DOI:10.2214/AJR.09.2808
AJR 2009; 193:607-618
© American Roentgen Ray Society
Sonography of Common Tendon Injuries
Philip Robinson1
1 X-ray Department, Musculoskeletal Centre, Chapel Allerton Hospital, Leeds
Teaching Hospitals, Leeds LS7 4SA, UK.
Received March 26, 2009;
accepted after revision May 21, 2009.
Address correspondence to P. Robinson
(p.robinson{at}leedsth.nhs.uk).
Abstract
OBJECTIVE. The purpose of this article is to describe the normal and
abnormal appearances of the tendons most easily and commonly assessed with
sonography.
CONCLUSION. Sonography is important in musculoskeletal imaging, and
its accuracy is at least equivalent to that of MRI for imaging tendon
abnormalities. Although operator dependence is an often quoted disadvantage of
sonography, most experienced musculoskeletal radiologists with a sound
foundation in anatomy can rapidly master the technique and perform effective
evaluations of normal and abnormal tendons.
Keywords: athletic injury • Doppler • tendinopathy • tendon • ultrasound
Introduction
Tendons consist of linear fibrils of collagen with a supporting matrix. The
fibrils are oriented in a direction specific to the forces applied from the
interaction between a tendon and its muscle and skeletal attachment
[1,
2]
(Fig. 1). During movement,
tendons shorten and lengthen as springs do, transmitting and absorbing forces
[2]. Normal tendon is elastic
and re-forms on withdrawal of applied forces, within the physiologic range.
Acute catastrophic tears of normal tendons are extremely rare, overuse
injuries being more common [3].
Areas of friction (e.g., the malleoli), impingement (e.g., the rotator cuff),
and force concentration during contraction (e.g., the Achilles tendon) are
important in the development of chronic mechanical damage and tendinopathy
[4]. Vascularity is also
considered important in tendon disease. Some authors
[1,
2] believe that areas of
relatively poor vascular supply (e.g., the mid Achilles tendon) also are
predisposed to tendinopathy owing to impaired tendon healing.
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Fig. 1 —23-year-old woman with healthy knee. Longitudinal sonogram
shows normal fibrillar pattern of patellar tendon (arrowheads) and
normal deep infrapatellar bursal fluid (arrow). T = tibia, P =
patella.
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Overview of Technique
The major tendons are predominantly superficial and can be assessed with a
high-frequency linear transducer (9–17 MHz) with a thick layer of
coupling gel. The examiner should hold the transducer near its footprint and
spread the other fingers out to stabilize the transducer on the skin surface
[5–7].
This stability is essential when the instrument is placed on prominences such
as the Achilles tendon and medial malleolus and allows the small controlled
movements needed to differentiate pathologic findings from anisotropy.
Anisotropy is an artifact produced by the linear configuration of tendons
whereby hypoechoic change is seen if the transducer is slightly angulated
[5,
7] (Fig.
2A,
2B,
2C,
2D). This artifact can mimic
hypoechoic tendinopathy, but careful minor changes to transducer angulation
make anisotropy disappear whereas true pathologic findings do not. Anisotropy
can be beneficial for confirming tendon position because the artifact can be
produced in the linear tendon while the surrounding nonlinear echogenic fat is
not affected, increasing contrast between the two structures
(Fig. 2D).
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Fig. 2A —46-year-old man with normal Achilles tendon. Longitudinal
sonogram shows normal fibrillar pattern (arrows), calcaneal insertion
(C), and minor anisotropy involving Sharpey's fibers
(arrowheads).
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Fig. 2B —46-year-old man with normal Achilles tendon. Longitudinal
sonogram shows transducer angulation producing anisotropy
(arrowheads) more marked than in A. Arrows indicate normal
fibrillar pattern. C = calcaneal insertion.
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Active or passive movement can be used for dynamic evaluation of all
tendons for tear severity and abnormal movement due to subluxation and
adhesive tenosynovitis. Interrogation with power Doppler technique is
performed if tendon abnormality is seen, although the exact significance of
neovascularity is not clear (see later)
[8–11].
Power Doppler settings are set to optimize low flow, and gain is reduced and
increased until signal from adjacent bone is eliminated
[11] (Fig.
