Question 1

A. Correct! Osteochondritis dissecans (OCD) on magnetic resonance imaging appears as a focal well-circumscribed osteochondral lesion at the epiphysis, frequently occurring in the knee at the lateral aspect of the medial femoral condyle. This is also sometimes termed an osteochondral lesion.

Other choices and discussion

B. Jumper’s knee is a chronic insertional injury of the proximal attachment of the patellar tendon, presenting as thickening and increased signal within the tendon and bone marrow edema in the adjacent patella.

C. The visualized medial collateral ligament is intact.

D. No meniscal tear is demonstrated.

E. A Salter Harris type II fracture would pass across the growth plate and through the metaphysis. The growth plates and metaphyses in this patient are intact.

Question 2

A. Correct! Patients with OCD lesions tend to be young (under 18 years) and are twice as likely to be male.

D. Correct! Although the exact cause is unknown, OCD is thought to be secondary to an injury of an ossification center in the epiphyseal cartilage.

E. Correct! Surgical treatment options for unstable OCD lesions include microfracture, pinning of the osteochondral lesion, and osteochondral grafting (autograft or allograft).

Other choices and discussion

B. OCD most commonly affects the knee. It can also be seen in the talar dome of the ankle and in the capitellum of the elbow.

C. In the knee, osteochondral lesions are most frequently seen in the lateral aspect of the medial femoral condyle (70%). Lateral condylar lesions are the next most frequent (10 to 20%). Patellar lesions account for 5 to 10% of cases, and trochlear lesions are rarely seen.

Question 3

A. Correct! A T2 hyperintense (fluid intensity or granulation tissue intensity) rim surrounding an OCD lesion suggests instability in adults. However, because osteochondral lesions frequently heal with conservative management in juvenile patients, the criteria are stricter, and this rim must be fluid signal. The presence of cysts (even one) surrounding an OCD lesion in an adult is consistent with instability, but in a juvenile patient, the cysts should be > 5 mm in size and multiple in number to suggest instability. But even in the latter scenario, some lesions will go on to heal without surgical intervention.

B. Correct! Low-signal intensity rim or cortication around the lesion suggests instability. This would have a similar appearance to chronic ununited fractures elsewhere in the body, with the low signal cortication seen on the opposing surfaces of both the lesion and the parent bone.

C. Correct! Fragmentation of the subchondral plate suggests instability.

D. Correct! Displacement or dislocation of the fragment suggests instability.

Incorrect choice and discussion

E. A bone marrow edema pattern may be seen within the lesion or the donor site in the setting of an OCD. However, this alone is not a sign of instability.

Question 1

B. Correct! This is a Lisfranc fracture-dislocation. Offset of the second tarso-metatarsal (TMT) joint is the result of a Lisfranc ligament injury. The Lisfranc ligament runs from the second metatarsal base to the medial cuneiform. Lisfranc fracture-dislocations are divided into homolateral, in which the first through fifth metatarsals are displaced laterally, and divergent, in which the second through fifth metatarsals are displaced laterally but the first metatarsal is displaced medially. Complete Lisfranc fracture-dislocations involve all five metatarsals. In the test case, the first metatarsal base is fractured and dislocated medially. This is an example of an incomplete divergent Lisfranc fracture-dislocation. Disruption of the Lisfranc ligament typically occurs with midfoot plantar flexion in low impact trauma and with direct force in high impact trauma (i.e., motor vehicle accident).

Other choices and discussion

B. The second metatarsal base is not fractured.

C. This patient has an unremarkable past medical history and presents with an acute injury, making neuropathy unlikely. Note that neuropathy can predispose to a Lisfranc ligament injury. This is often seen in diabetic patients, may be clinically silent, and may result in midfoot arthritis and pes planus.

D. The Chopart joint refers to the calcaneocuboid and talonavicular joints. These are normal in the test case.

E. A midfoot sprain refers to Lisfranc ligament sprain without disruption of the second TMT joint. The test case demonstrates a more serious injury.

Question 2

C. Correct! The Lisfranc ligament has three components: dorsal, interosseous, and plantar. All connect the base of the second metatarsal to the medial cuneiform. The dorsal band is the weakest, explaining the frequent dorsal dislocation of the second metatarsal base with a Lisfranc ligament rupture. Weight-bearing views of the foot are very useful in depicting this dorsal dislocation.

