Table 4

Pathology

TermDefinitionUltrasound appearanceCaveat
(A) Tendon
Tendinopathy9–12 A clinical term used to describe painful conditions of the tendon or tendon sheath including tendinosis, tendinitis and tendon tearThe use of a more precise term is recommended when describing imaging findings if possible.
Tendinosis9 11–14 A chronic tendon condition characterised histologically as collagen degeneration (predominantly mucoid) with other variable features such as collagen disorganisation, fibrocartilaginous metaplasia, calcification and possible neovascularity; primarily an overused and degenerative process with absence of an acute inflammatory infiltrate, but inflammatory mediators may be presentAbnormally hypoechoic tendon without tendon fibre disruption, with possible increase in tendon diameter, with or without flow on Doppler imaging (figure 2A)
Tendinitis9 11 12 Tendon inflammation.Abnormally hypoechoic tendon occasionally associated with possible increased flow on Doppler imagingImaging features of tendinosis and tendinitis are similar and may be difficult to differentiate. Features of tendinosis and tendinitis may be present concurrently. Hyperaemia, as seen in tendinosis, is due to neovascularity and should not be equated with acute inflammation. Clinical features (such as history of inflammatory disease) may be required to determine the most likely histological diagnosis.
Calcific tendinopathy15 16 Calcium deposition within a tendon; if calcium hydroxyapatite, this may be termed calcific tendinosis. Use calcific tendinitis when in the resorptive or inflammatory stage.Calcium hydroxyapatite appears as a globular well-defined hyperechoic focus within a tendon with variable shadowing. Overlap with other forms of calcification and crystal deposition are possible. Small punctate or linear tendon calcifications may also be due to calcium pyrophosphate dihydrate deposition disease or degenerative calcification. Amorphous echogenicity with variable shadowing can be seen with monosodium urate deposition in gout (figure 2B).
Tenosynovitis9 12 Inflammation of the tendon synovial sheathDistention of a tendon sheath from fluid of variable echogenicity with or without synovial hypertrophy and possible increased flow on Doppler imaging (figure 2C)Some tendon sheaths normally communicate with joints (ie, long head of the biceps brachii tendon sheath and glenohumeral joint, flexor hallucis longus tendon sheath and tibiotalar joint). Simple fluid within the tendon sheath may be secondary to intra-articular pathology rather than tenosynovitis.
Stenosing tenosynovitis9 12 17 18 A subtype of tenosynovitis that affects tendons that course through osteofibrous tunnels composed of bone covered by a pulley or retinaculum. The hallmark is thickening of the pulley or retinaculum that causes constriction. Examples include trigger finger and de Quervain tenosynovitis.Hypoechoic thickening of pulley or retinaculum with possible hyperaemia on Doppler imaging with possible additional findings of tendinosis and tenosynovitis (figure 2D)
Paratenonitis9 19–21 Inflammation and fibrosis of the paratenon surrounding a tendon that does not have a tenosynovial sheath (ie, the Achilles tendon)Focal or diffuse abnormal hypoechogenicity surrounding a tendon with possible increased flow on Doppler imaging (figure 2E)Several related terms have been described in the literature, including paratendonitis, peritenonitis and peritendinitis, paratenopathy, among others.
Tear22–25 Disruption of tendon, categorised as partial thickness (interstitial/intrasubstance, bursal or articular (if relevant)) or full thickness (focal or full width/complete); a longitudinal split tear may also be described, typically when involving a tubular tendon.Hypoechoic or anechoic tendon fibre disruption with an extent defined by the categories listed in the definition column. With longitudinal tears, the hypoechoic or anechoic abnormality is parallel to the long axis of the tendon (figure 2F).
AvulsionTendon tear at its bony attachment or a fracture at a tendon attachmentVariable depending on specific pathology (see other more precise terms)Due to a traction mechanism (as opposed to direct trauma)
(B) Muscle
Strain26 A clinical/biomechanical term which is not well defined and used inconsistently for different muscle injuriesGenerally, refers to an elongation or stretch type of injury
Tear26–31 Injury to muscle fibres or internal aponeurosesVariable, depending on degree of injury ranging from increased echogenicity of intact muscle to muscle or musculotendinous disruption (partial or complete) with possible haemorrhage of variable echogenicity. Possible increased flow on Doppler imaging (figure 3A.1,A.2)Numerous clinical and imaging-based classification and grading systems for muscle injury exist.
