is an Associate Professor of Radiology,
is a Professor of Radiology, and
is an Assistant Professor of Radiology, Mayo Clinic,
is a Professor of Radiology, Department of Radiologic Pathology,
Armed Forces Institute of Pathology, Walter Reed Army Medical
Center, Washington, DC.
The opinions or assertions contained herein are the private
views of the authors and are not to be construed as official or
as reflecting the views of the Department of the Army or the
Department of Defense.
The evaluation of elbow pathology continues to advance, in part
because of improved diagnostic imaging techniques. These
improvements have assisted the radiologist in providing more
accurate diagnoses and, therefore, better patient care. A variety
of imaging modalities may be used for the evaluation of the elbow,
depending on the indication and suspected disease process. This
article will provide an overview of the imaging characteristics of
some disease processes that can affect the elbow, such as trauma,
arthropathy, and infection.
Most evaluations of the elbow begin with radiographs because of
their screening value and relatively low cost. Lateral and
anteroposterior (AP) radiographs are essential in the basic
evaluation of disease. Oblique radiographs or additional views,
such as the radial head view, may be utilized for further
evaluation of occult trauma or early arthropathy.
Advancement in technology has allowed multiplanar imaging with
multidetector computed tomography (MDCT). Mulitdetector CT is a
quick means to acquire volumetric imaging data that can then be
reconstructed in an infinite number of imaging planes, including
3-dimensional volume and surface renderings. It is possible to
perform a single scan with thin slices that consist of
near-isotropic voxel dimensions.
Osseous structures are best evaluated using "bone" algorithm
reconstructions, whereas soft tissues and surface-rendered images
are better generated in a "standard" algorithm.
In the presence of metal in the postoperative elbow, increased kVp
and mAs will help decrease metal-induced streak artifact.
Magnetic resonance imaging (MRI) of the elbow can clearly define
normal bone, soft tissue anatomy, and pathology.
Dedicated circumferential elbow surface coils, small field of view
(10 to 12 cm), and high-field-strength magnets provide optimal
image quality. Image planes and field of view for the elbow vary
with study indication and include axial, sagittal, and coronal;
oblique and reformatted thin-section gradient-echo images are
The axial image plane is useful to assess neurovascular, tendon,
and muscle anatomy. The sagittal plane is useful as a second plane
for biceps and triceps tears or to define the extent of a lesion
identified on axial images. The coronal plane is useful for
evaluating articular surfaces, common extensor and flexor tendons,
and collateral ligaments.
Methods for decreasing metallic susceptibility artifact in the
postoperative patient include increasing the bandwidth, aligning
the metal along the long axis of the magnet bore, utilizing fast
spin-echo sequences, avoiding fat suppression, orienting the
frequency- encoding direction along the main longitudinal axis of
the implanted hardware, and increasing the frequency-encoding
Elbow arthrography-either conventional, or followed by CT or
MRI-is helpful in diagnosing capsular and ligament tears,
osteochondral lesions, and loose bodies when there is no joint
The elbow can be injected laterally (radiocapitellar joint) or
posteriorly with 8 to 12 mL of solution. Using a 50% diluted
iodinated contrast solution for CT arthrography should not obscure
small loose bodies. A 1:250 diluted gadolinium solution that
contains 50% lidocaine/bupivacaine and 50% iodinated contrast can
be used for MR arthrography. Following injection, T1-weighted (T1W)
fat-suppressed images are obtained in the axial, coronal, and
sagittal planes. In addition, a fast spin-echo (FSE) T2-weighted
(T2W) fat-suppressed (FS) sequence is obtained for the detection of
marrow abnormalities, soft tissue lesions, or fluid
Sonography is useful in evaluating a variety of structures, such
as the common extensor and flexor origins, collateral ligaments,
nerves, and bursae.
Medium- (7.5 MHz) or high-frequency (12 MHz) linear array
transducers can provide high-resolution images of the periarticular
In experienced hands, this modality has been proven to be quite
Nuclear medicine imaging is occasionally used for imaging elbow
pathology. Bone scintigraphy with technetium-99m methylene
Tc-MDP) is helpful to identify areas of active bony turnover and
reparative processes. Combined
Tc-MDP and indium-111
In)-labeled leukocyte scans can be useful in the detection of
infection, and fluorine-18-fluordeoxyglucose (FDG) positron
emission tomography (PET) imaging can identify foci of
hypermetabolic activity in cases of tumor, inflammation, and
Elbow fractures and other injuries are common in infants,
children, adolescents, and adult throwing athletes.
Routine radiographs and CT are generally sufficient for the
detection and classification of skeletal injuries. However, it is
not uncommon to detect occult skeletal injuries with MRI that were
overlooked or were not identifiable with conventional techniques.
In children, supracondylar humeral fractures account for 50% to 60%
of all fractures and have high complication rates.
Physeal fractures are also common in children and adolescents, with
the majority of injuries occurring between 4 and 8 years of age,
when epiphyses are not well ossified.
Fractures of the lateral condyle are most common, accounting for
>54% of fractures.