Question 3

A. Correct! A Lisfranc fracture-dislocation or Lisfranc ligament injury that is unstable or displaced can lead to osteoarthritis and midfoot collapse if not surgically repaired in anatomic alignment.

Other choices and discussion

B. The more conservative treatment of closed reduction puts the patient at a greater risk for subsequent morbidity.

C. The more conservative treatment of placing the patient in a walking boot puts the patient at a greater risk for subsequent morbidity.

D. Repeating the radiograph is unlikely to add useful information, as the diagnosis is made on the initial radiographs.

E. Ultrasound may detect a tear of the Lisfranc ligament. However, because the radiograph already shows a Lisfranc fracture-dislocation, ultrasound is not needed. Some surgeons use computed tomography or magnetic resonance imaging for preoperative planning and to assess for additional radiographically occult fractures that can accompany Lisfranc injuries.

Question 1

A. Correct! A small bony fragment adjacent to the ulnar base of the thumb proximal phalanx is seen. This indicates an ulnar collateral ligament (UCL) avulsion fracture. This has been classically referred to as a “gamekeeper’s thumb,” referencing chronic UCL injuries in patients who repetitively broke the necks of small game (rabbits). Today, this injury is most commonly seen with skiers (although “skier’s thumb” is considered more of an acute injury by some). The fracture fragment in this case is displaced and rotated. The thumb metacarpophalangeal joint may be in valgus angulation with radial subluxation of the proximal phalanx.

Other choices and discussion

B. The radial collateral ligament attaches to the radial aspect of the proximal phalanx and, if injured, results in an avulsion fragment at that site and/or ulnar subluxation of the proximal phalanx.

C. Pulley injuries rarely result in avulsion fractures and therefore are typically radiographically occult.

D. An extensor tendon injury is not present in the test case. A dorsal avulsion fracture and a fixed flexion deformity could represent an extensor tendon injury.

E. A flexor tendon injury is not present in the test case. A volar avulsion fracture and a fixed extension deformity could represent a flexor tendon injury.

Question 2

C. Correct! Stress views should never be performed in patients with a gamekeeper’s thumb, as stress views can actually create a Stener lesion and transform a nonsurgical injury into a surgical injury. A Stener lesion is present when the torn UCL is abnormally displaced over the adductor aponeurosis/adductor pollicus tendon. This alignment will prevent normal ligament healing, and therefore a Stener lesion requires surgical fixation.

Other choices and discussion

A. Magnetic resonance imaging (MRI) is helpful in evaluating the extent of injury to the UCL and in assessing for a possible Stener lesion. A UCL injury can often be very subtle or occult on initial radiographs.

B. Surgical fixation is required in the presence of a Stener lesion. In this case, the displaced and rotated fracture fragment is concerning for the presence of a Stener lesion. This was subsequently proven surgically, as the patient underwent surgical reduction and fixation of the UCL and avulsion fragment.

D. Conservative management (immobilization and pain control) is often sufficient to treat a nondisplaced UCL tear. However, when a Stener lesion is present, or when conservative management has failed, surgical fixation is required.

E. Like MRI, ultrasound is helpful in evaluating the extent of injury to the UCL and in assessing for a possible Stener lesion. Musculoskeletal ultrasound is often a dynamic examination, but for this indication, dynamic imaging should either be avoided or performed very carefully to avoid causing a Stener lesion.

Question 3

B. Correct! The UCL is injured when the thumb undergoes extreme hyperabduction. Gamekeeping, skiing, and break dancing have all been implicated as risk factors.

Other choices and discussion

A. A hyperadduction injury would not injure the UCL. (An injury to the radial collateral ligament would be more likely with that mechanism.)

The other mechanisms would not typically account for an injury to the UCL.

Question 1

D. Correct! The sacroiliac (SI) joints are fused bilaterally, consistent with chronic bilateral sacroiliitis. The cervical spine radiograph shows multilevel thin, bridging syndesmophytes, consistent with a “bamboo spine.” This presentation is typical of ankylosing spondylitis, a seronegative spondyloarthropathy with a strong HLA-B27 antigen association. “Seronegative” refers to the absence of rheumatoid factor.

Other choices and discussion

A. Psoriatic arthritis is associated with bulky paravertebral ossification, not thin flowing syndesmophytes, as in the test case. Psoriatic arthritis is commonly associated with asymmetric bilateral sacroiliitis, although in chronic cases, sacroiliitis may become more symmetric.

