≤11 ribs is associated with a number of congenital abnormalities and skeletal dysplasias, including:
Down syndrome (trisomy 21)
asphyxiating thoracic dysplasia (Jeune syndrome)
short rib polydactyly syndromes
chromosome 1q21.1 deletion...
Achilles tendon thickening can occur for a number of reasons.
The Achilles tendon has an average AP diameter of 6 mm 1. Thickening of the tendon is when it exceeds 8 mm in AP diameter and can result from:
Acro-osteolysis (plural: acro-osteolyses) refers to resorption of the distal phalanx. The terminal tuft is most commonly affected. It is associated with a heterogeneous group of pathological entities and, some of which can be remembered by using the mnemonic PINCH FO.
When there is linear bone ...
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
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
Benign lytic bone lesions encompass a wide variety of entities. A useful starting point is the FEGNOMASHIC mnemonic.
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Conditions associated with bone deformity from softening includes:
bowing of long bones
biconcave vertebral bodies / codfish vertebra
There are several bony lesions that can involve or produce a sequestrum.
Brodie abscess: osteomyelitis
certain soft tissue tumors (with bony extension)
malignant fibrous histiocytoma
metastasis (especially from breast ca...
Bone mineral density (BMD) is defined as the amount of mineral (calcium hydroxyapatite) per unit of bone.
BMD can be measured by various methods with DEXA the most prevalent
gamma rays: replaced by radiographic methods
single-energy photon absorptiometry (SPA) was super...
Bone within a bone is a descriptive term applied to bones that appear to have another bone within them. There are numerous causes including:
thoracic and lumbar vertebrae (neonates and infants)
growth recovery lines (after infancy)
cortical splitting and new periostitis
sickle cell d...
Bridging (or fusion) of the pubic symphysis can be associated with various systemic and local causes, including 1-3:
Carpal angle is defined by two intersecting lines, one in contact with the proximal surface of the scaphoid and the lunate and the other line through the proximal margins of the triquetrum and the lunate. Its normal value is between 130° and 137°.
It is increased (>139°) in:
The differential for cartilaginous lesions includes:
There are several important causes of an abnormal lunate signal on MRI, the most frequent causes being Kienbock disease (25%), ulnar impaction syndrome (25%) and intraosseous ganglia (20%).1 Appreciation of the pattern of bone signal change can often allow the correct diagnosis to be made.
Cervical spine injuries can involve the cervical vertebral column, intervertebral discs and cervical spine ligaments, and/or cervical spinal cord. The cervical spine accounts for ~50% of all spinal injuries.
5-10% of patients with blunt trauma have a cervical spine injury 1.
Chondrocalcinosis (plural: chondrocalcinoses) is a descriptive term indicating the presence of gross calcium deposition within articular cartilage, i.e. both hyaline and fibrocartilage.
Chondrocalcinosis articularis was an early term for calcium pyrophosphate dihydrate deposition d...
Clavicle tumors may be malignant or benign.
osteoma: uncommon, sclerotic, hamartomatous surface lesion
enchondroma: rare, geographic, intramedu...
A Codman triangle is a type of periosteal reaction seen with aggressive bone lesions. The periosteum does not have time to ossify with shells of new bone (e.g. as seen in a single layer and multilayered periosteal reaction) in aggressive lesions, so only the edge of the raised periosteum will os...
Companion shadows are smooth, homogeneous, radiopaque shadows running parallel along the bones. In a study of 700 chest radiographs, Ben Felson found that 75% had companion shadows on the lower ribs 3.
They appear secondary to soft tissues and intercostal muscles running ...
Complications of total hip arthroplasty are common and it is essential for the radiologist to be aware of them in the assessment of radiographs of total hip replacements. Complications are many and can occur at various time intervals following the initial surgery:
aseptic loosening: considered ...
There are many conditions that can involve both skin and bone.
osteolytic bone lesions
basal cell nevus syndrome
langerhans cell histiocytosis
Congenital limb amputation is the absence of a fetal limb or part of a limb that usually occurs due to disruption of vascular supply.