Contusion27–29 Muscle injury with or without haematoma most commonly as a result of blunt traumaMixed echogenicity area of muscle fibre disruption ranging from hyperechoic when acute to anechoic when chronic with possible mass effect from haematoma, possible increased flow on Doppler imaging (figure 3B)
Myositis ossificans27 32 33 A subtype of heterotopic ossification located within muscle most commonly occurring after trauma, often preceded by haematomaHyperechoic in early phase followed by a hypoechoic mass-like area within muscle, with hyperechoic foci maturing into an echogenic peripheral rim with possible acoustic shadowing. Possible increased flow on Doppler imaging (figure 3C)Radiograph or CT scan may be required to confirm the peripheral mineralisation when shadowing does not allow accurate characterisation
 Myositis34 Muscle inflammation including idiopathic, autoimmune, and infectious aetiologies with possible superimposed abscess in the latter (see pyomyositis)Increased muscle echogenicity and possible distortion of the muscle architecture with increased muscle size when acute and variable increased flow on Doppler imaging; other conditions such as rhabdomyolysis may have a similar appearance.
Pyomyositis35 36 Muscle abscessCircumscribed heterogeneous fluid collection ranging from anechoic to hyperechoic with increased through transmission and commonly peripheral increased flow on Doppler imagingClinical features may help in differentiating from other causes of fluid collection within a muscle.
Fatty Infiltration34 Fat infiltration of muscle from disuse, dysfunction, injury or denervation, among other causes, with the term atrophy used when muscle is also decreased in size.Diffuse increased muscle echogenicity with possible decrease in muscle size when atrophic (figure 3D)
(C) Ligament
Sprain37 38 A clinical/biomechanical term, which is not well defined and used inconsistently for different ligament injuriesDepends on severity of injuryGenerally, refers to an elongation or stretch type of injury
Tear37 38 Injury to ligament fibres which may include partial or complete ligament disruptionPartial or complete ligament disruption with variable degrees of laxity on stress imaging based on severity of injury; echogenicity and ligament thickness are variable; possible increased flow on Doppler imaging (figure 4A,B)Numerous clinical and imaging-based classification and grading systems for specific ligament injuries exist.
AvulsionLigament tear at its bony attachment or a fracture at a ligament attachment.Variable, depending on specific pathology (see other more precise terms)Due to a traction mechanism (as opposed to direct trauma)
(D) Joint recess, bursa and tendon sheath
TermDefinitionUltrasound appearance
Effusion39–42 Distention of a synovial space with fluid from several possible aetiologies, including but not limited to, mechanical, reactive, and inflammatory mechanisms, among othersFluid distention of a synovial space of variable echogenicity depending on composition (figure 5A)
Synovial hypertrophy39–41 Thickened synovium characteristic of several aetiologies, including, but not limited to, mechanical, reactive, and inflammatory (infection or inflammatory arthritis) mechanisms.Variable echogenicity (most commonly hypoechoic) non-compressible or minimally compressible tissue with variable flow on Doppler imaging; increased blood flow could indicate active inflammation (termed synovitis as described below).
Synovial proliferation43 Thickened synovium due to several non-inflammatory etiologies, such as pigmented villonodular synovitis, lipoma arborescens and synovial chondromatosis (which is often mineralised).Variable echogenicity non-compressible or minimally compressible synovial thickening or mass-like appearance with variable flow on Doppler imaging (figure 5B)
Synovitis39–41 44 Inflammation of the synovium within a joint recess, tendon sheath or anatomic bursa; use a more specific term (eg, tenosynovitis) whenever possible.Variable echogenicity (most commonly hypoechoic) synovial tissue that is not displaceable and minimally compressible with possible increased flow on Doppler imaging (figure 5C)
Bursitis45 Inflammation of bursaVariable, depending on the underlying pathology, which can include effusion, synovial hypertrophy, synovial proliferation and synovitis with possible increased flow on Doppler imaging
(E) Nerve
NeuropathyA term that encompasses several nerve conditionsVariable, depending on specific pathological processThe use of a more precise term is recommended when describing imaging findings if possible.
