The anatomical snuff box is a surface anatomy feature. It appears as a triangular depression on the lateral surface of the wrist on full extension of the thumb.
medial: tendons of the extensor pollicis longus
lateral: tendons of the
extensor pollicis brevis
The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge for radiologists and imaging specialists.
Head and neck anatomy
Abdominal and pelvic anatomy
The anconeus is a small muscle in the posterior compartment of the arm at the lateral aspect of the elbow. It has little functional significance but should be differentiated from the variably present anconeus epitrochlearis at the medial aspect of the elbow.
origin: lateral epicondyle ...
Anconeus epitrochlearis is an accessory muscle at the medial aspect of the elbow. It is also known as the accessory anconeus muscle and should not be confused with the anconeus muscle which is present at the lateral aspect of the elbow.
The muscle may be unilateral but has been f...
The Anderson and D'Alonzo classification is the most commonly used classification of fractures of the odontoid process of C2.
fracture of the upper part of the odontoid peg
above the level of the transverse band of the cruciform ligament
usually considered stable...
Andersson lesions refer to an inflammatory involvement of the intervertebral discs by spondyloarthritis.
Rheumatic spondylodiscitis is a non-infectious condition that has been shown to occur in about 8% of patients with ankylosing spondylitis, as detected at radiography.
Aneurysmal bone cysts (ABC) are benign expansile tumour-like bone lesions of uncertain aetiology, composed of numerous blood-filled channels, and mostly diagnosed in children and adolescents.
Aneurysmal bone cysts are primarily seen in children and adolescents, with 80% occurring ...
Angiolipomas (also sometimes known as haemangiolipomas, vascular lipomas, and fibromyolipomas) are rare soft tissue tumours composed of mature adipocytes and vessels. They can occur essentially anywhere and can be subclassified into infiltrating and non-infiltrating variants 1.
Please refer to...
Angiosarcoma of bone is a malignant vascular tumour of bone. These are rare and account for less than 1% of malignant bone tumours. The majority of these tumours arising in bone are primary; however, a tiny percentage is either radiation-induced or associated with bone infarction
The angle of the longitudinal arch is one of the angles drawn on the weightbearing lateral foot radiograph. The angle is formed between the calcaneal inclination axis and a line drawn along the inferior edge of the 5th metatarsal.
The normal angle is 150-170°.
In pes cavus, as the height of th...
Anisotropy is an artefact encountered in ultrasound, notably in muscles and tendons during a musculoskeletal ultrasound. In musculoskeletal applications, the artefact may prompt an incorrect diagnosis of tendinosis or tendon tear.
When the ultrasound beam is incident on a fibrillar structure as...
Ankle AP view is part of a three view series of the distal tibia, distal fibula, proximal talus and proximal metatarsals.
the patient may be supine or sitting upright with their leg straighten on the table
the foot is in dorsiflexion
the toes will be pointing directly toward...
Ankle fractures account for ~10% of fractures encountered in trauma, preceded only in incidence by proximal femoral fractures in the lower limb. They have a bimodal presentation, involving young males and older females. Ankle injuries play a major part in post multitrauma functional impairment t...
The ankle joint (also known as the tibiotalar joint or talocrural joint) forms the articulation between the foot and the leg. It is a primary hinge synovial joint lined with hyaline cartilage.
The ankle joint is comprised of the tibia, fibula and talus as well as the supporting l...
Ankle lateral view is part of a three view ankle series; this projection is used to assess the distal tibia and fibula, talus, navicular, cuboid, the base of the 5th metatarsal and calcaneus.
patient is in a lateral recumbent position on the table
the lateral aspect of the kn...
Ankle AP mortise view is part of a three view series of the distal tibia, distal fibula, talus and proximal metatarsals. It is the most pertinent projection for assessing the articulation of the tibial plafond and two malleoli with the talar dome, otherwise known as the mortise joint of the ankl...
The ankle radiograph checklist is just one of the many pathology checklists that can be used when reporting to ensure that you always actively exclude pathology that is commonly missed; this is particularly helpful in the examination setting, e.g. the FRCR 2B rapid-reporting.
The ankle series is comprised of an anteroposterior (AP), mortise and lateral radiograph. The series is often used in emergency departments to evaluate the distal tibia, distal fibula, and the talus; forming the ankle joint.
See approach to an ankle series.
Ankle radiographs are p...
Ankle teardrop sign is one of the radiological signs of an ankle joint effusion. It represents the presence of fluid in the inferior part of the anterior compartment of ankle.
