outwards. So first you look at the bones, then joint and cartilage followed by ligaments, tendons, then neurovascular structures and tarsal tunnel and finally miscellaneous structures that is plantar fascia and sinus tarsis. The ligaments in the ankle can be divided into high ankle and low ankle ligaments and spring or calcaneo-navicular ligament. High ankle ligaments consist of anterior and posterior tibiafibular and syndesmotic ligaments. It is important to identify injuries to the high ankle ligaments. Low ankle ligaments consist of lateral and medial ligament complexes. Laterally you have the anterior and posterior tibiafibular ligaments and calcaneo-navicular ligament. Medially is the deltoid ligament which consists of deep and superficial fibres. Tendons can be divided into four compartments that is anterior, medial, lateral and posterior. So now we will look at all of these normal structures in a normal MRI scan in all the three planes. First we obviously as I said we take the T2 fat saturated sagittal images, look for bone marrow edema, soft tissue edema, joint effusion or fluid along the tendon sheath on these images. This will help you to localize the area of abnormality and the ankle joint and then you can look at the proton density images for the cause of the abnormality. So these are the proton density non-fat saturated sagittal images. This is the scout image which will help you to guide us to which level are we looking at and as we go from medial to lateral the first structure that we see is the medial medialis. Behind the medial medialis is a thick jet black tendon which is the tibialis posterior tendon which goes in attaches to the navicular bone and these two structures are nothing but the accessory navicular bones. Now as we go further towards the midline you can see the tibia articulating with the talus and the talus articulating with the calcaneo. This is the tibiotalar joint. The grey colored zone is nothing but the tibiotalar cartilage and this is the subtalar joint between the talus and the calcaneum. The subtalar joint consists of three parts that is the anterior, mid and posterior subtalar joint. This is the posterior subtalar joint and again you can very well identify the talar as well as the calcaneum cartilage on the proton density images. Now again we'll come back immediately and you see another joint between the talus and the calcaneum and this is the mid subtalar joint. The anterior subtalar joint is not that important. Talus consists of the talar dome and the head and neck region. The talus articulates with another bone which is the navicular bone and this is the talonavicular joint and as you go laterally you see the calcaneum and this is the anterior process of the calcaneum. Further laterally the calcaneum articulates with the cuboid and this is the calcaneum cuboid joint. Now as you go further laterally you see the fibula. This is the lateral medulus and there are two tendons that are seen posterior to the lateral medulus in the retro medula region and the tendon that goes and attaches to the base of the fifth metatarsal. This is the peroneus brevis tendon and the other tendon is the peroneus longus tendon which goes along the plantar aspect of the foot. Now we have discussed about the bones, joints, cartilage and few of the tendons. The ligaments are not well seen on sagittal images and we'll discuss them on the axial and coronal images but there are three other structures which are important and well seen on sagittal images and we look at those one by one. So again we are going from medial to lateral and as we do so you can see a thick jet black hyper intense band along the plantar surface of the foot that goes and attaches to the inferior aspect of calcaneum. This is nothing but the plantar fascia. Plantar fascia consists of three bands medial, central and lateral. The medial band is smaller, this thick band is nothing but the central band and as you go further laterally you see another band that is attaching to the calcaneum which is thinner than the central band and this is the lateral band of the plantar fascia. The second important structure is this thick tendon that goes and attaches to the posterior aspect of the calcaneum and this is the achilles tendon and the muscle adjoining it is the soleus muscle. Always look for any oscius bump in the calcaneum in this region which would indicate a haggle and deformity. There is a small retrocalcaneal bursa in this region. Thin silver of fluid within the bursa is normal. Significant amount of fluid would indicate a pathology in that region. The third structure that is seen on the sagittal image is between the tailors and the calcaneum and this is nothing but the sinus starsi. Sinus starsi is hyper intense on proton density images because it predominantly consists of fat along with small ligaments like cervical ligament and neurovascular bundles. Now because it contains mainly fat it appears hyper intense on the fat saturated images and any edema or fluid within the sinus starsi would indicate sinus starsi degeneration which can occur in multiple conditions. So we've discussed the imaging in sagittal images. Now we look at the axial images and again we'll be going from superior to inferior. First we look at the bones. So this larger bone in the cross section is tibia and the smaller one is the fibula. The cartilage and the joint is not well seen on axial images. So next we look at the ligaments and as you go from superior to inferior you can see thin flimsy hyper intense bands that are coming from the tibia and going towards the fibula obliquely and these are nothing but the sin dysmotic ligaments. Now as you go further inferiorly at the level where the tibia is ending and the talus is about to start you can see thin hyper intense bands both anteriorly and posteriorly bridging between the tibia and the fibula. This is the anterior and this is the posterior tibia fibular ligaments which also run obliquely. The key to identify the level at which these ligaments are seen is when the talus has a squared appearance. Now these three ligaments that is the anterior and posterior tibia fibular and sin dysmotic ligaments are high ankle ligaments and it is important to identify injury to these ligaments because the management can change from a conservative to a surgical one when these ligaments get injured. Now as you go further inferiorly where at the place where the