RADIOLOGICAL IMAGING: Plain Radiography. Ultrasonography (US). Computed Tomography (CT). Magnetic Resonance Imaging(MRI).

The hip joint is located where the thigh bone (femur) meets the pelvic bone. It is a ball and socket joint. The upper end of the femur is formed into a round ball (the head of the femur). A cavity in the pelvic bone forms the socket (acetabulum). The ball is normally held in the socket by very powerful ligaments that form a complete sleeve around the joint (the joint capsule). The capsule has a delicate lining (the synovium). The head of the femur is covered with a layer of smooth cartilage which is a fairly soft, white substance about 1/8 inch thick. The socket is also lined with cartilage (also about 1/8 inch thick). The cartilage cushions the joint, and allows the bones to move on each other with very little friction. An x-ray of the hip joint usually shows a space between the ball and the socket because the cartilage does not show up on x-rays. In the normal hip this joint space is approximately 1/4 inch wide and fairly even in outline.

LigamentsThe ligaments of the hip joint act to increase stability. They can be divided into two groups – intracapsular and extracapsular.

IntracapsularThe only intracapsular ligament is the ligament of head of femur. It is a relatively small ligament that runs from the acetabular fossa to the fovea of the femur. It encloses a branch of the oburator artery, which comprises a small proportion of the hip joint blood.

ExtracapsularThere are three extracapsular ligaments. They are continuous with the outer surface of the hip joint capsule.Iliofemoral: Located anteriorly. It originates from the ilium, immediately inferior to the anterior inferior iliac spine. The ligament attaches to the intertrochanteric line in two places, giving the ligament a Y shaped appearance. It prevents hyperextension of the hip joint.Pubofemoral: Located anteriorly and inferiorly. It attaches at the pelvis to the iliopubic eminance and obturator membrane, and then blends with the articular capsule. It prevents excessive abduction and extension.Ischiofemoral: Located posteriorly. It originates from the ischium of the pelvis and attaches to the greater trochanter of the femur. It prevents excessive extension of the femur at the hip joint.

Neurovascular Structures.

Vascular supply to the hip joint is achieved via the medial and lateral circumflex femoral arteries, and the artery to head of femur.The circumflex arteries are branches of the profunda femoris artery. They anastamose at the base of the femoral neck to form a ring, from which smaller arteries arise to the supply the joint itself.The medial circumflex femoral artery is responsible for the majority of the arterial supply (the lateral circumflex femoral artery has to penetrate through the thick iliofemoral ligament to reach the hip joint). Damage to the medial circumflex femoral artery can result in avascular necrosis of the femoral head.The hip joint is innervated by the femoral nerve, obturator nerve, superior gluteal nerve, and nerve to quadratus femoris.

1. Lateral part of the sacrum2. Gas in colon3. Ilium4. Sacroiliac joint5. Ischial spine6. Superior ramus of pubis7. Inferior ramus of pubis8. Ischial tuberosity9. Obturator foramen10. Intertrochanteric crest11. Pubic symphysis12. Pubic tubercle13. Lesser trochanter14. Neck of femur15. Greater trochanter16. Head of femur17. Acetabular fossa18. Anterior inferior iliac spine19. Anterior superior iliac spine20. Posterior inferior iliac spine21. Posterior superior iliac spine22. Iliac crest

1. Anterior superior iliac spine2. Ilium3. Anterior inferior iliac spine4. Pelvic brim5. Acetabular fossa6. Head of femur7. Fovea8. Superior ramus of pubis9. Obturator foramen10. Inferior ramus of pubis11. Pubic symphysis12. Ischium13. Lesser trochanter14. Intertrochanteric crest15. Greater trochanter16. Neck of femur

1. Greater trochanter2. Intertrochanteric crest3. Lesser trochanter4. Neck of femur5. Head of femur6. Acetabular fossa7. Superior ramus of pubis8. Obturator foramen9. Inferior ramus of pubis10. Ischium

Pelvis anatomy - Normal AP The 2 hemi-pelvis bones and the sacrum form a bone ring bound posteriorly by the sacroiliac joints and anteriorly by the pubic symphysis Each obturator foramen is also formed by a ring of bone.