This is a basic article for medical students and other non-radiologists
An ankle x-ray, also known as ankle series or ankle radiograph, is a set of two x-rays of the ankle joint. It is performed to look for evidence of injury (or pathology) affecting the ankle, often after trauma.
Ankylosing spondylitis (less commonly known as Bechterew disease and Marie Strümpell disease) is a seronegative spondyloarthropathy, which, as the name suggests, results in fusion (ankylosis) of the spine and sacroiliac (SI) joints, although involvement is also seen in large and small joints.
Thoracic manifestations of ankylosing spondylitis can be varied. For a general discussion of the condition refer to the parent article on ankylosing spondylitis.
It can affect the tracheobronchial tree and the lung parenchyma, and the disease spectrum includes:
upper lobe fibrocystic changes -...
Annular fissures are a degenerative deficiency of one or more layers that make up the annulus fibrosus of the intervertebral disc.
Many authors prefer the term annular fissure over annular tear, as the latter seems to imply acute injury 1,2. In the setting of severe trauma with di...
The annulus fibrosus surrounds the nucleus polposus and together they form the intervertebral disc.
The annulus comprises 15 to 20 collagenous (type I) laminae which run obliquely from the edge of one vertebra down to the edge of the vertebra below. The direction of the fibres al...
Anorexia nervosa is a psychiatric disorder characterised by distorted self-perception of body weight leading to starvation, obsession with remaining underweight, and an excessive fear of gaining weight. One in five patients with anorexia dies, due to complications of the disease.
The anteater nose sign refers to an anterior tubular elongation of the superior calcaneus which approaches or overlaps the navicular on a lateral radiograph of the foot. This fancifully resembles the nose of an anteater and is indicative of calcaneonavicular coalition 1,2.
History and etymolog...
The anterior abdominal wall forms the anterior limit of the abdominal viscera and is defined superiorly by the xiphoid process of the sternum and costal cartilages and inferiorly by the iliac crest and pubic bones of the pelvis.
The anterior abdominal wall has seven layers (from ...
Anterior angulation of the coccyx may be a normal variant but poses a diagnostic challenge for those considering coccygeal trauma.
Four types of coccyx have been described:
type I: the coccyx is curved slightly forward, with its apex pointing caudally (~70%)
type II: the coccy...
Anterior ankle impingement (AAI) syndrome is the result of chronic repetitive trauma with impingement of the anterior tibia against the talus.
Clinical features of anterior ankle impingement syndrome include painful and limited dorsiflexion and anterior joint line swellin...
A mnemonic that refers to the order of the ankle tendons that pass under the extensor retinaculum of the ankle running from medial to lateral is:
Tom Hates Dick
T: tibialis anterior
H: extensor hallucis longus
D: extensor digitorum longus
History and etymology
The phrase Tom, Di...
The anterior compartment of the arm is one of the two compartments of the arm.
A sheath of deep fascia surrounds the arm, the brachial fascia. Two intermuscular septa (medial and lateral) extend from it to attach to the humerus at the medial condylar ridge and lateral supracondylar ridge, respe...
The forearm is divided into the anterior compartment and the posterior compartment by the deep fascia, lateral intermuscular septum and the interosseous membrane between the ulna and radius.
The eight muscles located in the anterior compartment of the forearm can be divided into three...
The anterior compartment of the leg is one of the four compartments in the leg between the knee and foot. Muscles within this compartment primarily produce ankle dorsiflexion and toe extension.
The leg is separated into anterior, lateral, superficial posterior and deep posterior compartments by...
The anterior compartment of the thigh is one of the three compartments in the thigh. Muscles within this compartment primarily produce hip flexion and knee extension.
The thigh is separated into anterior, posterior and medial (adductor) compartments by intermuscular septa and surrounded by the ...
Anterior cruciate ligament (ACL) is one of the two cruciate ligaments that stabilise the knee joint.
The ACL arises from the anteromedial aspect of the intercondylar area on the tibial plateau and passes upwards and backwards to attach to the posteromedial aspect of the lateral ...
Anterior cruciate ligament (ACL) avulsion fracture or tibial eminence avulsion fracture is a type of avulsion fracture of the knee. This typically involves separation of the tibial attachment of the ACL to variable degrees. Separation at the femoral attachment is rare 5.
It is mor...
Anterior cruciate ligament (ACL) ganglion cysts, commonly referred to simply as ACL cysts, along with ganglion cysts arising from the alar folds that cover the infrapatellar fat pad, make up the vast majority of intra-articular ganglion cysts of the knee.
Anterior cruciate ligamen...
