Adventitial bursae are those bursae that develop later in life in response to pressures developed as a result of acquired bony prominences or deformities 1. These bursa can become inflamed resulting in adventitious bursitis.
Adventitious or adventitial bursitis refers to inflammation associated with adventitious bursae.
Adventitious bursae are not permanent native bursae. They can develop in adulthood at sites where subcutaneous tissue becomes exposed to high pressure and friction.
Aggressive angiomyxomas are rare tumors that arise in the pelvis and typically cross the levator ani muscles. Despite its name, it is essentially a benign tumor and the term "aggressive" is given due to a predilection for local recurrence. Only rarely does it metastasize.
It is se...
Aggressive fibromatosis is a type of musculoskeletal fibromatosis. While it is a non-metastasizing fibrous lesion, it is thought to be a true neoplasm that arises from the fascial and musculoaponeurotic coverings, sometimes at the site of a traumatic or post-surgical scar.
Aggressive granulomatosis post hip replacement is a potential complication of a hip joint replacement. Some authors use the same term for particle disease - if you are an expert on this we would love your help.
Aggressive granulomas consist of well organized connective tissue contain...
Aggressive vertebral hemangiomata are a rare form of vertebral hemangiomata where significant vertebral expansion, extra-osseous component with epidural extension, disturbance of blood flow, and occasionally compression fractures can be present causing spinal cord and/or nerve root compression 1...
This classification was proposed by Ahlback et al. in 1968.
According to Ahlbäck system, knee joint osteoarthritis is classified as:
grade 1: joint space narrowing (less than 3 mm)
grade 2: joint space obliteration
grade 3: minor bone attrition (0-5 mm)
grade 4: moderate bone attrition (5-1...
Ainhum, also known as dactylolysis spontanea, is a rare cutaneous condition in which a hyperkeratotic band partially or totally encircles a digit. The constriction thins the underlying bone, which is then prone to fracture. Some cases result in autoamputation.
Some have suggested ...
Alar ligament calcification is rare. The alar ligaments arise bilaterally from the upper portion of the odontoid process and run obliquely cephalad and laterally to insert on the medial surface of the occipital condyles. They stabilize the head during rotatory movements.
Alban Köhler (1874-1947) was a German radiologist best known for both his work in describing avascular necrosis of the navicular (now known as Köhler disease) and the publication of ‘Roentgenology - The Borderlands of the Normal and Early Pathological in the Skiagram’ a textbook exploring anatom...
Allen and Ferguson classification is used for research purposes to classify subaxial spine injuries. It is based ofn the mechanism of injury and position of the neck during injury. This classification was proposed by Allen and Ferguson in 19823 and at the time of writing (July 2016) remains the ...
The alpha angle is a measurement used in the ultrasonographic assessment of developmental dysplasia of the hip (DDH).
The angle is formed by the acetabular roof to the vertical cortex of the ilium and thus reflects the depth of the bony acetabular roof. This is a similar measurement to the acet...
Alpha angle can refer to two different musculoskeletal measurements:
alpha angle (in developmental dysplasia of the hip) in children
alpha angle (in femoroacetabular impingement)
The alpha angle is a radiological measurement proposed for the diagnosis and evaluation of surgical treatment in cam-type femoroacetabular impingement (FAI).
When initially described in 2002, Notzli et al. suggested that the pathological value was >50°.
According to one study, a value measure...
Alternating radiolucent and radiodense metaphyseal lines can be seen with a number of conditions and the differential diagnosis is wide:
growth arrest lines
rickets: especially those on prolonged treatment, e.g. vitamin D dependent rickets
Alveolar rhabdomyosarcomas are a type of rhabdomyosarcoma and account for 20-40% of all rhabdomyosarcomas 1-2.
Unlike embryonal rhabdomyosarcomas, which are more common, these tumors occur in slightly older individuals, typically 10-25 years of age 1.
Alveolar soft part sarcomas (ASPS) are rare, highly vascular, deep soft tissue malignancy that is classically seen in the lower extremities of young adults. They account for <1% of all soft tissue sarcomas.
There is a slight female predilection in patients less than 30 years old 1...
The American Academy of Orthopedic Surgeons classification of periprosthetic hip fractures divides the femur into three separate regions:
level I: proximal femur distally to the lower extent of the lesser trochanter
level II: 10 cm of femur distal to level I
level III: femur distal to level...
Amniotic band syndrome (ABS) comprises of a wide spectrum of abnormalities, all of which result from entrapment of various fetal body parts in a disrupted amnion. Due to the randomness of entrapment, each affected individual has the potential to form a unique deficit.
Amphiarthroses are a functional class of joint that permit a small amount of movement under normal conditions.
symphyses (secondary cartilaginous joints)
The term amputation refers to the disconnection of all or part of a limb from the body. Specifically amputation is defined as removal of the structure through a bone. This is in contrast to disarticulation, which is removal of the structure through a joint.
When due to trauma, traumatic amputat...
The Amsterdam wrist rules are validated clinical decision rules for determining which patients require radiographic imaging (wrist radiography) for acute wrist pain following trauma. The initial study evaluated 882 patients and were published in 2015 1. The decision rules assessed different clin...
Amyloid arthropathy results from the extracellular deposition of the fibrous protein amyloid within the skeletal system and is a skeletal manifestation of amyloidosis particularly in patients on long term haemodialysis. It may involve either the axial skeleton (especially the cervical spine) or ...