Hemi-pelvis anatomy - Normal AP Each hemi-pelvis bone comprises 3 bones - the ilium (white), pubis (orange) and ischium (blue) The 3 bones fuse to form the acetabulum - the pelvic portion of the hip jointASIS = Anterior Superior Iliac Spine = attachment site for sartorius muscleAIIS = Anterior Inferior Iliac Spine = attachment site for rectus femoris muscle

Hip X-ray anatomy - Normal AP

Shenton's line is formed by the medial edge of the femoral neck and the inferior edge of the superior pubic ramusLoss of contour of Shenton's line is a sign of a fractured neck of femur

Hip X-ray anatomy - Normal Lateral

The cortex of the proximal femur is intact.The Lateral view is often not so clear because those with hip pain find the positioning required difficult .

Intracapsular v extracapsular

The capsule envelopes the femoral head and neckSubcapital, transcervical and basicervical fractures are intracapsular hip injuriesIntertrochanteric and subtrochanteric fractures do not involve the neck of femur.

Pelvis anatomy - Normal AP The 2 hemi-pelvis bones and the sacrum form a bone ring bound posteriorly by the sacroiliac joints and anteriorly by the pubic symphysis Each obturator foramen is also formed by a ring of bone.

Hemi-pelvis anatomy - Normal AP Each hemi-pelvis bone comprises 3 bones - the ilium (white), pubis (orange) and ischium (blue) The 3 bones fuse to form the acetabulum - the pelvic portion of the hip jointASIS = Anterior Superior Iliac Spine = attachment site for sartorius muscleAIIS = Anterior Inferior Iliac Spine = attachment site for rectus femoris muscle

A, C) US scans obtained at the proximal tendon of the rectus femoris (A) and at the proximal myotendinous junction (B). (B, D) T1-weighted MRI images corresponding to the US scans. US provides visualization of the direct tendon (black arrows) and the indirect tendon (white arrows) of the rectus femoris. In A, the posterior shadow cone of the tendon is an indirect consequence of its obliquity. At the rectus femoris myotendinous junction (DA), it is inserted on to the lateral surface of the direct tendon. TFL: tensor fasciae latae muscle; Sat: sartorius muscle; IP: iliopsoas muscle; PGL: small gluteal muscle.

(US images on the left): US Sagittal scan obtained at the direct tendon (black arrows) and indirect tendon (white arrows) of the rectus femoris muscle (RF). The image on the top was obtained by scanning at the medial level as compared to the image below. (MR images on the right): T1-weighted MR image corresponding to the US scans. The direct tendon shows a homogeneous and hyperechoic appearance. Its insertion on to the anterior-inferior iliac spine is well visible on the US image. In physiological conditions the tendon is thicker just before insertion. In B, the indirect tendon appears hypoechoic because of anisotropy.

(US images on the left): US Sagittal scan obtained at the direct tendon (black arrows) and indirect tendon (white arrows) of the rectus femoris muscle (RF). The image on the top was obtained by scanning at the medial level as compared to the image below. (MR images on the right): T1-weighted MR image corresponding to the US scans. The direct tendon shows a homogeneous and hyperechoic appearance. Its insertion on to the anterior-inferior iliac spine is well visible on the US image. In physiological conditions the tendon is thicker just before insertion. In B, the indirect tendon appears hypoechoic because of anisotropy.

(US images on the left): US oblique axial scans obtained at the femoral neck (top) and the femoral head (below). (MR images on the right): T1-weighted MR images corresponding to the US scans. The ileofemoralligament appears as a hyperechoic band (curved arrow) in front of the femoral neck (CF). C, D: at the femoral head, the ligament appearing as a fibrillar structure (white arrow) is inserted on to the front edge of the cup near the anterior acetabular labrum (arrowheads). IP: iliopsoas muscle; Sa: sartorius muscle; RF: rectus femoris.

(A, B): US scans obtained at the femoral vessels. (C): T1-weighted MR image corresponding to the US scans. US provides visualization of the common femoral artery (white arrows), the common femoral nerve traveling outside the artery (black arrows) and the common femoral vein inside (empty arrow).

(A, C): axial US scans carried out at the gluteus muscles and their insertion on to the greater trochanter. (B, D): T1-weighted MR images corresponding to the US scans. US provides visualization of the gluteus medius muscle (MG) and the deeper located gluteus minimus muscle (PG). The image obtained at the level of the tendons provides distinction between the tendon of the gluteus minimus muscle (black arrow) traveling in front of the tendon of the gluteus medius muscle (white arrow). Arrowhead: fasciae latae. VE = external vastus muscle (quadriceps muscle).