3A,
3B). Excessive transducer
pressure and tendon tension can compress and artificially eliminate
neovascularity. During Doppler assessment, the tendon should be in a relaxed
position, contrary to the tensed position in which tendons are typically
evaluated for tears and tendinopathy.
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Fig. 3A —29-year-old male soccer player with proximal patellar
tendinopathy. Longitudinal sonogram shows marked hypoechoic tendinopathy
(asterisk), neovascularity, and irregularity of inferior patellar
cortex (arrow).
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Overview of Ultrasound Appearances of Tendon Abnormalities
Tenosynovitis and Paratenon Edema
In its immediate environment, a tendon can be enclosed or surrounded by a
synovial sheath (e.g., wrist and ankle) or a paratenon of loose vascular
areolar connective tissue (e.g., patellar and Achilles tendons)
[12,
13]. Many tendons also have
adjacent bursae (e.g., rotator cuff and iliopsoas). Overuse injury can produce
hypoechoic edema, fluid, or synovitis in these surrounding structures, often
before intrinsic tendon abnormality occurs (e.g., Achilles tendon and rotator
cuff) (Fig. 4). Care should be
taken with some tendon sheaths because they communicate directly with adjacent
joints (e.g., proximal biceps, flexor hallucis longus). Therefore, a
sonographic diagnosis of tenosynovitis should only be made if inflammatory
changes are localized to the sheath and joint effusion is excluded.
Tendinopathy
Tendinopathy can be caused by overuse, external impingement, and
age-related changes (the term preferred to degeneration)
[4,
14]. At sonography, early
tendinopathy initially appears as tendon thickening, and observation of
changes in the normal contour and echotexture is more practical than relying
on absolute measurements (Fig.
5). As tendinopathy progresses, the fibrillar pattern is lost and
replaced by hypoechoic changes with further swelling
[5,
14]. These features can be
focal or can progress to involve the full tendon thickness (Figs.
5 and
6). If severe tendinopathy is
present, dynamic evaluation (i.e., during movement) should be performed to
rule out partial tear (Fig.
7).
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Fig. 7 —39-year-old man with severe Achilles tendinopathy.
Longitudinal sonogram shows convex tendon thickening (arrows), loss
of fibrillar pattern, and focal linear hypoechoic change
(arrowheads), which did not distract on movement.
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Power Doppler interrogation should be performed to look for
neovascularization within an abnormal tendon (Fig.
3A,
3B). The importance of this
finding is not fully understood, but normal tendons do not exhibit
neovascularity. Results of some studies have suggested that neovascularity
initially correlates with pain severity, but a consistent relation to poorer
outcome has not been found
[11]. All of the sonographic
findings of tendinopathy can potentially be seen at an asymptomatic stage, but
prominent tendon swelling, loss of fibrillar structure, and neovascularity
usually are associated with severe symptoms
[11,
14,
15].
Partial and Complete Tears
Tears of normal tendons are extremely rare and are usually part of severe
acute injury. Tears more commonly are associated with background tendinopathy,
which weakens the tendon sufficiently to allow a chronic tear to progress or a
relatively minor injury to precipitate complete disruption. Tendon margins can
be separated by fluid, hematoma, and herniated adjacent tissues
(Fig. 8). If the torn margins
remain apposed, the presence of edge artifact suggests a tear is present, and
separation is confirmed with dynamic movement (Fig.
9A,
9B).
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Fig. 8 —46-year-old man with full-thickness tear of Achilles tendon.
Longitudinal sonogram shows separated tendon ends (arrows), hematoma
(arrowhead), and pre-Achilles fat herniating into gap
(asterisk).
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Fig. 9B —52-year-old man with full-thickness tear of Achilles tendon.
Longitudinal sonogram obtained during dorsiflexion shows complete separation
and increased edge artifact (arrowheads). Asterisk indicates
hematoma.
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Differential Diagnosis and Associated Injuries
Particularly around the ankle, sonography can be used to diagnose numerous
soft-tissue injuries that can be confused with tendon injury on the basis of
clinical findings. Although outside the scope of this review, adjacent
capsular, joint, and ligamentous injury always should be assessed during
sonographic examinations. Dynamic evaluation is particularly useful in the
detection of adhesions, impingement, tendon subluxation, and retinacular
injuries (Fig. 10A,
10B).
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Fig. 10A —26-year-old woman with partial peroneal retinacular injury.