B. Diffuse idiopathic skeletal hyperostosis is associated with multilevel bulky ossification of the paraspinal ligaments, not thin flowing syndesmophytes. Diffuse idiopathic skeletal hyperostosis is usually considered an incidental finding and is not associated with sacroiliitis, although the SI joints can be fused superiorly by bulky bridging bone, similar in appearance to that seen in the spine.

C. Reactive arthritis (formerly known as Reiter syndrome) is typically associated with asymmetric bilateral sacroiliitis, although in chronic cases, sacroiliitis may become more symmetric. In the spine, reactive arthritis is associated with bulky paravertebral ossification, not thin flowing syndesmophytes.

E. Inflammatory bowel disease is associated with arthropathy, and its radiographic appearance can be similar to that of ankylosing spondylitis. However, because this patient had no gastrointestinal symptoms, inflammatory bowel disease arthritis is unlikely.

Question 2

C. Correct! The enthesis is the primary site of disease in ankylosing spondylitis and represents the connective tissue between a tendon or ligament and bone. Because the SI joints are predominantly lined with fibrocartilage and with very little synovial tissue, these joints can be thought of as entheses, explaining their characteristic involvement in spondyloarthropathies such as ankylosing spondylitis. Chronic inflammation of an enthesis can lead to subsequent ankylosis. Patients with ankylosis are at an increased risk for developing fractures.

Sacroiliitis is usually the first site involved by ankylosing spondylitis. This disease affects the spine and hips, and can also affect the shoulders, knees, hands, and the lung parenchyma (with apical predominant fibrobullous changes).

Other choices and discussion

B. The synovial membrane is the primary site of disease in rheumatoid arthritis, not ankylosing spondylitis.

The other choices are incorrect.

Question 3

C. Correct! The thoracolumbar junction is the most common site of a Romanus lesion. A Romanus lesion is a focal inflammatory erosive area along the anterior superior or anterior inferior margin of a vertebral body and can be seen early in the course of spondyloarthropathies. With magnetic resonance imaging, they show focal short tau inversion recovery hyperintensity during active inflammation. Later, these lesions may become sclerotic as they heal, leading to the “shiny corner” sign. They can also leave behind postinflammatory fatty marrow (without short tau inversion recovery hyperintensity).

Discussion

Regarding the SI joint, there are several mimics of true sacroiliitis. Hyperparathyroidism can cause erosion and mimic bilateral sacroiliitis. Osteitis condensens ilii is not a true sacroiliitis. This refers to benign sclerosis of the ilium as it borders the SI joint. This is often triangular in shape. Diagnosis can be made when this finding is seen with a lack of involvement of the adjacent sacrum and preservation of the SI joint space. This is usually asymptomatic.

Only the lower half of the SI joint represents a true diarthrodial joint. Scrutinize the lower half of the SI joint carefully when assessing for arthropathy.

Question 1

C. Correct! The central endplate depression seen in multiple vertebral bodies is typical of sickle cell disease. The biconcave endplates in the test case result in a “fish mouth” appearance. The more characteristic “H shaped” or “Lincoln log” vertebrae may be seen later as the endplate infarcts progress.

Other choices and discussion

A. Paget disease in the spine is characterized by dense sclerosis and overgrowth of the vertebral body.

B. Hyperparathyroidism in the spine produces transverse vertebral body endplate sclerosis, likened to a rugby or “rugger” jersey. If there are superimposed endplate insufficiency fractures, the vertebrae may take on a fish mouth appearance. No endplate sclerosis is present in the test case, however.

D. Osteopetrosis in the spine causes dense vertebral body endplate sclerosis, resulting in a “sandwich” vertebra.

E. Renal osteodystrophy in the spine results in a similar appearance to that of hyperparathyroidism.

Question 2

B. Correct! The vertebral body central endplate depression in sickle cell disease is caused by bone infarcts.

Discussion

Sickle-cell disease is an autosomal recessive condition characterized by abnormally shaped red blood cells. Its impact is extensive throughout the body, and it results in considerable morbidity and mortality. Typical radiographic findings include the vertical “hair-on-end” appearance of the calvarium, H-shaped or “fish-mouth” vertebrae, diffuse osteopenia, and coarsening of the trabeculae in the long bones.