(US images on the left): Coronal US scans carried out at the lateral surface of the hip. (MR images on the right): T1-weighted MR images corresponding to the US scans. • Photo, top = anterior image shows the tendon of the gluteus minimus muscle (black arrow) that inserts on to the lateral surface of the greater trochanter. Arrowhead: fasciae latae. • Photo, mid = image obtained at the middle third of the greater trochanter shows the anterior tendon of the gluteus medius muscle (white arrow). Arrowhead: fasciae latae. • Photo, bottom = posterior image shows the posterior tendon of the gluteus medius muscle (empty arrow) which inserts on to the apex of the greater trochanter.

Osseous AnatomyThe pelvis is formed by the two innominate bones that articulate posteriorly with the sacrum at the sacroiliac joints and anteriorly at the pubic symphysis. Each innominate bone is composed of an ilium, ischium, and pubis. The acetabulum is formed by the junction of these osseous structures. The posterior acetabulum is stronger and along with the dome comprises the weight-bearing portion of the acetabulum. The margin of the acetabulum is surrounded by a fibrocartilaginous labrum. The hip is a ball and socket joint. The fibrous capsule of the hip joint is lined with synovial membrane and the hyaline cartilage covers the articular surfaces of the acetabulum and femoral head. There are several important intra-articular structures that should be identified on MR images. Ligamentum teres is a firm ligament extending from the fovea of the femoral head to the acetabulum. The ligament enters a small notch in the medial acetabular wall where it is surrounded by fat.

Muscular AnatomyThe anatomy of the muscles acting on the pelvis, hips, and thighs in axial, coronal, sagittal, and even oblique planes must be thoroughly understood to interpret MR images and evaluate symptoms related to these structures. The muscles acting on the hip joint per se are numerous. Therefore, it is simplest to discuss them based upon their function. The chief extensors of the hip include the gluteus maximus and posterior portion of the adductor magnus. Extension is also accomplished to some degree by assistance from the semimembranosus, semitendinosus, biceps femoris, gluteus medius, and gluteus minimus The primary flexor of the hip is the iliopsoas muscle. However, the pectineus, tensor fasciae latae, adductor brevis, and sartorius also function in this regard. Accessory flexors include the adductor longus, adductor magnus, gracilis, and gluteus minimus. The iliacus and psoas muscle anatomy is important for accurate interpretation of MR images. The bulk of the iliacus muscle run parallel to the iliopsoas tendon and attach to the proximal femur. In some cases, a small iliacus tendon runs parallel to the iliopsoas tendon as it attaches to the lesser trochanter. The iliopsoas tendon is separated from the iliacus muscle and tendon by a small amount of fatty tissue.

Radiographic AnatomyThe knee joint is composed of three articulations: the medial and lateral femorotibial and patellofemoral articulations. Although they share a common joint capsule, these articulations are often referred to separately as the medial, lateral, and patellofemoral compartments or joints. An anteroposterior (AP) knee radiograph shows the femoral condyles and tibial plateaus. The medial and lateral compartment radiolucent “joint spaces” or “cartilage spaces” should be equal with the knee extended; asymmetry usually indicates cartilage loss, ligamentous laxity, or both. Standing views may accentuate such findings. A standing view with the knees slightly flexed can be even better at demonstrating cartilage loss not evident with the knee fully extended, because earlier and more severe cartilage loss often occurs along the posterior weight-bearing portions of the femoral condyles. A lateral radiograph profiles the anterior weight-bearing, mid–weight-bearing, and posterior weight-bearing surfaces of the femoral condyles and also reveals differences between the condyles and tibial plateaus.

ROLE OF ULTRASOUND Ultrasound is essentially used for the external structures of the knee. Ultrasound is a valuable diagnostic tool in assessing the following indications; Muscular, tendinous and ligamentous damage (chronic and acute) Bursitis Joint effusion Popliteal vascular pathology Haematomas Masses such as Baker’s cysts, lipomas Classification of a mass e.g solid, cystic, mixed Post surgical complications e.g abscess, edema Guidance of injection, aspiration or biopsy Relationship of normal anatomy and pathology to each other Some boney pathology.

LIMITATIONSIt is recognised that ultrasound offers little or no diagnostic information for internal structures such as the cruciate ligaments. Ultrasound is complementary with other modalities, including plain X-ray, CT, MRI and arthroscopy.