Congenital amputations occur in 0.5 (range 0.03-1) per 1000 live births 2.
They are slightly more common in the upper limb (60%) than ...
Coronal vertebral clefts refer to the presence of radiolucent vertical defects on a lateral radiograph.
It is most often seen in premature male infants 1,3. As they can occur as part of normal variation (especially in the lower thoracic-upper lumbar spine of premature infants) t...
Craniovertebral junction (CVJ) anomalies can be congenital, developmental or due to malformation secondary to any acquired disease process. These anomalies can lead to cranial nerve compression, vertebral artery compression and obstructive hydrocephalus.
The craniovertebral junction ...
The musculoskeletal manifestations of cystic fibrosis are uncommon compared to the well known respiratory manifestations.
For general discussion of cystic fibrosis, and a discussion of its other manifestations, please refer to:
cystic fibrosis (parent article)
pulmonary manifestations of cys...
There is broad differential for cyst-like lesions around the knee.
popliteal synovial cyst - Baker cyst
intra-articular ganglion cyst
ACL ganglion cyst
PCL ganglion cyst
Hoffa fat pad ganglion cyst
extra-articular ganglion cyst
A generalized retardation in skeletal maturation has different causative or etiological factors, these can be classified as follows:
chronic ill health
congenital heart disease (especially cyanotic)
chronic renal disease
inflammatory bowel disease
malnutrition: failure to thrive (FTT)
The differential diagnosis for a dense base of the skull includes:
Van Buchem disease
The differential diagnosis of dense metaphyseal bands is wide.
chronic anemia, e.g. sickle cell disease, thalassemia
chemotherapy, e.g. methotrexate
growth acceleration lines following growth arrest due to systemic illness or stress in infancy or childhood, e.g...
Diaphragmatic paralysis (also considered very similar to the term diaphragmatic palsy) can be unilateral or bilateral.
Clinical features are highly variable according to underlying etiological factor:
unilateral paralysis: asymptomatic in most of the patients as the othe...
Diaphyseal lesions are unsurprisingly predominantly found centered in the diaphysis.
simple bone cyst
myeloma / plasmacytoma
round cell tumor, e.g. Ewing sarcoma (children)
Forefoot pain in the metatarsal region is a common complaint and may be caused by a number of conditions. It is worthwhile for a radiologist to have knowledge of the potential causes and their imaging features 1.
plantar plate disruption
A diffuse homogeneous bone marrow FDG uptake usually reflects hyperplastic bone marrow which can be seen in the following conditions:
granulocyte colony-stimulating factor (G-CSF)
Diffuse T1 vertebral bone marrow signal loss is associated with replacement of fatty marrow by edema or cellular tissue. T1-weighted imaging without fat suppression is one of the most important sequences for distinguishing between normal and abnormal bone marrow. In the case of homogenous involv...
Disorganized or complex periosteal reaction has spicules with random orientation and appearance. It can be seen in highly aggressive processes:
malignant fibrous histiocytoma
spindle cell sarcoma
Erosion or absence of the distal ends of the clavicles may be seen in a wide range of conditions.
weightlifter's shoulder: due to repetitive microtrauma; classically described in weightlifters, but can affect anyone performing repetitive overhead lift...
Dystrophic soft tissue calcification is a type of soft-tissue calcification, which occurs in damaged or necrotic tissue, while the serum level is normal. It may progess to ossification, in which case a cortical and trabecular bone pattern is visible.
An often cited approach to developing a diff...
Elbow arthroplasties are an increasingly common joint replacement, most often used for treatment of late stage rheumatoid arthritis, but which may also be used as a treatment for late stage osteoarthritis or complex fractures of the proximal radius, proximal ulna, or distal humerus.
Empyemas are purulent inflammatory collections within a body cavity. Contrast this with abscesses, which arise within parenchymal tissue, rather than occupying a pre-existing anatomical space.
Colloquially, the standalone term empyema is used to refer to thoracic empyemas but there...