Transverse sonogram obtained with gel standoff (asterisk) shows
lateral malleolus (LM), peroneal tendon (P), and edematous linear retinaculum
(arrowheads).
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Fig. 10B —26-year-old woman with partial peroneal retinacular injury.
Transverse sonogram obtained during forced eversion shows tenting of
retinaculum (arrowheads) but no dislocation. Asterisk indicates gel
standoff. LM = lateral malleolus.
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Tendon-Specific Assessment
Shoulder
Rotator cuff tear, tendinopathy, and impingement are common indications for
sonographic evaluation. The examination is performed from the front of the
patient with the patient sitting. This position makes it easier for the
examiner to judge the patient's discomfort during movement and to perform
guided injections. Positioning for sonography is not simple, but it is vital
for obtaining adequate views of all tendons
[6,
7,
16].
The biceps tendon is evaluated in the bicipital groove with the arm in a
neutral position and the hand resting palm up on the patient's thigh. The
subscapularis tendon is evaluated as the patient moves the arm into full
external rotation (Figs. 11A,
11B,
12,
13). The supraspinatus and
infraspinatus tendons, rotator interval, and subacromial bursa are best
evaluated in internal rotation with the hand placed behind the back or palm on
the back pocket, or Crass, view
[6,
7,
16,
17]
(Fig. 14).
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Fig. 11A —26-year-old man with normal shoulder tendons. Transverse
sonogram obtained with arm in neutral position shows normal biceps tendon
(arrow), transverse ligament (arrowheads), and subscapularis
tendon (S).
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Fig. 11B —26-year-old man with normal shoulder tendons. Transverse
sonogram obtained with arm in external rotation shows subscapularis tendon
(arrows) and normal insertional anisotropy (arrowheads).
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Fig. 12 —39-year-old man with clinical findings of proximal biceps
tenosynovitis. Transverse sonogram shows hypoechoic biceps tendinopathy
(arrow) and marked tenosynovitis (arrowheads). No fluid was
detected in joint or other recesses.
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Fig. 13 —27-year-old man with previous shoulder dislocation and
subscapularis tear. Transverse sonogram shows distal tear (asterisk)
of subscapularis tendon (small arrows) that allows medial
biceps subluxation (large arrow) from groove
(arrowheads).
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Fig. 14 —24-year-old woman with normal shoulder tendons. Transverse
sonogram obtained with shoulder in internal rotation shows humeral head (H),
deltoid muscle (D), hypoechoic articular cartilage (arrowheads), and
multipennate supraspinatus tendon (arrows) extending up to rotator
interval. B = biceps, I = infraspinatus.
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The biceps tendon is homogeneous and linear, appearing echogenic within the
bicipital groove. Its intraarticular course cannot be followed fully, but the
rotator interval can be assessed, and within the bicipital groove,
tenosynovitis, tears, and subluxation all can be visualized (Figs.
12 and
13). Proximal tendon rupture
rarely requires primary imaging because the patient has the classic Popeye
sign caused by the distal retracted tendon. Proximal biceps rupture or the
presence of sheath fluid can be associated with supraspinatus tear, however,
so detection should prompt careful evaluation of the rest of the rotator cuff.
Subluxation or dislocation of the biceps tendon occurs after transverse
humeral ligament and bicipital pulley tear with possible subscapularis tear
(Fig. 13). More rarely, biceps
rupture occurs due to impingement from bicipital groove spurs or
osteophytes.
The other rotator cuff tendons normally appear slightly more heterogeneous
than the biceps tendon because they are multipennate, essentially consisting
of multiple curved tendon units. These minitendons interdigitate as they form
the cuff, producing a degree of inherent anisotropy
(Fig. 14). In the long axis,
the tendons are curved like eagles' beaks. In the short axis the supraspinatus
and infraspinatus tendons sit like a toupee on the humeral head
(Fig. 15).
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Fig. 15 —29-year-old man with normal shoulder tendons. Longitudinal
sonogram obtained during internal rotation shows echogenic fibrillar
supraspinatus tendon (arrows) with insertional footprint and
characteristic eagle's beak appearance. Subacromial bursa is thin and
difficult to visualize (arrowheads).
