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Classic Signs and Findings in Musculoskeletal Radiology
Condition
Absent in posterior dislocation of the shoulder
Name of Sign
Half-moon sign
Description
The medial humeral head normally overlaps the posterior glenoid rim on a standard anteroposterior (AP) shoulder radiograph in external rotation, an appearance resembling a half-moon. When a patient has a posterior shoulder dislocation, there is often no overlap (rim sign).
Condition
Acetabular retroversion
Name of Sign
Figure of 8/crossover sign
Description
On an AP radiograph of pelvis, the anterior acetabular line (black arrows) courses in an S-shaped configuration, traveling lateral to the posterior line (white arrows) superiorly and becoming more medial inferiorly. It intersects the posterior acetabular line along its mid course.
Condition
Anterior cruciate ligament (ACL) mucoid degeneration
Name of Sign
Celery stalk sign
Description
On sagittal fluid-sensitive MR images, the ACL is thickened and higher in signal than expected. However, it maintains normal orientation and contains linear low–signal-intensity foci along the long axis of the ligament that represent intact ligament fibers. The bright signal with intact fibers is commonly attributed to mucoid degeneration.
Condition
ACL reconstruction with focal arthrofibrosis
Name of Sign
Cyclops lesion
Description
Following knee ACL reconstruction, a soft tissue nodule in the intercondylar notch anterior to the tibial tunnel may develop. This may encroach on Hoffa's fat pad and limit joint extension. The Cyclops lesion is most commonly detected on sagittal MR imaging as a nodular structure that is isointense to hypointense to skeletal muscle on T1 imaging. It may be heterogeneous and have variable signal intensity on T2 imaging.
References
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Jackson DW, Schaefer RK: Cyclops syndrome: loss of extension following intra-articular anterior cruciate ligament reconstruction. Arthroscopy 1990; 6: pp. 171-178.
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Recht MP, Piraino DW, Cohen MA, et. al.: Localized anterior arthrofibrosis (cyclops lesion) after reconstruction of the anterior cruciate ligament: MR imaging findings. AJR Am J Roentgenol 1995; 165: pp. 383-385.
Condition
ACL tear (MR)
Name of Sign
Anterior drawer sign
Description
On a mid-sagittal MR image through the lateral compartment of the knee, there should be no greater than 5 mm anterior displacement of the posterior cortical margin of the femoral condyle compared with the tibial plateau using parallel plumb lines along the long axis of the image.
Condition
ACL tear (radiographs and MR)
Name of Sign
Deep lateral femoral notch sign
Description
On a lateral knee radiograph or sagittal MR image that includes the lateral femoral condylar sulcus terminalis, a tangent line is drawn to the lateral femoral condyle and the distance between the line and apex of the roof of the sulcus is measured. This should be no greater than 1.5 mm.
Condition
ACL tear (MR)
Name of Sign
Posterior cruciate ligament (PCL) sign
Description
On sagittal MR images of the knee, a line drawn parallel to the posterior margin of the posterior cruciate ligament that fails to intersect the distal femoral medullary cavity within 5 cm of the distal femur indicates anterior tibial subluxation and is commonly seen in the setting of an ACL tear.
Condition
ACL tear—Segond fracture, healed
Name of Sign
Bock Bosch sign
Description
On radiographs of the knee, there is a characteristic osseous excrescence 3-6 mm inferior to the lateral tibial plateau seen at the site of previous Segond fracture. As in the acute Segond fracture, the presence of this excrescence implies internal derangement of the knee.
Condition
Acromegaly
Name of Sign
Heel pad sign
Description
On lateral radiographs of the ankle, the shortest distance between the plantar aspect of the calcaneus and skin surface is measured. 21 mm is the top normal distance if there is no other explanation for this finding (i.e., infection, generalized edema). Obesity can influence the heel pad thickness.
Condition
Adductor aponeurosis injury
Name of Sign
Secondary cleft sign
Description
On MRI of the pubic symphysis, any fluid signal extending lateral to midline or inferior to the pubic symphysis is termed a secondary cleft. This is a marker for pubic symphyseal pathology such as osteitis pubis or findings of athletic pubalgia.