Endosteal scalloping refers to the focal resorption of the inner layer of the cortex (i.e. the endosteum) of bones, most typically long bones, due to slow-growing medullary lesions.
It is important to note that although it is evidence of a slow non-infiltrative lesion, it does not equate to ben...
Epiphyseal lesions comprise tumors and other pathologies that occur around the epiphysis and any epiphyseal equivalent bone.
Common differential diagnoses include 2-4:
chondroblastoma: rare epiphyseal tumor found in young adults; it usually does not extend into the meta...
There are numerous eponymous fractures which are named after the people who first described their existence (but see Stigler's law of eponymy) 1:
Bankart fracture: glenoid
Barton fracture: wrist
Bennett fracture: thumb
Bosworth fracture: ankle
Chance fracture: vertebral
Charcot joint: foot...
Erlenmeyer flask deformity (EFD) (also known as metaphyseal flaring) refers to a radiographic appearance typically on a femoral radiograph demonstrating relative constriction of the diaphysis and flaring of the metaphysis.
It has been classically used with reference to the distal ends of the fe...
Differential diagnosis of erosion of the superior aspects of the ribs include:
Erosion of the odontoid peg can result from a number of pathological entities:
rheumatoid arthritis: classic 1,2
systemic lupus erythematosus
calcium pyrophosphate arthropathy (CPPD): relatively common
non-inflammatory arthropathy: osteoar...
Erosive arthritis has a broad differential:
clinically an acute inflammatory attacks (swelling, erythema, pain) in postmenopausal woman
typically includes the distal interphalangeal joints, proximal interphalangeal joints, 1st carpometacarpal joint 6, but not the metaca...
Exostoses are defined as benign growths of bone extending outwards from the surface of a bone. It can occur in any bone and be triggered by a number of factors. There are a number of examples of exostoses that occur due to local irritant stimuli:
exostosis of the external audit...
Expansile lytic bone lesions without cortical destruction can result from various benign and malignant neoplastic pathologies, causes include 1:
unicameral bone cyst
aneurysmal bone cyst (eccentric)
chondromyxoid fibroma (eccentric)
non-ossifying fibroma (eccentric)
Extensor mechanism of the knee injuries include:
quadriceps muscle tears
quadriceps tendon rupture
patellar tendon rupture
patellar dislocation often with medial retinaculum tears
patellar sleeve fractures
Knowing extraskeletal musculoskeletal lesions by compartment is useful to help generate a meaningful differential diagnosis:
extraskeletal myxoid chondrosarcoma
Fall onto an outstretched hand (FOOSH) is a common mechanism for wrist-forearm fractures, in certain cases with involvement of elbow structures, particularly in children.
Some injuries that result from such a fall include:
Fetal rib fractures can be caused by certain skeletal dysplasias. These include:
osteogenesis imperfecta: type II - one of the classical causes of fetal rib fractures
achondrogenesis: type Ia - Houston-Harris sub type
Fibromatosis refers to a wide range of soft tissue lesions that share an underlying histopathologic pattern of fibrous tissue proliferation. They can occur in a variety of anatomic sites (e.g. musculoskeletal, abdominopelvic, breast, etc.) and also vary in their behavior, ranging from indolent/b...
The differential for fibrous lesions is wide and includes:
osteofibrous dysplasia / adamantinoma
malignant fibrous histiocytoma / fibrosarcoma
Floating meniscus (also known as meniscal avulsion) occurs in acute traumatic settings when the meniscotibial coronary ligaments get disrupted leading to avulsion of the meniscus from the tibial plateau.
Displacement of the meniscus for 5 mm or more from the tibial p...
Flowing ossifications are seen in diffuse idiopathic skeletal hyperostosis (DISH).They are defined as heterotopic ossifications involving the anterior longitudinal ligament, paraspinal connective tissues and annulus fibrosus of at least four contiguous vertebral bodies and are originally describ...
Fluid-fluid level containing bone lesions are best seen on MRI, although with narrow window width they can also be appreciated on CT.