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Severe subscapularis tendinopathy can occur in the context of previous
dislocation (Fig. 13) or as
part of a massive rotator cuff tear. The subscapular bursa or recess
communicates with the joint, and the presence of fluid is associated with a
higher incidence of rotator cuff tear, so careful examination of the
supraspinatus and infraspinatus tendons is required if fluid is seen
[18]. Minor underlying humeral
irregularity is common with subscapularis tendinopathy, but more marked cystic
changes can be associated with tears
[19].
Supraspinatus tendinopathy is common and in its earliest stages occurs at
the anterior and distal tendon edges
[6,
7,
16]. Initially this area is
best evaluated in the short axis with the shoulder in internal rotation (Figs.
14,
15,
16). The coracoid process is a
good landmark, and the transducer is moved laterally from there for
visualization of the anterior cuff edge and biceps at the rotator interval. At
this point, the anterior edge of the supraspinatus tendon should be
immediately adjacent to the echogenic biceps tendon
(Fig. 14). There can be a
slight gap if the patient has undergone tendon repair or in the presence of a
large amount of joint fluid. Tendinopathy is seen as hypoechoic swelling, and
as the pathologic changes become more severe, discrimination of small partial
tears can be difficult (Figs.
16 and
17)
[6,
7,
16]. Partial tears are seen as
a focal area of hypoechoic change with free fluid occasionally extending into
the gap (Figs. 18 and
19). Similarly, partial- and
full-thickness tears most commonly occur in this anterior position, but tears
can less frequently be midsubstance or intrasubstance
(Fig. 18). A tear is
visualized as a tendon defect with the margins separated by fluid or herniated
deltoid and subacromial bursa (Figs.
20,
21,
22).
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Fig. 16 —44-year-old woman with supraspinatus tendinopathy. Transverse
sonogram shows swelling of anterior edge of supraspinatus tendon and
tendinopathy (thick arrows), articular cartilage
(arrowhead), biceps (thin arrow), and adjacent normal tendon
(asterisk).
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Fig. 17 —49-year-old man with supraspinatus tendinopathy. Transverse
sonogram shows swelling of anterior aspect of supraspinatus tendon with focal
hypoechoic change (arrow) and marked echogenic subacromial bursal
thickening (arrowheads). B = biceps, H = humerus.
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Fig. 18 —38-year-old man with intrasubstance tear of right
supraspinatus tendon. Transverse sonogram shows thickened supraspinatus
tendinopathy, normal cartilage (arrowhead), and linear intrasubstance
tear with fluid (arrows).
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Fig. 20 —38-year-old woman with full-thickness tear of left
supraspinatus tendon. Longitudinal sonogram shows full-thickness retracted
tear (arrows) from greater tuberosity (GT) with underlying cortical
irregularity (arrowhead).
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Fig. 21 —64-year-old man with full-thickness tear of right
supraspinatus tendon. Transverse sonogram shows large chronic supraspinatus
and infraspinatus tears and missing tendons replaced by displaced
(arrows) herniated deltoid (D). Arrowhead indicates humeral (H)
cortical irregularity. B = biceps.
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Fig. 22 —56-year-old man with full-thickness tear of left
supraspinatus tendon. Longitudinal sonogram shows small hypoechoic
full-thickness supraspinatus tear (arrowheads), underlying cortical
irregularity (arrows), and relatively normal tendon margins
(asterisks).
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Cortical irregularity of the greater tuberosity commonly is associated with
an adjacent supraspinatus tendon tear (Figs.
20,
21,
22)
[20]. Intratendon
calcification is not uncommonly part of the spectrum of tendinopathy and can
range from multiple submillimeter areas through ill-defined liquid change to
large dense mature deposits (Figs.
23 and
24). The role of calcification
in impingement is not clear, and calcification commonly is present in the
absence of symptoms. Intratendon calcification is more frequent in women than
in men, and it is thought [7]
that pain results from chemical release of mediators and increasing
impingement. Acoustic shadowing from dense calcification can make it difficult
to fully evaluate for minor partial tears, but full-thickness tears are easily
excluded (Fig. 24).
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Fig. 23 —48-year-old woman with left supraspinatus calcification.
Longitudinal sonogram shows humerus (H), supraspinatus swelling due to
ill-defined echogenic calcification (arrows), and subacromial bursal
thickening (arrowheads). Little acoustic shadowing is present. Milky
fluid was aspirated.