Anterior cruciate ligament (ACL) mucoid degeneration, along with tears and anterior cruciate ligament ganglion cysts, is a relatively common cause of increased signal within the anterior cruciate ligament (ACL). The appearance can mimic acute or chronic interstitial partial tears of the ACL. How...
Anterior cruciate ligament (ACL) tears are the most common knee ligament injury encountered in radiology practice.
The ACL is the most commonly disrupted ligament of the knee, especially in athletes who participate in sports that involve rapid starting, stopping, and pivoting (e.g. s...
Anterior hip dislocation is much less common than a posterior hip dislocation. It constitutes for only 5-18% of all hip dislocations.
While the posterior dislocation is often associated with fractures, the anterior dislocation is mostly an isolated injury 1.
It can be clas...
Anterior glenolabral injuries are common in the setting of anterior shoulder dislocation and comprise a number of closely related entities.
bony Bankart lesion
anterior labroligamentous periosteal sleeve avulsion (ALPSA)
glenolabral articular disruption (GLAD)
Causes of anterior hip pain include:
pigmented villonodular synovitis (PVNS)
inflammatory arthropathy (e.g. rheumatoid arthritis)
The anterior humeral circumflex artery is a vessel arising from the axillary artery at the proximal part of the arm. It is smaller in size relative to the posterior humeral circumflex artery.
origin: branch of the axillary artery at the proximal part of the arm
location: proximal arm...
The anterior humeral line is key to demonstrating normal elbow alignment and should be used whenever reading a paediatric elbow radiograph to exclude a subtle supracondylar fracture.
A line drawn down the anterior surface of the humerus should intersect the middle third of the capitel...
The anterior inferior iliac spine (AIIS) is bony prominence on the anterior border of the ilium forming the superior border of the acetabulum.
Attachments include the Iliacus, origin of straight head of the rectus femoris, and also the the proximal ileofemoral ligament (Y-ligament or ligament o...
Anterior inferior iliac spine (AIIS) avulsion injuries are one of the six main types of pelvic apophyseal avulsion fractures.
As with many pelvic avulsion injuries, they most often occur in adolescents (mostly between the ages 14-17). There is a slight male predilection and they ...
The anterior interosseous nerve also known as the volar interosseous nerve arises from the median nerve in the forearm, and supplies the flexor pollicis longus, pronator quadratus and the lateral portion of flexor digitorum profundus.
The anterior interosseous nerve conti...
Anterior interosseous nerve syndrome (AINS), also known as Kiloh-Nevin syndrome, is one of three common median nerve entrapment syndromes; the other two being pronator teres syndrome and the far more common carpal tunnel syndrome.
AINS is a rare entrapment syndrome, with comparati...
There are three anterior knee fat pads 1:
infrapatellar fat pad (of Hoffa)
fills the space between the patella ligament and the anterior intercondylar area of the tibia 2
posterior suprapatellar (prefemoral or supratrochlear) fat pad
anterior suprapatellar (quadriceps) fat pad
fills the spa...
Anterior knee pain is common with a variety of causes including:
inflammatory and depositional arthritis
bursitis around the knee
excessive lateral pressure syndrome (ELPS)
patellar cartilage defect
An anterior labroligamentous periosteal sleeve avulsion (ALPSA) lesion is similar to a Bankart lesion, in that it too is usually due to anterior shoulder dislocation and involves the anterior inferior labrum.
Unlike the Bankart lesion in which the labrum and glenoid periosteum is avulsed from ...
The anterior lateral malleolar artery is the counterpart to the anterior medial malleolar artery, supplies the lateral aspect of the ankle.
Origin and course
branch of anterior tibial artery
runs posterior to the tendons of extensor digitorum longus and fibularis tertius to th...
The anterior longitudinal ligament (ALL) runs along the anterior surface of the vertebral bodies (firmly united to the periosteum) and intervertebral discs (attaching to the anterior annulus). It ascends from the anterosuperior portion of the sacrum inferiorly to the become the anterior atlanto-...
Anterior medial malleolar artery is the counterpart to the anterior lateral malleolar artery, and supplies the medial aspect of the ankle.
Origin and course
branch of anterior tibial artery
arises approximately 5 cm proximal to the ankle
passes posterior to the tendons of exte...
The anterior capsular insertion, unlike the posterior aspect of the shoulder joint capsule which has a constant scapular attachment along the margins of the glenoid labrum, inserts a variable distance from the labrum.
The capsular insertions are classified as follows:
type I: at or very near t...
Anterior shoulder dislocation is by far the commonest type of dislocation and usually results from forced abduction, external rotation and extension 1.