Their prevalence is estimated at ~3% of bone and soft tissue tumors 1.
Their presence is non-specific, as they are seen in...
Fracture-dislocations of the radius and ulna illustrate the importance of including the joint above and below the site of injury on radiographic assessment.
Most forearm fractures (60%) include fracture of the distal radius as well as an ulnar fracture. In some cases, there is associated disloc...
Fractures of the thumb are important due to huge impact the thumb has on the overall function of the hand, an understanding of the types of fractures that occur is important, as treatment varies with fracture type.
Metacarpal fractures include:
Frontal bossing is a calvarial radiographic feature where the front of the skull appears protruding anteriorly. It is best appreciated on a sagittal or lateral image.
This feature can be seen in many conditions (in alphabetical order):
The causes of generalized increase in bone density in adult patients, also known as generalized or diffuse osteosclerosis, can be divided according to broad categories:
marrow cavity is narrowed by endosteal new bone
patchy lucencies due to the persist...
The causes of generalized increased bone density in pediatric patients can be divided according to a broad category of causes:
dense metaphyseal bands
cortex and flat bones may also be slight...
Generalized osteopenia refers to osteopenia diffusely affecting the bones.
The differential diagnosis is wide and includes:
osteoporosis: decreased osteoid production
osteomalacia: undermineralisation of osteoid
The list of causes of a generalized periosteal reaction overlaps that of symmetrical periosteal reaction, and includes 1,2:
vascular stasis (common)
infantile cortical hyp...
A gibbus deformity is a short-segment structural thoracolumbar kyphosis resulting in sharp angulation.
There are a number of causes which can be divided into congenital and acquired.
cretinism (congenital hypothyroidism)
Gracile bones refer to changes in the skeleton in which the bones are more slender than usual (over-tubulated) and occasionally deformed in other ways such as being abnormally curved. This may occur in a number of disorders and can occur with or without fractures.
A high bone mineral density is one where the bone mineral density (BMD) is usually greater than two standard deviations above what is expected for age. This can sometimes be seen on routine DXA scan assessment. Some authors advocate a definition of a high BMD where the Z-score is >+2.5 to highli...
A high-riding shoulder refers to the superior displacement/subluxation of the humeral head with resultant decrease in the acromiohumeral distance.
The differential for a high-riding shoulder is:
rotator cuff tear with or without rotator cuff arthropathy
Musculoskeletal manifestations of HIV/AIDS are not as common as CNS or pulmonary complications. Nonetheless, their prevalence is high.
Depending on the condition, etiology may be related to the HIV infection itself, the resultant immunodeficiency, or antiretroviral therapy (HAART).
Hydroxyapatite crystal deposition disease (HADD) is a disease of uncertain etiology characterized by periarticular and intra-articular deposition of hydroxyapatite (HA) crystals.
The shoulder is the most frequently involved site with classic calcific tendinitis presentation.
Hyperostosis of the skull has many causes, broadly divided into focal or diffuse.
Paget disease of bone
metastatic disease, especially prostate carcinoma
chronic, severe anemia
hyperostosis frontalis interna
long-term phenytoin use
Hypertrophic osteoarthropathy (HPOA) is a syndrome characterized by periosteal reaction of the long bones without underlying bone lesion. There are a broad range of manifestations, although typically there is symmetrical involvement of the appendicular skeleton. Accompanying abnormal soft tissue...
A generalized acceleration in bone maturation can result from a number of etiological factors. They include:
idiopathic isosexual precocious puberty
hypothalamic or parathalamic lesion with sexual precocity: e.g.
A mnemonic that can be used to remember the causes of increased heel pad thickness is:
D: phenytoin therapy
P: peripheral edema
Intervertebral disc calcification is a non-specific finding seen in numerous conditions.