"Little leaguer's elbow" typically occurs in 9- to 12-year-old
baseball pitchers, and represents avulsion and fragmentation of the
medial humeral epicondyle due to repeated valgus stress from the
flexor and pronator muscles across the growth plate.
The radial head fracture is the most common elbow fracture in
adults. Trauma evaluation should begin with radiographs (Figure 1)
but may be supplemented with CT or MRI. Imaging features that
affect patient prognosis include the degree of comminution,
angulation, and depression of the radial head fracture. CT may be
useful in evaluating the articular congruity of the radial head,
especially after reduction (Figure 2). MRI is very sensitive for
the detection of occult fractures (Figure 3), either in the marrow
Marrow edema or bone contusions are low in signal intensity on T1W
images. Fractures are evident as hypointense lines within the
marrow if there is trabecular compression and discontinuity of
hypointense cortical bone.
Radial head fractures can be classified by the Mason Johnston
Type I include nondisplaced fractures. Type II are minimally
displaced fractures with depression, angulation, and impaction.
Type III fractures are fractures that are comminuted and displaced.
The most severe, Type IV, are radial head fractures that are
associated with dislocation of the elbow. In cases of extensive
comminution of the radial head, radial head resection is usually
performed, allowing for resumption of pronation and supination.
Occasionally, radial head prostheses are placed in the attempt to
gain function. However, these implants are prone to fracture, may
dislodge, or may cause synovitis (Figure 4).
The capitellum is less commonly injured than the radial head.
Fractures often occur from valgus force, with impaction of the
radial head against the capitellum (Figure 5). One known imaging
pitfall is the pseudodefect at the junction of the capitellum and
lateral epicondyle, which is actually a normal osseous groove.
The pseudodefect deepens as images proceed more laterally, and
occasionally 1 or more fine, low-signal lines extend from the
pseudodefect into the marrow.
In adults, dislocations of the elbow are second only to those of
the shoulder in frequency. In children, it is the most common
dislocation. Simple posterior elbow dislocations usually result in
complete disruption of all of the capsuloligamentous structures,
with variable adjacent muscular injury.
Persistent instability after closed reduction of a simple
dislocation may be secondary to soft tissue interposition or
entrapment of an intra-articular chondral or osteochondral
MRI and MR arthrography may assist in diagnosis in these
circumstances. Fracture-dislocations take various forms in the
elbow and forearm. The Monteggia fracture-dislocation is composed
of a fracture of the proximal ulnar and a dislocation of the radial
head (Figure 6). Care must be taken not to overlook subtle
subluxations or nondisplaced fractures with this injury
Radiographs may exhibit irregularity of the radial tuberosity in
chronic biceps tendon injuries, obliteration of the supinator fat
stripe, or, rarely, acute avulsion fractures.
MR imaging is ideally suited to evaluate injuries of the biceps
tendon. T2-weighted, gradient-echo, or short tau inversion recovery
(STIR) images are best for showing the high signal abnormality of
hemorrhage as well as the inflammation and fluid seen against the
normal low signal intensity of the tendon.
The distal biceps tendon is the most commonly injured tendon in the
elbow. Ruptures of the biceps tendon (Figure 7) account for only 3%
of biceps injuries and are most common in men >40 years of age.
Injuries typically occur at or near its insertion into the radial
tuberosity as a result of forced hyperextension with the arm flexed
Tendon ruptures are characterized by complete discontinuity of the
tendon, increased intratendinous signal, peritendinous
fluid/hematoma, and muscle and tendon retraction.
The tendon does not retract if the bicipital aponeurosis (lacertus
fibrosis) remains intact. Partial tears (Figure 8) are visible on
MR as thinning, increased intratendinous signal, peritendinous
fluid, and, occasionally, a proximally thickened tendon.
Although inflammation of the triceps is fairly common, ruptures
of the triceps tendon are rare (Figure 9).
Radiography is useful in evaluating triceps injury, since up to 80%
of patients will have avulsion fractures of the olecranon.
Inflammation in the muscle or tendon is evident as irregular areas
of increased signal intensity on fluid-sensitive MR images.
Complete disruption results in areas of high signal intensity
separating the low-intensity tendon fragments.
The triceps tendon normally has striations of increased signal that
insinuate between the distal tendon fibers and should not be
mistaken for tears.
Common extensor and flexor tendons
Tendinopathy or tears of the common extensor and flexor tendons
can be evaluated with MRI or sonography.
Typically, imaging studies are not performed unless the patient has
failed conservative treatment.
In patients with lateral tennis elbow, the primary site of
involvement is the common extensor tendon origin. MRI reveals
thickening and intermediate signal within the tendon origin in
cases of tendinopathy. Partial tears are depicted by thinning or
partial disruption of the tendon, and increased T2W signal within
and adjacent to the tendon origin (Figure 10). Complete rupture of
the tendons will lead to a tendinous gap containing fluid signal,
and distal retraction of the involved muscle(s). Dystrophic
calcifications can arise adjacent to the lateral epicondyle and are
best depicted on gradient-echo images.