Transverse suprapatella region:•RF: Rectus Femoris •VI: Vastus intermedius•VL: Vastus Lateralis •VM: Vastus Medialis

Longitudinal suprapatella region showing the suprapatella bursa and quadriceps tendon.

The infra-patellar tendon.

Transverse Infrapatellar tendon. Note how wide it is, to then have an understanding of the area you need to examine in longitudinal.

Pes Anserine tendons. The medial collateral ligament (green) directly overlying the medial meniscus (purple).

Assess the Lateral collateral ligament, Ilio-Tibial band insertion and peripheral margins of the lateral meniscus. Unlike the medial side, the LCL is separated from the meniscus by a thin issue plane.

Medial aspect of the popliteal fossa showing the semimembranosis/gastrocnemius plane

Ultrasound of the Popliteal vein and artery in transverse. Without and with

compression to exclude DVT.

Confirm both arterial and venous flow and exclude a popliteal artery aneurysm. If a Popliteal aneurysm is discovered, always extend the examination to the other leg and the abdomen. There is a risk of bilateral and high association with aortic aneurysm.

The knee joint joins the thigh with the leg and consists of two

articulations: one between the femur and tibia, and one between the femur and patella.

The articular bodies of the femur are its lateral and medial condyles. These diverge slightly distally and posteriorly, with the lateral condyle being wider in front than at the back while the medial condyle is of more constant width. The radius of the condyles' curvature in the sagittal planebecomes smaller toward the back. This diminishing radius produces a series of involute midpoints (i.e. located on a spiral). The resulting series of transverse axes permit the sliding and rolling motion in the flexing knee while ensuring the collateral ligaments are sufficiently lax to permit the rotation associated with the curvature of the medial condyle about a vertical axis.The pair of tibial condyles are separated by the intercondylar eminence composed of a lateral and a medial tubercle.The patella is inserted into the thin anterior wall of the joint capsule. On its posterior surface is a lateral and a medial articular surface, both of which communicate with the patellar surface which unites the two femoral condyles on the anterior side of the bone's distal end.

The knee is a hinge type synovial joint, which is composed of three functional

compartments: the femoropatellar articulation, consisting of the patella, or "kneecap", and the patellar groove on the front of the femur through which it slides; and the medial and lateral femorotibial articulations linking the femur, or thigh bone, with the tibia, the main bone of the lower leg. The joint is bathed in synovial fluid which is contained inside the synovial membrane called the joint capsule. The posterolateral corner of the knee is an area that has recently been the subject of renewed scrutiny and research.The knee is one of the most important joints of our body. It plays an essential role in movement related to carrying the body weight in horizontal (running and walking) and vertical (jumps) directions.At birth, a baby will not have a conventional knee cap, but a growth formed of cartilage. By the time that the child is 3–5 years of age, ossification will have replaced the cartilage with bone. Because it is the largest sesamoid bone in the human body, the ossification process takes significantly longer.

Bursae: Numerous bursae surround the knee joint. The largest

communicative bursa is the suprapatellar bursa described above. Four considerably smaller bursae are located on the back of the knee. Two non-communicative bursae are located in front of the patella and below the patellar tendon, and others are sometimes present.

Cartilage.Cartilage is a thin, elastic tissue that protects the bone and makes certain that the joint surfaces can slide easily over each other. Cartilage ensures supple knee movement. There are two types of joint cartilage in the knees: fibrous cartilage (the meniscus) and hyaline cartilage. Fibrous cartilage has tensile strength and can resist pressure. Hyaline cartilage covers the surface along which the joints move. Cartilage will wear over the years. Cartilage has a very limited capacity for self-restoration. The newly formed tissue will generally consist of a large part of fibrous cartilage of lesser quality than the original hyaline cartilage. As a result, new cracks and tears will form in the cartilage over time.

MenisciThe articular disks of the knee-joint are called menisci because they only partly divide the joint space. These two disks, the medial meniscus and the lateral meniscus, consist of connective tissue with extensive collagen fibers containing cartilage-like cells. Strong fibers run along the menisci from one attachment to the other, while weaker radial fibers are interlaced with the former. The menisci are flattened at the center of the knee joint, fused with the synovial membrane laterally, and can move over the tibial surface. The menisci serve to protect the ends of the bones from rubbing on each other and to effectively deepen the tibial sockets into which the femur attaches. They also play a role in shock absorption, and may be cracked, or torn, when the knee is forcefully rotated and/or bent.