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Fig. 24 —57-year-old woman with left supraspinatus calcification.
Longitudinal sonogram shows dense mature echogenic calcification
(arrowheads) and acoustic shadowing (arrows) within
supraspinatus tendon.
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Subacromial bursal thickening should be evaluated and is seen as widening
of the normally thin hypoechoic stripe overlying the cuff tendons (Figs.
15 and
17). Free bursal fluid is not
common, but bunching of the thickened bursa can sometimes be visualized during
arm abduction from the neutral or internally rotated position
[6,
21] (Fig.
25A,
25B). The power and
significance of the results of this test have not been validated
clinically.
Elbow
The severity of sonographic findings does not always correlate well with
clinical severity [22,
23]. Thus the degree of
tendinopathy seen may not alter primary management, but the presence of actual
tearing may influence surgical management owing to potential ligamentous
involvement [23]
(Fig. 26).
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Fig. 26 —53-year-old woman with tear of origin of right common
extensor tendon. Longitudinal sonogram shows lateral epicondyle (Ep), radial
head (R), and partial tear of deep part of common extensor tendon with intact
superficial aspect (arrow) but edema and synovitis extending down
from tear (arrowheads) to disrupted lateral collateral ligament and
joint capsule.
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Distal biceps abnormality can be accurately assessed at sonography, and the
tendon is initially best evaluated in the short axis. Scanning begins at the
biceps myotendinous junction and moves distally. Constant readjustment of
transducer angulation is necessary to confirm position and reduce anisotropy
because the tendon curves markedly as it passes to insert into the radial
tuberosity. For this reason, longitudinal imaging of a normal tendon can be
difficult and is made easier when the axial position is confirmed for
guidance. An abnormal tendon may be easier to locate because it is typically
hypoechoic, enlarged, or surrounded by bursitis and hematoma (Fig.
27A,
27B).
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Fig. 27A —54-year-old woman with tendinopathy of right distal biceps
tendon. Transverse sonogram shows thickened hypoechoic tendinopathy
(arrows) of distal aspect of biceps tendon at level of capitellum
(C).
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Fig. 27B —54-year-old woman with tendinopathy of right distal biceps
tendon. Longitudinal sonogram shows partial linear tear (arrows) on
deep surface at radial tuberosity (RT) distal to degenerated radial head
(RH).
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Wrist
Common reasons for referral for wrist sonography involve focal overuse
injuries to the wrist and fingers resulting from retinacular friction
[7]. As with the ankle,
accurate evaluation of the wrist and hand tendons is initially best performed
in the transverse plane (short axis) because of the number and proximity of
multiple tendons [7]. Any area
affected by symptoms is scanned transversely, and scanning proceeds along the
tendons to the wrist to confirm the anatomic features. The affected tendon or
compartment is identified on the dorsal aspect of the wrist with Lister's
tubercle as a reference point (Fig.
28).
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Fig. 28 —Diagram shows dorsal wrist anatomy. With Lister's tubercle
(black arrow) as landmark, extensor compartments (I–VI) and
tendons can be identified. I = abductor pollicis longus and extensor pollicis
brevis, II = extensor carpi radialis longus and brevis, III = extensor
pollicis longus, IV = extensor indicis and digitorum, V = extensor digiti
minimi, VI = extensor carpi ulnaris, U = ulna, R = radius.
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De Quervain tenosynovitis involves the abductor pollicis longus and
extensor pollicis brevis tendons of the first extensor compartment. Chronic
retinacular friction leads to painful hypoechoic tendinopathy, tendon
swelling, and retinacular and synovial thickening
[7]
(Fig. 29). In the more
proximal aspect, intersection syndrome involving the extensor carpi radialis
tendons where they are crossed by the first extensor compartment muscles can
be similarly defined [7].
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Fig. 29 —44-year-old man with de Quervain disease of right wrist.
Transverse sonogram shows thickened hypoechoic abductor pollicis longus
(arrowhead) and extensor pollicis brevis (arrow) tendons
with increased power Doppler flow (asterisks) indicating retinacular
thickening and tenosynovitis. R = radius, A = radial artery.