Lateral epicondylitis is evident as a focal hypoechoic area in the
deep part of the tendon or a discrete cleavage plane with
Injuries to the common flexor tendon origin (golfer's elbow or
medial tennis elbow) (Figure 11) are less common than injuries of
the common extensor tendon origin.
Common flexor tendon injury occurs at the origins of the flexors
and pronator teres.
This syndrome occurs in 1% to 3% of adults who are 35 to 55 years
of age, and it is often seen in golfers, high-performance throwers,
swimmers, racketball and squash players, and bowlers.
MR arthrography has been advocated for the detection of partial
The diagnosis of partial tears is critical to throwing athletes,
because these patients will likely undergo surgery.
Radial (lateral) collateral ligament complex
Additional support for the elbow is provided by the radial and
ulnar collateral ligament complexes.
The radial (lateral) collateral ligament (RCL) complex is composed
of the lateral ulnar collateral ligament, RCL proper, and the
annular ligament (Figure 12).
Injury to the RCL complex (Figure 13) is less common than medial
ligament injury and is usually the result of varus stress or
subluxation/ dislocation. Overly aggressive surgical procedures,
such as common extensor tendon release or radial head resection,
can also lead to radial collateral ligament injury.
The lateral ulnar collateral ligament is the primary stabilizer
against varus stress, and its disruption (Figure 14) can lead to
posterolateral rotatory instability of the elbow.
The radial collateral ligament proper attaches to the annular
ligament; therefore, both structures should be evaluated
Ulnar (medial) collateral ligament complex
The ulnar (medial) collateral ligament consists of 3 bands and
is much stronger than the RCL (Figure 15). The anterior band is the
dominant structure and the primary stabilizer against valgus stress
on the elbow.
It courses anteriorly from the anteroinferior surface of the
epicondyle and attaches to the medial edge of the coronoid process.
The posterior band is smaller and has a fanlike configuration.
It extends from behind the medial epicondyle and courses slightly
posteriorly to attach onto the medial aspect of the olecranon. The
transverse band is clinically less significant, is smaller or
sometimes absent, and is often difficult to identify on MR.
Acute ruptures are not a diagnostic dilemma and are seen as
discontinuity and an abnormal course of a ligament. Partial tears
(Figure 16) are more difficult to diagnose with imaging;
articular-surface tears are more accurately assessed with MR
MRI is not required for the diagnosis of osteoarthrosis.
However, since it is such a common disorder, osteoarthrosis is
often imaged in patients with other diagnostic dilemmas. The
hallmark characteristics of osteoarthrosis (osteophytes, joint
space narrowing, chondromalacia, loose bodies, etc.) are clearly
depicted by multiplanar MR imaging (Figure 17).
Cartilage may be optimally imaged using gradient-echo imaging (such
as double-echo steady state) or with MR arthrography.
Multiple other arthropathies can affect the elbow, some of which
have characteristic features. Gout may also involve the elbow
(Figure 18). The olecranon bursa is more commonly involved than the
joint. Fluid in the bursa may be due to bursitis, but gout should
always be considered.
When the elbow is affected by rheumatoid arthritis, the wrist and
hand are invariably involved.
MRI provides a method for early detection of synovial inflammation
and bone erosions (Figure 19). Response to therapy (active synovial
inflammation and new erosions) can also be monitored with
contrast-enhanced MR imaging.
Musculoskeletal infections may present with an acute, rapidly
progressing course or may be insidious. Determining the extent of
involvement is important in planning medical or surgical
management. For example, the quantity of fluid within an infected
olecranon bursa and the extent of the surrounding soft tissue
involvement can be delineated with CT (Figure 20). Osseous
involvement with infection is first assessed with radiographs
(Figures 21 and 22), which may be diagnostic. Radioisotope studies
(Figure 21) are particularly sensitive in the early stages of
infection. The anatomic extent, however, may be inaccurate,
especially in the articular regions, and differentiation of
cellulitis or soft tissue infection from bone involvement is not
MR imaging may be required to make a definitive diagnosis of
infection. Generally, a combination of T1W, STIR, or FSE T2W
fat-sup-pressed, and enhanced T1W fat-suppressed images is the most
sensitive technique for the detection of osteomyelitis.
Osteomyelitis is characterized by an area of prolonged T1 and T2
relaxation times and marrow en-hancement. Changes in cortical bone
(osteitis), periosteum (periostitis), and muscle are often less
obvious. The presence of associated cortical destruction, sinus
tracts, low-intensity sequestra, cloaca, and adjacent soft tissue
inflammatory signal changes can also be evaluated with MR.
In this article, the imaging characteristics of a variety of
disease processes involving the elbow have been presented. There
are distinct advantages of each of the different imaging
modalities: radiography, sonography, scintigraphy, arthrography,
CT, and MRI. The choice of imaging technique will depend on the
suspected disease process, the availability of advanced imaging
(such as MDCT and MRI), and the personal preference of the
radiologist. The ultimate goal is to provide the most accurate
diagnosis for each patient, which allows for the best patient