Amyopathic dermatomyositis (ADM) is recognized as a distinct subtype of dermatomyositis where there is a typical skin rash of classic dermatomyosiytis but without muscle involvement.
This form may be further divided into
anti-melanoma differentiation-associated gene 5 (MDA5) antibo...
Amyoplasia congenita is a syndrome characterized by multiple specific congenital joint contractures, associated with substitution of muscular tissue by fibrosis and adipose tissue.
The estimated incidence is at 1: 10000 live births. There may be a higher prevalence with twin preg...
The anal sphincter is divided into an internal and external anal sphincter. It surrounds the anal canal.
Internal anal sphincter
continuation of inner rectal muscle
thickened, circular muscle fibers, up to 5 mm thick
composed of visceral muscle
External anal sphincter
An anaplastic rhabdomyosarcoma is a subtype of embryonal rhabdomyosarcoma, characterized by extensive anaplastic cells seen throughout the tumor 1.
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 epitrochlearis is an accessory muscle at the medial aspect of the elbow. It is also known as the accessory anconeus muscle or epitrochleoanconeus muscle and should not be confused with the anconeus muscle which is present at the lateral aspect of the elbow.
The anconeus muscle 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 epic...
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 spondylodiskitis 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 tumor-like bone lesions of uncertain etiology, 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 in...
Angiolipomas (also sometimes known as haemangiolipomas, vascular lipomas, and fibromyolipomas) are rare soft tissue tumors 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 tumor of bone. These are rare and account for less than 1% of malignant bone tumors. The majority of these tumors arising in bone are primary; however, a tiny percentage are either radiation-induced or associated with bone infarction
The angle of the longitudinal arch (calcaneal–fifth metatarsal angle) is one of the angles drawn on the weight-bearing lateral foot radiograph.
The angle is formed between the calcaneal inclination axis and a line drawn along the inferior edge of the 5th metatarsal:
pes planus: >170°
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 and foot radiography is the plain radiographic investigation of the distal tibia and fibula, the tarsal bones and metatarsals. Radiographic examination of the foot and ankle are often requested together, however, there is a plethora of literature to aid in the correct request of x-ray exam...
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 horizontal beam lateral view is a modified lateral view 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.
The horizontal beam lateral is a highly adaptable projectio...
There are several ankle impingement syndromes. They are characterized by limited range of motion and pain on attempting specific movements about the joint and often in a load-bearing position. They have variable etiology and pathogenesis. They are best classified according to location.
The key ...
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 (mortice is equally correct) 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 ...
Ankle radiographs are frequently performed in emergency departments, usually, after trauma, the radiographic series is comprised of three views: an anteroposterior, mortise, and a lateral. They may be performed to assess degenerative or inflammatory arthritis as well as to look for the sequela o...
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...
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 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 annular ligament can refer to:
annular ligament of the stapes
annular ligament of the proximal radio-ulnar joint
The annulus fibrosus (plural: annuli fibrosi) surrounds the nucleus pulposus 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 d...
Anorexia nervosa is a psychiatric disorder characterized 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 anterior ankle tendons around the ankle is:
Tom Hates Dick
The mnemonic can be used to remember the order of the tendons from medial to lateral as they pass under the extensor retinaculum of the ankle.
T: tibialis anterior
H: extensor hal...
The anterior center-edge angle, also known as the vertical-center-anterior (VCA) angle, is a radiographic measurement of the anterior coverage of the femoral head by the acetabulum. It is used in assessing acetabular dysplasia and pincer type of femoroacetabular impingement.
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 stabilize 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) reconstruction is a common procedure post ACL tear. It aims to reduce knee joint instability and thus prevent any further meniscal and/or cartilage damage.
There are numerous surgical techniques for ACL reconstruction 1-3:
Anterior cruciate ligament (ACL) reconstruction complications are common, occurring in 10-25% of patients.
Patients with complications of ACL reconstruction can present with decreased range of motion (impingement or arthrofibrosis) and/or laxity (graft rupture or stretchi...
Anterior cruciate ligament (ACL) tears are the most common knee ligament injury encountered in radiology and orthopedic practice.
Patients typically present with symptoms of knee instability, usually after acute trauma. The following signs and symptoms are common:
Anterior hip dislocation is much less common than a posterior hip dislocation. It constitutes 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 classifi...
The anterior or frontal fontanelle (or fontanel) is the diamond-shaped soft membranous gap at the junction of the coronal and sagittal sutures. It persists until approximately 18-24 months after birth, after which it is known as the bregma. The precise timing of the anterior fontanelle closure i...
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 pediatric 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 capit...
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 proximal ileofemoral ligament (Y-ligament or ligament of Bi...
Anterior inferior iliac spine (AIIS) avulsion injuries are one of the six main types of pelvic apophyseal avulsion fractures. Subacute or chronic avulsion injuries can be mistaken for a pseudotumor.
As with many pelvic avulsion injuries, they most often occur in adolescents (most...
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 which can be divided anatomically using a layered approach1 from superficial to deep:
Superficial soft tissues
quadriceps tendinosis / partial tear
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.
It is often the result of chronic injury rather than acute dislocation;...
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 superiorly 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 the cervical spine, also known as hyperflexion sprain, is a ligamentous injury of the cervical spine.
Patients present with severe, focal neck pain. There may be neurological symptoms due to spinal cord injury.
Anterior subluxation of t...
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, sartorius and depending on which resource you read, the ten...