Broadly speaking, anterior shoulder dislocations occur in a bimodal age distribution. The first, and by far the more prevalent a...
Anterior subluxation of cervical spine (also known as hyperflexion sprain) is a ligamentous injury to the cervical spine.
Patient presents with neck pain. There may be symptoms due to spinal cord oedema.
It results from ligamentous injury, however, there may b...
The anterior superior iliac spine is an important bony surface landmark and is the prominence is the most anterior part of the ilium. It can be palpated at the lateral end of the inguinal fold. Attachments include the inguinal ligament, tensor fasciae latae and sartorius.
Clinically, as an easi...
Anterior superior iliac spine (ASIS) avulsion injuries typically occur in athletes during forceful muscular contraction. ASIS is the site of attachment for sartorius and tensor fascia latae muscles.
ASIS avulsion, like other pelvic avulsion injuries, is a stable fracture.
The anterior talofibular ligament (ATFL) is part of the lateral collateral ligament complex of the ankle. Its role is to stabilise the talus. It is also the weakest of the lateral collateral ankle ligaments.
The ATFL is an intracapsular flat two-banded ligament that arises from ...
Anterior talofibular ligament (ATFL) injury is the most common of the ligament injuries that can occur as part of the lateral ligament complex injuries 2. The injuries can comprise either soft tissue tears, avulsion fractures or both.
ATFL injuries typically occur with an inversion i...
The anterior tibial translocation sign or anterior drawer sign (a.k.a. anterior translation of tibia) is seen in cases of complete rupture of the anterior cruciate ligament, and refers to anterior translocation (anterior tibial subluxation) of the tibia relative to the femur of more than 7 mm 1.
The anterior tibial veins, continuations of the venae comitantes of the dorsalis pedis artery, leave the anterior compartment between the tibia and fibula and pass through the proximal end of the interosseous membrane. They unite with the posterior tibial veins to form the popliteal vein at the ...
The anterolateral ligament of the knee (ALL) is a ligament that is thought to aid with rotational stability of the knee joint. Some think that its presence (or reconstruction) may result in better outcomes from ACL stabilisation surgery 2. The ligament has also been implied in Segond fractures 3...
The term anterolisthesis refers to anterior displacement (forward slip) of vertebral body relative to one below.
Implanted antibiotic beads are a form of microbiological treatment inserted during orthopaedic procedures to aid with the treatment of chronic infection. They are also used as a local treatment for osteomyelitis.
The beads are radiopaque, thus lending themselves to visualisation on all imaging ...
Antley-Bixler syndrome (ABS) (or trapezoidocephaly-synostosis syndrome) is a rare, autosomal dominant or recessive condition characterised by craniosynostosis and extra-cranial synostoses. Mid-facial hypoplasia is also common.
Very rare condition with only 50 cases described in th...
The AO classification of proximal humeral fractures, along with the Neer classification, is one of the most frequently used systems for classifying proximal humeral fractures.
The AO classification divides proximal humeral fractures into three groups, A, B and C, each with subgroups, and place...
The AO classification of sacral injuries aims to simplify and universalise the process of classifying sacral injuries and improve interobserver and intraobserver reliability.
The AO sacral classification is broken into three subsections that follow a hierarchical structure similar to the AO cla...
The AO classification of subaxial injuries aims to simplify and universalise the classification of subaxial cervical spine fractures and improve interobserver and intraobserver reliability.
The AO subaxial cervical spine injury classification involves four criteria based on morphology, facet in...
Apert syndrome (also known as type I acrocephalosyndactyly) is a syndrome that is predominantly characterised by skull and limb malformations.
The estimated incidence is at 1:65-80,000 pregnancies.
Thought to occur from a defect on the fibroblast growth factor receptor...
Apophyseal avulsion fractures of the pelvis and hip are relatively common among physically active adolescents and young adults.
Pelvic and hip apophyseal injuries typically occur in the 14 to 25 year age range.
Kicking sports, such as soccer, and gymnastics are frequen...
The apophyses (singular: apophysis) are the normal bony outgrowths that arise from separate ossification centres and eventually fuse with the bone in time. The apophysis is a site of tendon or ligament attachment, as compared to the epiphysis which contributes to a joint.
When unfused, they can...
The apophysis of the proximal 5th metatarsal lies laterally and is oriented longitudinally parallel to the shaft.
Apophysis of the fifth metatarsal base appears on plain radiographs at age 12 for boys and 10 for girls. Fusion of the apophysis to the metatarsal base usually occurs within the fol...