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In the fingers, imaging of the flexor tendons may be needed to confirm
sheath and pulley thickening (trigger finger)
[24]
(Fig. 30). Acute pulley
injuries, increasingly common among recreational climbers, also can be defined
(Fig. 31). Tendon lacerations
or tears occur in direct trauma and inflammatory arthritis. The affected
finger directs the area to be examined, where the tendon can be assessed for
partial and retracted full-thickness tears. When focal tendinopathy or
tenosynovitis is detected, sonography is useful to define adjacent entities,
such as osteophytes, orthopedic hardware, and soft-tissue masses, that
contribute to impingement
[25].
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Fig. 30 —49-year-old woman with locking ring finger. Longitudinal
sonogram of proximal interphalangeal joint of fourth finger shows normal
flexor tendon (arrow), anisotropy (asterisk), and multiple
hypoechoic areas of sheath thickening (arrowheads) consistent with
stenosing tenosynovitis (trigger finger).
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Fig. 31 —34-year-old male climber with acute rupture of finger pulley.
Longitudinal sonogram of proximal phalanx (PP) of second finger shows slightly
thickened intact flexor tendon (asterisk) with adjacent hemorrhage
and edema (arrows) displacing tendon away form phalanx. Findings are
consistent with A2 pulley rupture.
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Hip and Pelvis
Abnormalities of the pelvic tendons include hamstring peritendinitis,
gluteal tendinopathy, iliotibial band friction, adductor longus tendinopathy,
and snapping tendons around the hip
[26,
27]. Gluteal tendinopathy is a
common cause of lateral hip pain commonly attributed to bursitis, but true
bursal fluid is rarely found
[7,
28]. Tendinopathy is common in
patients older than 40 years, and therefore its presence is not a specific
finding [28]
(Fig. 32). Ultrasound can be
used, however, to guide injection.
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Fig. 32 —68-year-old woman with left gluteal tendinopathy.
Longitudinal extended field of view sonogram shows greater trochanter (GT)
with loss of definition of overlying gluteal tendons due to hypoechoic
tendinopathy and swelling (arrows).
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Iliopsoas snapping can be an overuse injury in athletes or be caused by
impingement from an adjacent acetabular abnormality (osteophyte or prosthesis)
(Fig. 33). The tendon is best
visualized in the transverse (short axis) view anterior to the hip and
iliopectineal eminence. The tendon can be assessed for adjacent acetabular
abnormality, bursitis, and vibrating rotation on hip flexion, the last being
associated with snapping [27]
(Fig. 34).
Patella
Patellar tendinopathy is a frequent source of symptoms due to overuse and
aging [4,
7,
14]. In athletes and the
general population, the patellar tendon is most frequently abnormal in the
central proximal aspect adjacent to the inferior pole of the patella
[7,
29] (Fig.
3A,
3B). Controversy exists about
whether the patellar pole contributes compressive mechanical forces or whether
the changes are secondary to tensile overuse
[4,
29].
The patellar tendon is best evaluated tensed and straightened with the
patient supine, the hip and knee flexed, and the foot flat
(Fig. 1)
[6,
7,
16]. The tendon can be easily
evaluated in both axes for tendinopathy, swelling, partial tear,
neovascularity, and adjacent patella cortical irregularity (Figs.
3A,
3B and
35). Unlike in the Achilles
tendon, paratenon edema is rarely seen, but small amounts of deep
infrapatellar bursal fluid are normally seen between the tendon, tibia, and
Hoffa's fat pad (Fig. 1).
Ankle
Achilles tendon—The large Achilles tendon obtains its blood
supply from its paratenon with additional input from the triceps surae muscles
at the myotendinous junction and the calcaneum at the enthesis
[3,
30]. Vascular and
biomechanical factors have been proposed to explain why the area 4–6 cm
proximal to the calcaneus is especially predisposed to tendinopathy and
subsequent tearing [4,
30]. The tendon does not move
in a linear manner with all three components rotating medially so that the
soleus component moves from the deep to the medial aspect. It is thought that
repetitive twisting and untwisting lead to stress concentration, which is
exacerbated in relatively avascular areas of the tendon, further limiting its
ability to repair damage
[13].
The Achilles tendon (biceps and patellar tendons) normally is highly
fibrillar and echogenic, and anisotropy occurs where the fibers curve at the
calcaneal insertion (Fig. 2A,
2B,
2C,
2D). In axial section, the
tendon usually has a flat deep aspect or is slightly horseshoe shaped
[11] (Fig.