It may be observed in pediatric 5 as well as adult populations.
degenerative: relatively common and may occur in up to 6% of routine abdominal radiographs in adults
Intra-articular gas or air (pneumarthrosis) can occur from a number of varied pathologies and should be interpreted according to the clinical context.
compound injury with gas entering from the outer surface
can occur in with a pneumolipohaemarthrosis
Joint ankylosis has a relatively broad differential including 1-5:
chronic reactive arthritis
juvenile idiopathic arthritis
surgical ankylosis (arthrodesis)
coalition, e.g. tarsal, c...
A J-shaped sella is a variant morphology of the sella turcica, whereby the tuberculum sellae is flattened, thus forming the straight edge of the "J". The dorsum sellae remains rounded and forms the loop of the "J".
Differential diagnosis for a J-shaped sella includes 1,2...
Juvenile osteoporosis refers to osteoporosis occurring in children.
It can arise from a number of causes 1-4:
osteoporosis pseudoglioma syndrome
Lead poisoning or plumbism is a multisystem condition due to the way in which lead interferes with the function of virtually every organ system. Plumbism most severely manifests due to its devastating effects on the CNS, but it also has important deleterious consequences on the skeletal, renal, ...
Leg bowing in children is common and often developmental.
The differential includes:
exaggeration of normal age-related angulation changes at the knee
neonates and infants normally have varus angulation that gradually corrects within 6 months of w...
Long bone metaphyseal cupping is most likely due to the local oligaemia from thrombosis in the terminal epiphyseal arteries to the epiphyseal plate, induced by prolonged regional immobilization 7.
The differential diagnosis of long bone metaphyseal cupping includes:
Loss of intervertebral disc space can be due to a variety of causes:
degenerative disc disease of the spine: most common cause
dialysis related spondyloarthropathy
crystal deposition diseases
Lytic bone metastases are due to a variety of primary tumors, and are more common than sclerotic metastases (although many may occasionally have mixed lytic and sclerotic components). They include 1:
renal cell cancer
adrenal gland carcinoma and pheochromocytoma
Lytic skull lesions have a relatively wide differential that can be narrowed, by considering if there are more than one lesion and whether the mandible is involved.
lytic skeletal metastases
epidermoid - scalloped border with a sclerotic rim
Here is a list of some of the most useful differential diagnoses in musculoskeletal imaging.
lucent/lytic bone lesions (FEGNOMASHIC)
multiple lucent/lytic bone lesions
benign lytic bone lesions in patients under 30 years old
diffuse bony sclerosis
permeative process in bone
There are many causes for mandibular periostitis:
Langerhans cell histiocytosis
malignancy (both primary and metastatic)
necrosis, e.g. radiation osteonecrosis
Garre's sclerosing osteomyelitis
March fractures are a name subtype of fatigue/stress fracture. They occur due to repeated concentrated trauma to a normal bone, classically the 2nd metatarsal of the foot but can occur in other weight-bearing bones of the lower limb and pelvis.
Please see the article on s...
Masticatory muscle hypertrophy or commonly presenting as temporalis and masseter muscles hypertrophy is a rare disease that affects muscles of mastication and results in "pseudo-masses". Commonly seen in anxious individuals with "bruxism" and in chronic gum chewing 1.
It sometimes gives a "thr...
Meary's angle or talus-first metatarsal angle has been used to identify the apex of deformity in patients with pes cavus and pes planus on lateral weight-bearing foot radiographs. It is the angle between a line drawn from the centers of longitudinal axes of the talus and the first metatarsal.
Medial epicondyle fractures represent almost all epicondyle fractures and occur when there is avulsion of the medial epicondyle. They are typically seen in children, and can be challenging to identify. Failure to diagnose these injuries can lead to significant long term disability.
Medial epicondylitis (also known as golfer's elbow) is an angiofibroblastic tendinosis of the common flexor- pronator tendon group of the elbow.
It is less common than lateral epicondylitis. As with lateral epicondylitis, it typically occurs in the 4th to 5th decades of life. Ther...
Medical devices in the abdomen and pelvis are important to be recognized, just like medical devices of the chest. Often we ignore these devices, considering them to be incidental and non-pathological, however it is essential to be aware of potential complications.