Condition
Aneurysmal bone cyst
Name of Sign
Fluid-fluid level
Description
Generally detected on fluid-sensitive axial MR sequences, fluid-fluid levels within an expansile osseous lesion are most commonly seen in aneurysmal bone cysts. They can also be seen in telangiectatic osteosarcoma, giant cell tumor, or chondroblastoma.
Condition
Ankylosing spondylitis
Name of Sign
Bamboo spine
Description
On both AP and lateral radiographs, when the spine resembles a stalk of bamboo it often indicates ankylosing spondylitis. This is because of the vertebral body squaring and continuous syndesmophytes causing ankylosis of the spine.
Condition
Ankylosing spondylitis
Name of Sign
Trolley-track sign
Description
On an AP radiograph of lumbar spine, there are three parallel lines of ossification extending along the long axis of the spine. The central line represents ossification of the interspinous ligaments (dagger sign), whereas the lateral lines are related to ossification of the apophyseal joint capsule.
Condition
Ankylosing spondylitis
Name of Sign
Shiny corners sign/Romanus lesion
Description
On lateral spine radiographs the shiny corner sign reflects areas of sclerosis at the anterior and/or posterior corners related to healing erosions at discovertebral junctions. The Romanus lesion was initially described on radiographs and reflects erosion during acute osteitis. It can also be seen on MR as an area of discovertebral junction osteitis.
Condition
Ankylosing spondylitis (pseudarthrosis)
Name of Sign
Andersson lesion
Description
The Andersson lesion is an insufficiency fracture of the ankylosed spine, which may occur at the level of a disk as a transdiskal fatigue fracture or at the level of the vertebral body (transvertebral). Such fractures may occur spontaneously or after minor trauma.
Condition
Avascular necrosis with subchondral fracture
Name of Sign
Rim sign
Description
The rim sign is best seen on fluid-sensitive MR sequences as a bright line between two low–signal-intensity bands. The bright line represents fluid at the site of subchondral fracture; the darker bands represent areas of sclerotic/necrotic bone. On T1 imaging, the T2-bright line is intermediate in signal band and located between two darker bands.
Condition
Biceps long head tendinosis, intraarticular
Name of Sign
Hourglass biceps
Description
Initially described on conventional and CT arthrography, there is hypertrophy of the intraarticular segment of the biceps long head tendon that can become entrapped with arm elevation. This is best seen on longer TE sequences on the sagittal oblique or coronal oblique planes.
Condition
Bone abscess (Brodie), subacute or chronic
Name of Sign
Penumbra sign
Description
On T1 non-fat-suppressed, unenhanced MR images of patients with chronic or subacute intramedullary bone abscesses, there may be a slightly hyperintense rim of signal along the periphery of the abscess cavity. This represents a relatively vascularized zone of transition and may help to distinguish between abscess and neoplasm.
Condition
Bone abscess (Brodie), subacute or chronic
Name of Sign
Target sign
Description
On T1 non-fat-suppressed, unenhanced MR images of patients with chronic or subacute intramedullary bone abscesses there are often four layers of different signal intensity. The most central layer represents the abscess cavity and is low in T1 signal and has high signal on fluid-sensitive sequences (arrowhead) . The next layer (inner ring) is isointense to skeletal muscle on T1 imaging and bright on fluid-sensitive sequences (penumbra sign; long arrow ). The third layer (outer ring) is low in signal on all pulse sequences (short arrow) , and the fourth (most peripheral) layer is low in signal on T1 images but variable in T2 signal intensity.
Condition
Bucket-handle tear of the meniscus
Name of Sign
Absent bow tie sign
Description
At 1.5 tesla and 5-mm-thick sections, the body of the meniscus should be seen on two consecutive sagittal images. If the body is seen on only one section or is not seen, it is considered deficient and may be associated with a flipped meniscal fragment (bucket-handle tear).
Condition
Bucket-handle tear of the meniscus
Name of Sign
Double anterior horn sign/double delta sign
Description
On sagittal MR images, the flipped meniscal fragment does not directly sit on top of the anterior horn as in the flipped fragment sign. Rather, it sits posterior to it, giving the appearance of two separate anterior horns.