talus has a figure of eight appearance a thick band is seen between the talus and the fibula and this is the anterior tibia fibular ligament posteriorly you have the posterior tibia fibular ligament. Some hyper intense signal is seen with a striated appearance towards the fibular attachment of the posterior tibia fibular ligament and this is normal appearance and it should not be mistaken for a tear or an injury. Remember the posterior tibia fibular ligament is one of the last ligaments to get injured in your ankle sprain. Now as we go further inferiorly you can see a ligament bridging between the navicular bone and the calcaneum bone and this is the calcaneum navicular ligament or the spring ligament. Now there are other few ligaments which are better seen on the coronal images and we'll discuss it there. Now we'll look at the tendons again we are going from superior to inferior and the first compartment that we'll discuss is the medial compartment which consists of three tendons. Remember the medial most tendon beat anterior or posterior is the tibialis tendon. So this is the tibialis posterior tendon now it is like Tom, Dick and Harry so this will be flexor digitorum longus and this is flexor halosus longus. Between these two tendons you have the posterior neurovascular bundle. Remember the tibialis posterior is nearly double the size of the other two tendons. Now as you go inferiorly this is the tarsal tunnel which consists of the posterior neurovascular bundle. In this section you can see there is an auspicious prominence along the posterior aspect of the talus which is the posterior tular process. It forms a groove within which a tendon is sitting and that is the flexor halosus longus tendon. Sometimes there are large posterior tular osteophytes or a strikonum which can cause impingement on this tendon and resulting into posterior impingement syndrome. Now we'll concentrate on the tibialis posterior tendon as we go inferiorly. It has a wide attachment to the navicular bone and these two auspicious structures within the tibialis posterior tendon are the accessory navicular bones. Now again we'll go from superior to inferior but this time we'll look at the lateral compartment which consists of two tendons the peroneus brevis and the longus tendon. The key to remember is B for bone and B for brevis. So the tendon that is close to the bone is the peroneus brevis tendon and the tendon that is lateral is the longest tendon. Superficial to these two tendons is a thin hyper intense band which is the superior peroneal retinaculum. It is important to identify injuries to this retinaculum because it can result in two peroneal tendon dislocations or subluxations. Now as you go further inferiorly another thin hyper intense band is seen overlying these two tendons at the level of the calcaneum and this is the inferior peroneal retinaculum. Now further on the two tendons are seen separately where the peroneus brevis tendon will go and attach to the base of the fifth metatarsal and the peroneus longest tendon will go along the plantar surface of the foot. So that is the attachment of the peroneal brevis tendon. Now again we'll come from superior to inferior but this time we'll look at the anterior or the extensor compartment. It also consists of three tendons and as I said the medial most tendon is the tbls one. So this is the tbls anterior. Here it is tom, dick and harry. Anteriorly the relation is reversed so it becomes tom, harry and dick and so this is extensor halosus longest tendon and this is the extensor digitorum longest tendon. Remember the extensor tendons are less involved as compared to the medial flexors or the peroneal tendons. And the last or the fourth compartment is the posterior compartment. This thick tbls tendon is the achilles tendon and adjoining is the soleus muscle. Now another important structure is this thin hyper intense linear band that goes along with the achilles tendon and this is the plantarus tendon. It is important because sometimes it is mistaken for a splitter in the achilles tendon. Now as you go inferiorly the achilles tendon goes and attaches to the calcaneum. So we've discussed the imaging on the achilles plains. Now we'll look at the coronal plains and this time we are going from anterior to posterior and again first we'll look at the bones and the cartilage. So this is tbls, this is tbls and this is the tbls tailar joint. Make sure to look at the medial and the lateral tailar domes for any osteocondrial lesions. Now medially as I said we have the medial ligament complex which comprises of the deltoid ligament and these are the deep fibres of the deltoid which go from the tbls to the talus, from the medial medulus to the talus and this is the tbls tailar ligament. It normally has this striated appearance and hyper intense signal within because of the fanning out of the fibres just like the posterior tbls ligament and this should not be mistaken for a tear. And deltoid fibres also consist of superficial fibres which go from tbls to the calcaneum, navicular and the spring ligaments but the deep fibres are clinically more important. So we have discussed the low ankle ligaments that is anterior and posterior tbls ligament on the axial images. On the coronal images we look at the calcaneum fibular ligament which is a thick ligament towards the fibular attachment and it becomes thin towards the calcaneal attachment. This ligament is present deep to the peroneal tendons. It is an oblique ligament and so as you go posteriorly you can see it goes towards the calcaneum and has a thin attachment towards the calcaneum. The next is the plantar fascia and these is the central band of the plantar fascia and this is the lateral band of the plantar fascia and it goes and attaches to the calcaneum and the posterior most structure is obviously the Achilles tendon. So we have discussed the normal appearances of the structures in an ankle joint on the MRI and this is a checklist of those structures which are better seen on sagittal, axial and the coronal images. But just remember that please make sure to look at these structures on other planes as well, particularly when you are in doubt whether they are injured or not. Thank you for watching my video. Hope this will help you to understand the basics of how to read an ankle MRI and if this has helped you then stay tuned for my next video on ankle sprain which will be updated very soon.