Ligaments:Intracapsular.The knee is stabilized by a pair of cruciate ligaments. The anterior cruciate ligament (ACL) stretches from the lateral condyle of femur to the anterior intercondylar area. The ACL is critically important because it prevents the tibia from being pushed too far anterior relative to the femur. It is often torn during twisting or bending of the knee. The posterior cruciate ligament (PCL) stretches from medial condyle of femur to the posterior intercondylar area. Injury to this ligament is uncommon but can occur as a direct result of forced trauma to the ligament. This ligament prevents posterior displacement of the tibia relative to the femur.The transverse ligament stretches from the lateral meniscus to the medial meniscus. It passes in front of the menisci. It is divided into several strips in 10% of cases. The two menisci are attached to each other anteriorly by the ligament. The posterior and anterior meniscofemoral ligaments stretch from the posterior horn of the lateral meniscus to the medial femoral condyle. They pass posteriorly behind the posterior cruciate ligament. The posterior meniscofemoral ligament is more commonly present (30%); both ligaments are present less often. The meniscotibial ligaments (or "coronary") stretches from inferior edges of the mensici to the periphery of the tibial plateaus.

Extracapsular.The patellar ligament connects the patella to the tuberosity of the tibia. It is also occasionally called the patellar tendon because there is no definite separation between the quadriceps tendon (which surrounds the patella) and the area connecting the patella to the tibia. This very strong ligament helps give the patella its mechanical leverage and also functions as a cap for the condyles of the femur. Laterally and medially to the patellar ligament the lateral and medial patellar retinacula connect fibers from the vasti lateralisand medialis muscles to the tibia. Some fibers from the iliotibial tract radiate into the lateral retinaculum and the medial retinaculum receives some transverse fibers arising on the medial femoral epicondyle. The medial collateral ligament (MCL a.k.a. "tibial") stretches from the medial epicondyle of the femur to the medial tibial condyle. It is composed of three groups of fibers, one stretching between the two bones, and two fused with the medial meniscus. The MCL is partly covered by the pes anserinus and the tendon of the semimembranosus passes under it. It protects the medial side of the knee from being bent open by a stress applied to the lateral side of the knee (a valgus force). The lateral collateral ligament stretches from the lateral epicondyle of the femur to the head of fibula. It is separate from both the joint capsule and the lateral meniscus. It protects the lateral side from an inside bending force (a varus force). The anterolateral ligament (ALL) is situated in front of the LCL. Lastly, there are two ligaments on the dorsal side of the knee. The oblique popliteal ligament is a radiation of the tendon of the semimembranosuson the medial side, from where it is direct laterally and proximally. The arcuate popliteal ligament originates on the apex of the head of the fibula to stretch proximally, crosses the tendon of the popliteus muscle, and passes into the capsule.

The ankle joint or “talocrural joint” is a synovial hinge joint that is

made up of the articulation of 3 bones. The 3 bones are the tibia, the fibula and the talus. The articulations are between the talus and the tibia and the talus and the fibula. The “mortise” is the concaved surface formed by the tibia and fibula. The mortise is adjustable and is controlled by the proximal and distal tibiofibular joints. The talus articulates with this surface and allows dorsiflexion and plantar flexion. Most congruent joint in the body. It allows in open chain activity (non-weight bearing), the convex talus slides posteriorly during dorsiflexion and anteriorly during plantar flexion on the concave tibia and fibula.In closed chain activity (weight bearing), the tibia and fibula move on the talus. Subtalar joint:Also known as the talocalcaneal joint. It is a triplanar, uniaxial joint which allows 1°of freedom: supination(closed packed position) and pronation(open). Supination is accompanied by calcaneal inversion (calcaneovarus) and pronation is accompanied by calcaneal eversion (calcaneovalgus).

Ultrasound of the ankle:For specific indications, ultrasound (US) is an efficient and inexpensive alternative to magnetic resonance (MR) imaging for evaluation of the ankle. In addition to the tendons and tendon sheaths, other ankle structures demonstrated with US include the anterior joint space, retrocalcaneal bursa, ligaments, and plantar fascia. Ankle US allows detection of tenosynovitis and tendinitis, as well as partial and complete tendon tears. Joint effusions, intraarticular bodies, ganglion cysts, ligamentous tears, and plantar fasciitis can also be diagnosed. As pressure for cost containment continues, demand for US of the ankle may increase given its lower cost compared with that of MR imaging. In most cases, a focused ankle US examination can be performed more rapidly and efficiently than MR imaging. Familiarity with the technique of ankle US, normal US anatomy, and the US appearances of pathologic conditions will establish the role of US as an effective method of imaging the ankle.