Compression neuropathy46–48 Disorder characterised by nerve dysfunction as a result of nerve entrapment or extrinsic impingementHypoechoic appearance of nerve from epineural oedema with possible fascicular enlargement typically proximal and sometimes distal to the compression site (figure 6A)Nerve compression first results in oedema followed by demyelination and then ischaemic axonal damage when the compression is severe and chronic
Transection49 Partial or complete discontinuity of a nerve due to disruption of some or all the nerve fasciclesDiscontinuity of some or all nerve fascicles with possible retraction of the discontinuous nerve and focal or mass-like thickening at the retracted end (see neuroma) (figure 6B)
Neuroma49 50 The focal enlargement of an injured nerve or fascicle, which may be associated with nerve or fascicular retraction if due to transectionHypoechoic focal nerve or fascicle enlargement at the site of injury with possible retraction (figure 6C)
Neuritis51 Nerve inflammation as seen with inflammatory, infectious or autoimmune conditionsAbnormally hypoechoic nerve with possible increased flow on Doppler imaging
(F) Fascia
Fasciopathy52 53 A term that encompasses several fascial conditionsVariable, depending on the specific pathological processThe use of a more precise term is recommended when describing imaging findings if possible.
Fasciosis52 53 A chronic condition characterised histologically as degeneration, collagen necrosis, angiofibrotic hyperplasia, chondroid metaplasia and fibrosis; although primarily a degenerative process from mechanical overload with absence of an acute inflammatory infiltrate, inflammatory mediators may be present.Hypoechoic thickening of the fascia with possible calcification and possible increased flow on Doppler imaging (figure 7)
Fasciitis54 Inflammation of fasciaHypoechoic thickening of the fascia with possible increased flow on Doppler imaging
TearInjury to fascial fibres which may include partial or complete disruptionPartial or complete disruption with variable echogenicity and thickness and possible haemorrhage of variable echogenicity; there may be loss of tension with complete disruption; possible increased flow on Doppler imaging
(G) Bone
OsteophyteA bony excrescence at the margin of a synovial articulation as a manifestation of osteoarthritis (or osteoarthrosis)Hyperechoic bony excrescence typically at the margin of a synovial articulation
EnthesophyteA bony excrescence at a tendon, ligament or fascia attachment, typically as a manifestation of overuse, tension, prior injury or adjacent tendinosis (when well defined) or inflammation (when ill-defined with possible erosions termed enthesitis or inflammatory enthesopathy)Hyperechoic bony excrescence at a tendon, ligament or fascia attachment;
may be well defined or ill-defined with possible associated erosions and possible increased flow on Doppler imaging
Erosion40 Cortical discontinuity in a subsynovial or enthesis location, a manifestation of inflammation (infection or inflammatory arthritis) with possible associated synovial hypertrophyDiscontinuity of the hyperechoic cortical bone surface in a subsynovial or enthesis location confirmed in two planes, may have associated synovial hypertrophy (see previously mentioned definition) and possible increased flow on Doppler imagingThere are many causes for cortical irregularity, and the finding of adjacent synovitis adds specificity to the diagnosis of cortical erosion.
(H) Miscellaneous
TermDefinition
HyperaemiaIncreased blood flow due to neovascularity (as seen in tendinosis and tumours) and/or vasodilation due to inflammation (as in inflammatory synovitis or infection).
SubluxationWhen a structure is partially displaced from its normal anatomical location, possibly only occurring with dynamic manoeuvres (ie, dynamic subluxation); the word ‘sublux’ and ‘subluxed’ do not exist in the English dictionary and should be avoided in favour of subluxate and subluxation.
DislocationWhen a structure is completely displaced from its normal anatomical location, including those occurring with dynamic manoeuvres (ie, dynamic dislocation)