This is a basic article for medical students and other non-radiologists
Appendicular films are x-rays taken of the bones and joints of the arms and legs. I've used this term to separate the x-rays taken as part of an assessment of non-acute disease from trauma films which represent x-rays taken...
The appendicular skeleton is the portion of the bony skeleton that includes and supports the limbs (the appendages). It includes the pectoral girdle and the bony pelvis, connected to the axial skeleton centrally and is composed of 126 bones in total.
Appendicular bones form from cartilage, by ...
The apple core sign has been used to describe the circumferential erosion of the femoral neck seen in synovial chondromatosis. Although this is the most common process that may lead to an apple core erosion of the femoral neck, this has also been observed with:
pigmented villonodular synovitis
The arcade of Frohse (pronounced "\ Frəʊs \" to rhyme with "crows") is also known as the supinator arch.
The arcade is formed by a fibrous band between the two heads of the supinator muscle. The deep branch of the radial nerve passes beneath the arcade accompanied by vessels known as the leash ...
The arcuate foramen (foramen arcuale atlantis, ponticulus posticus or posterior ponticle, or Kimerle anomaly) is a frequently encountered normal variant of the atlas and is easily appreciated on a lateral plain film of the cranio-cervical junction.
It develops by calcification of the posterior ...
The arcuate ligament is part of the posterolateral ligamentous complex of the knee that is variably present, being found in ~65% (range 47.9-71%) of knees. It is a Y-shaped thickening of the posterolateral capsule, which arises from the fibular styloid and divides into two limbs:
medial limb: c...
The arcuate line is located at roughly one-third of the distance from the pubic crest to the umbilicus. It is the demarcation where the internal oblique and transversus abdominis aponeuroses of the rectus sheath start to pass anteriorly to the rectus abdominis muscle, leaving only the transversa...
The arcuate sign is often a subtle but important finding on knee x-rays and represents an avulsion fracture of the proximal fibula at the site of insertion of the arcuate ligament complex, and is usually associated with cruciate ligament injury (~90% of cases) 2. The fracture fragment is attache...
The arm is part of the upper limb below the pectoral girdle and above the forearm, comprising the humerus.
The elbow joint is inferior and the glenohumeral joint is superior. Arm flexion, extension, abduction, adduction, internal rotation and external rotation occur at the shoulder.
Arnold-Hilgartner classification is a plain radiograph grading system for haemophilic arthropathy of the knee 1,2:
stage 0: normal joint
stage I: no skeletal abnormalities, soft-tissue swelling is present
stage II: osteoporosis and overgrowth of the epiphysis, no cysts, no narrowing of the ca...
Arrested pneumatisation of the skull base is an anatomical variant that most commonly occurs in association with the sphenoid sinus. It is known that the sphenoid bones undergo early fatty marrow conversion antecedent to normal pneumatisation. However, for unclear reasons, some individuals exper...
Arthrofibrosis is a complication of injury or trauma to a joint. It can also be iatrogenic e.g. post knee surgeries. It consists of excessive scar tissue formation within the joint capsule, resulting in pain, stiffness, and swelling, that are greater than expected in the given clinical scenario....
Arthrogryposis (multiplex congenita) is a clinical or imaging descriptor that denotes congenital non-progressive joint contractures involving two or more body regions.
It is thought to occur in approximately 1:3000-10,000 live births 6,8.
It can result from a number o...
An easy to remember mnemonic for the causes of articular cartilage calcification is:
W: Wilson disease
The articularis cubiti is a muscle in the posterior compartment of the arm:
origin: posterior surface of the distal humerus
insertion: posterior surface of the elbow joint capsule
innervation: radial nerve
action: tenses the posterior elbow joint capsule during elbow extension
The articularis genu is a small flat muscle of the anterior knee. During knee extension it acts to tighten the synovial membrane superiorly thereby preventing impingement of the synovial folds between the femur and the patella.
origin: anterior distal femoral shaft
insertion: knee joi...
Aseptic loosening is considered relatively common complication of hip joint replacements. It is usually considered a long-term complication and is often considered as the most common complication 3.
Aseptic loosening can occur as a result of inadequate initial fixation, mechanical lo...
The American Spinal Injury Association (ASIA) was developed by the American Spinal Injury Association in 2006, and at the time of writing (July 2016), remains the most widely used scale.
This scale is part of the ASIA spinal cord injury classification. It divides spinal cord injuries into 5 cat...
Asphyxiating thoracic dysplasia, also known as Jeune syndrome, is a type of rare short limb skeletal dysplasia, which is primarily characterised by a constricted long narrow thoracic cavity, cystic renal dysplasia and characteristic skeletal features. It is also sometimes classified as one of th...