Peroneus longus and brevis tendons. Transverse at the medial malleolus.

Peroneus brevis insertion ontothe base of the 5th metatarsal.

Calcaneo-fibular ligament Anterior Talo-fibula ligament (ATFL).

Normal Tibio fibula ligament. Extensor digitorum tendon

Longitudinal extensor hallucis longus tendon. Longitudinal Tibialis Anterior tendon.

Tibialis posterior, flexor Digitorum and flexor Hallucis longus tendons (known as "Tom, Dick & Harry"). If including the neurovascular bundle - Tom Dick And Very Nervous Harry. Deltoid ligament

Normal Achilles tendon longitudinal panorama

The ankle joint acts like a hinge. But it's much more than a simple

hinge joint. The ankle is actually made up of several important

structures. The unique design of the ankle makes it a very stable joint.

This joint has to be stable in order to withstand 1.5 times your body

weight when you walk and up to eight times your body weight when

you run. Normal ankle function is needed to walk with a smooth and

nearly effortless gait.

The muscles, tendons, and ligaments that support the ankle joint work

together to propel the body. Conditions that disturb the normal way

the ankle works can make it difficult to do your activities without pain

or problems.

This guide will help you understand what parts make up the ankle

•Important StructuresThe important structures of the ankle can be divided into several

categories. These include

•bones and joints.

•ligaments and tendons.

•Muscles.

•Nerves.

•blood vessels.

The ankle, or the talocrural region, is the region where the foot and the leg meet.

The ankle includes three joints: the ankle joint proper or talocrural joint, the subtalar joint, and the Inferior tibiofibular joint. The movements produced at this joint are dorsiflexion and plantarflexion of the foot. In common usage, the term ankle refers exclusively to the ankle region. In medical terminology, "ankle" (without qualifiers) can refer broadly to the region or specifically to the talocrural joint.The main bones of the ankle region are the talus (in the foot), and the tibia and fibula(in the leg). The talus is also called the ankle bone. The talocrural joint is a synovialhinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus. The articulation between the tibia and the talus bears more weight than that between the smaller fibula and the talus. The bony architecture of the ankle consists of three bones: the tibia, the fibula, and the talus. The articular surface of the tibia is referred to as the plafond. The medial malleolus is a bony process extending distally off the medial tibia. The distal-most aspect of the fibula is called the lateral malleolus. Together, the malleoli, along with their supporting ligaments, stabilize the talus underneath the tibia.The bony arch formed by the tibial plafond and the two malleoli is referred to as the ankle "mortise" (or talar mortise). The mortise is a rectangular socket. The ankle is composed of three joints: the talocrural joint (also called tibiotalar joint, talar mortise, talar joint), the subtalar joint (also called talocalcaneal), and the Inferior tibiofibular joint. The joint surface of all bones in the ankle are covered with articular cartilage.

Ligaments.The ankle joint is bound by the strong deltoid ligament and three lateral ligaments: the anterior talofibular ligament, the posterior talofibular ligament, and the calcaneofibular ligament.The deltoid ligament supports the medial side of the joint, and is attached at the medial malleolus of the tibia and connect in four places to the sustentaculum tali of the calcaneus, calcaneonavicular ligament, the navicular tuberosity, and to the medial surface of the talus.The anterior and posterior talofibular ligaments support the lateral side of the joint from the lateral malleolus of the fibula to the dorsal and ventral ends of the talus.The calcaneofibular ligament is attached at the lateral malleolus and to the lateral surface of the calcaneous.Though it does not span across the ankle joint itself, the syndesmotic ligament makes an important contribution to the stability of the ankle. This ligament spans the syndesmosis, which is the term for the articulation between the medial aspect of the distal fibula and the lateral aspect of the distal tibia. An isolated injury to this ligament is often called a high ankle sprain.The bony architecture of the ankle joint is most stable in dorsiflexion. Thus, a sprained ankle is more likely to occur when the ankle is plantar-flexed, as ligamentous support is more important in this position. The classic ankle sprain involves the anterior talofibular ligament (ATFL), which is also the most commonly injured ligament during inversionsprains. Another ligament that can be injured in a severe ankle sprain is the calcaneofibular ligament.

Thank You.