Condition
Chondroid matrix
Name of Sign
Rings and arcs appearance
Description
Typical chondroid matrix produces enchondral ossification at the periphery of the cartilage lobules. This is often seen best on conventional radiography or CT as completely calcified halos (rings) or incompletely calcified halos (arcs).
References
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Murphey MD, Walker EA, Wilson AJ, et. al.: From the archives of the AFIP: imaging of primary chondrosarcoma: radiologic-pathologic correlation. Radiographics 2003; 23: pp. 1245-1278.
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Sweet DE, Madewell JE, Ragsdale BD: Radiologic and pathologic analysis of solitary bone lesions. Part III: matrix patterns. Radiol Clin North Am 1981; 19: pp. 785-814.
Condition
Chronic renal failure
Name of Sign
Rugger jersey sign
Description
Thoracic and lumbar radiographs reveal horizontal bands of sclerosis involving the superior and inferior vertebral bodies with relative lucency of the central vertebral body. The appearance resembles alternating horizontal stripes of an English rugby jersey.
Condition
Chronic renal failure
Name of Sign
Radial phalangeal resorption
Description
On AP radiographs of the hands in patients with chronic renal insufficiency and secondary hyperparathyroidism, there is often subperiosteal resorption along the radial margins of the second and third middle phalanges.
References
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Camp JD, Ochsner HC: The osseous changes in hyperparathyroidism associated with parathyroid tumor: a roentgenologic study. Radiology 1931; 17: pp. 63.
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Meema HE, Oreopoulos DG, Meema S: A roentgenologic study of cortical bone resorption in chronic renal failure. Radiology 1978; 126: pp. 67-74.
Condition
Clay shoveler's fracture
Name of Sign
Double spinous process sign
Description
On an AP radiograph of the cervical spine, a transverse fracture through the spinous process with mild distraction of the fracture edges causes the appearance of two smaller spinous processes, one immediately on top of the other.
Condition
Congenital rubella, osteopathia striata
Name of Sign
Celery stalk metaphysis
Description
On long bone radiographs, these entities often produce intraosseous vertical sclerotic striations along the long axis of the involved bone from its epiphysis, which resemble the fibers of a celery stalk.
Condition
Craniosynostosis of the coronal suture
Name of Sign
Harlequin eye deformity
Description
AP radiographs of the infantile skull that show a laterally uplifted superior orbital rim suggest craniosynostosis of the coronal suture. This can be seen bilaterally, as in the associated figure, or unilaterally.
Condition
Elbow effusion
Name of Sign
Elbow fat pad sign or sail sign
Description
On a lateral radiograph of the elbow with the joint flexed at 90 degrees, an elevated lucency anterior to the coronoid fossa of the distal humerus and/or any visible lucency posterior to the olecranon fossa indicates the presence of an elbow effusion.
Condition
Eosinophilic granuloma
Name of Sign
Beveled edge sign
Description
Radiographs of the skull depicting the profile of a well-marginated, lucent focus of eosinophilic granuloma often demonstrate unequal involvement of the inner and outer tables. This causes apparent “beveling” of the lesion's margins.
Condition
Eosinophilic granuloma
Name of Sign
Hole-within-a-hole sign
Description
This sign is seen in cases of multifocal eosinophilic granulomatosis in which two lucent lesions of unequal size overlie one another. The smaller lucent focus appears as an area of additional lucency within the larger osteolytic focus.
Condition
Erosive osteoarthritis
Name of Sign
Seagull deformity
Description
The seagull deformity represents central subchondral cortical erosion of the middle phalanges resulting in depression with remodeling of the bases of the distal phalanges. There is also traction osteophyte formation at the capsular attachment, giving the appearance of seagull wings.
Condition
Femoral head trabecular pattern (normal)
Name of Sign
Asterisk or star sign
Description
On axial CT images of the femoral heads, the primary compressive trabeculae and medial primary tensile trabeculae form a normal pattern of regularly spaced, sclerotic bands radiating from the center. Its absence indicates ischemic necrosis of the femoral head.
Condition
Fibrous dysplasia
Name of Sign
Shepherd's crook deformity
Description
Patients with fibrous dysplasia of the femur often have an exaggerated outward bowing of the femoral head, neck, and shaft, producing a varus deformity resembling the curvature of a shepherd's staff.
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