2A,
2B,
2C,
2D). Evaluation is easiest with
the patient prone with both feet hanging over the table edge, which also
allows passive or active movement of the foot and Achilles tendon
[6,
7,
16].
Normally no fluid is present around the Achilles tendon. Paratenon change
is more frequently imaged in athletes because it can develop subacutely during
intensive preseason training or rehabilitation
[13]. Paratenon change and
tendinopathy are more commonly seen on the medial aspect of the tendon
[3,
13]
(Fig. 4). Initially the
underlying tendon is typically normal with adjacent hypoechoic edematous fat
and fluid extending a few centimeters in the craniocaudal direction. The main
differential diagnosis of this appearance is plantaris rupture, but for that
diagnosis, the history is acute and the torn tendon ends are seen at either
margin of the edema.
As tendinopathy develops, the tendon becomes more swollen and can be
described as spindle shaped (Figs.
5 and
6). With severe changes, the
entire tendon from the myotendinous junction to the calcaneus can be involved.
At this point, detection of an intrasubstance or partial tear can be difficult
but is aided by active or passive dorsiflexion and plantarflexion
(Fig. 7).
Full-thickness tears usually occur in diseased tendons, but there is an
acute incident in the history. Tears can be difficult to confirm clinically if
marked swelling or an intact plantaris tendon is present, which allows
appropriate movement during the examination (Fig.
36A,
36B). At sonography, fluid can
be seen separating the torn margins, which can also exhibit edge artifact
(Fig. 8). Subacute
presentations can be more difficult to analyze because intervening hematoma
can mimic tendinopathy, but increased separation of the tendon margins is
usually seen during dorsiflexion (Fig.
9A,
9B). The role of sonography is
not only to confirm the extent of the tear but also to document the degree of
separation in full dorsiflexion and plantarflexion. These features and whether
the ends fully appose in plantarflexion may dictate whether nonsurgical
treatment can continue.
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Fig. 36A —52-year-old man with suspected full-thickness tear of
Achilles tendon but equivocal findings at clinical examination. Longitudinal
(A) and transverse (B) sonograms immediately superior to
calcaneus show extensive hemorrhagic tissue (arrows), no evidence of
Achilles tendon, and intact plantaris tendon (arrowheads).
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Fig. 36B —52-year-old man with suspected full-thickness tear of
Achilles tendon but equivocal findings at clinical examination. Longitudinal
(A) and transverse (B) sonograms immediately superior to
calcaneus show extensive hemorrhagic tissue (arrows), no evidence of
Achilles tendon, and intact plantaris tendon (arrowheads).
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Insertional tendinopathy is uncommon on its own but can be seen with
inflammatory arthritis or be caused by ill-fitting footwear. Retrocalcaneal
bursitis can be associated with chronic tendinopathy but also can clinically
mimic tendinopathy developing from overuse or underlying calcaneal prominence
(Haglund's deformity) (Fig.
37).
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Fig. 37 —42-year-old woman with left heel pain. Longitudinal sonogram
shows upper calcaneus (C), Haglund bony deformity (Ha), retrocalcaneal
bursitis (asterisk), and relatively minor Achilles tendinopathy
(arrows).
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Other ankle tendons—Peroneal, tibialis, and flexor hallucis
tendinopathy can be isolated or be associated with other ankle and foot
abnormalities [31]. These
lesions can include previous injuries or surgery, coalition, and osseous spurs
and retinacular injuries, which can cause chronic stresses acting through the
tendons [4,
32,
33].
The ankle tendons have a curved course and are close together at the
malleoli. It is therefore easier and more reliable to evaluate them in the
short axis because this view allows complete assessment of the tendon cross
section and prevents mistaken slippage to an adjacent tendon
(Fig. 38). The malleoli are
the starting landmarks for the peroneal and posteromedial tendons
[6,
7,
16]. The tendon to be
evaluated is selected and scanned in the superior direction to the
myotendinous junction and then in the distal direction in a search for
tendinopathy, tears, and tenosynovitis
(Fig. 39). Constant adjustment
of transducer angulation is required to follow the curved course of the tendon
and eliminate anisotropy. Tears of these tendons are typically degenerative
longitudinal splits, particularly around the malleoli
[34].
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Fig. 38 —42-year-old man with normal ankle. Transverse sonogram shows
medial malleolus (MM), tibialis posterior tendon (TP), flexor digitorum longus
(FDL) tendon and muscle, blood vessels (large arrowheads),
tibial nerve (arrow), flexor hallucis longus tendon (FHL), and
overlying extensor retinaculum (small arrowheads).
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Fig. 39 —31-year-old woman with pain in posterior aspect of right
ankle. Longitudinal sonogram shows posterior aspect of talus (Ta), normal
flexor hallucis longus tendon (arrowhead), and multiple hypoechoic
areas of tenosynovitis (arrows), which inhibit active movement.
Tibiotalar joint effusion was not present.
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The tibialis posterior is normally much larger than the other ankle
tendons. Hypoechoic tendinopathy can progress to longitudinal splits at the
malleolus and immediately proximal to its navicular insertion (Figs.
40 and
41)
[31]. The very distal
insertion is often difficult to fully visualize because of anisotropy where
the tendon fans out broadly with multiple slips to different tarsal bones.
Normal variation of the medial navicular insertion may further complicate this
area with ossicles visualized within the tendon
[7].
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Fig. 40 —57-year-old man with left tibialis posterior tendinopathy.
Transverse sonogram distal to medial malleolus shows markedly thickened
hypoechoic tibialis posterior tendon (arrows), tenosynovitis
(asterisk), and neovascularity.
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Fig. 41 —42-year-old woman with right tibialis posterior tear.
Longitudinal sonogram shows swollen tibialis posterior tendon
(arrows), intrasubstance splitting (arrowheads), and
tenosynovitis (asterisk).
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The flexor digitorum longus and extensor tendons rarely are affected by
pathologic conditions outside of specialized sports injuries and systemic
arthritis. Flexor hallucis longus tenosynovitis can develop in kicking
athletes and ballet dancers. The tenosynovitis is best seen at the level of
the posterior aspect of the ankle. Any stenotic tenosynovitis is best
appreciated dynamically with restricted tendon movement in the longitudinal
plane (Fig. 39).
The peroneal tendons most frequently exhibit abnormality at the lateral
malleolus and more distally at the peroneal tubercle on the lateral aspect of
the calcaneus, where the common tendon sheath splits to allow the tendons to
separate [3,
30]. The peroneus brevis
tendon can then be followed to the base of the fifth metatarsal. Particularly
at the lateral malleolus, it is important to evaluate for adjacent bony (e.g.,
spurs, orthopedic hardware) (Fig.
42) and retinacular abnormality contributing to tendon disease
[6,
7,
16]. Chronic peroneus brevis
tendinopathy produces the short-axis appearance of curving (horseshoe shape)
and enlargement of the peroneus brevis tendon before longitudinal splitting
[7,
35]
(Fig. 43).
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Fig. 42 —47-year-old man with right ankle pain and previous fibular
fracture fixation. Transverse sonogram at lateral malleolus (LM) shows
peroneus brevis (asterisk) and high-grade intrasubstance tear of
peroneus longus tendon (arrowheads) due to attrition from adjacent
fixation screw (arrow).
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Fig. 43 —49-year-old man with right peroneus brevis tear. Transverse
sonogram shows enlarged hypoechoic and C-shaped peroneus brevis tendon
(arrows) consistent with tendinopathy and longitudinal splitting
enveloping relatively normal peroneus longus tendon (arrowheads).
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Peroneal tendon subluxation over the fibula occurs with peroneal
retinacular injury [34]
(Fig. 44). To confirm this
finding at sonography, the examiner applies a copious amount of gel to the
area over the malleolus as a standoff so that transducer pressure does not
prevent movement. The patient is asked to evert the foot against the
examiner's hand; if the retinaculum is intact or only lax, the tendons will
rise but be contained (Fig.
9A,
9B).
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Fig. 44 —29-year-old woman with left peroneal retinaculum tear.
Transverse sonogram during forced (active against resistance) eversion shows
peroneus brevis subluxation (arrow) and edematous peroneal
retinaculum (asterisk) peeled away (arrowheads) from lateral
malleolus (LM). PL = peroneus brevis tendon.
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Conclusion
Ultrasound is an efficient and accurate imaging method for evaluation of
common tendon abnormalities. Once the basic technique and appearances are
mastered, disease detection and management can be rapid.
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Abstract
Introduction