Associated persistence of red marrow in the long bones and additional sites of red marrow reconversion are seen on magnetic resonance imaging. Marrow expansion is also detected on bone scintigraphy. Patients with sickle cell disease are predisposed to both infarcts and osteomyelitis.

Question 3

A. Correct! Patients with sickle cell disease have an increased incidence of osteomyelitis and septic arthritis because of bone infarcts and hyposplenism. Hyposplenism reduces the body’s ability to eradicate certain bacteria. Salmonella infections are particularly common with sickle cell patients.

B. Correct! Impaired growth occurs subsequent to bone infarcts, which affect the epiphyses and growth plates.

C. Correct! Although extramedullary hematopiesis occurs more in thalassemia and hemolytic anemias, it can also be seen with sickle cell disease, resulting in osseous expansion and soft tissue masses in the chest, adrenal glands, and skin.

E. Correct! Sickle cell disease causes venous stasis and tissue hypoxia, which produces skin ulceration, particularly over bony prominences.

Incorrect choice and discussion

D. There is no conclusive evidence for an increased risk of musculoskeletal malignancy with sickle cell disease. Renal medullary cancer, a rare and aggressive neoplasm of the kidney, is associated with sickle cell trait.

Question 1

B. Correct! There is focal globular soft tissue mineralization in the region of the rotator cuff insertion, consistent with hydroxyapatite crystal deposition, or calcific tendinosis.

Other choices and discussion

A. A greater tuberosity fracture would have bone matrix, not amorphous calcium as is shown in the test case.

C. A frozen shoulder (or adhesive capsulitis) is characterized by thickening and contraction of the joint capsule and synovium of the shoulder. The plain film is typically normal. Magnetic resonance imaging sometimes shows capsular thickening and high signal in the axillary recess, and intermediate signal in the rotator interval.

D. A chondroblastoma is typically a well-defined lucent lesion seen in young patients (younger than age 20 years), localized to the epiphysis of a long bone. The test case demonstrates several small lucent lesions with sclerotic rims in the humeral head. However, these are typical of benign enthesopathic intraosseous cysts.

E. There is no humeral neck fracture. There is a mild humeral head osteophyte formation, which can sometimes mimic a fracture.

Question 2

A. Correct! Calcific tendinosis most commonly affects the shoulders, and in particular the rotator cuff. These calcific deposits may also occur in the wrists, elbows, hands, hips, knees, and feet.

Within the rotator cuff, the distribution breakdown is as follows: supraspinatus (80%), infraspinatus (15%), and subscapularis (5%).

Question 3

A. Correct! Calcific deposits can shed into the overlying subdeltoid bursa, causing inflammation and pain, which may be severe.

C. Correct! Both Doppler hyperemia and subdeltoid bursal distention correlate with pain in calcific tendinosis.

D. Correct! There are formative, resting, and resorptive phases. During the formative phase, calcium crystals coalesce within the tendon to form a calcific focus. During the resting phase, fibrocartilaginous tissue encapsulates the calcific focus. During the resorptive phase, there is spontaneous resorption of the calcium, which generates an inflammatory response that is often characterized by an acute pain syndrome and limited range of motion.

E. Correct! During the resorptive phase, the calcium is shed into the overlying subdeltoid bursa and can erode into bone, causing inflammation. On magnetic resonance imaging, these inflammatory changes can appear very aggressive and raise suspicion for infection or malignancy. Bony erosion can also appear aggressive on computed tomography. Ultrasound and radiographs are recommended for the imaging evaluation of calcific tendinosis, given the typical appearance on these modalities and the relatively low cost.

Other choice and discussion

B. The main treatment is NOT surgical resection. Treatment options for rotator cuff calcific tendinosis include ultrasound-guided aspiration/lavage and subacromial-subdeltoid bursal corticosteroid injection. These have a high treatment success rate. Refractory cases may undergo surgical resection, but this is uncommon.

Question 1

A. Correct! Magnetic resonance images reveal an anterior patellar cortex osseous erosion, with defined sclerotic margins and overhanging edges, giving the appearance of a “rat-bite.” The soft tissue material in the bed of the erosion is of intermediate signal. These findings are typical for a gouty tophus.

Other choices and discussion

B. A torn quadriceps tendon at the distal-most insertion on the patella would have the abnormality centered at the tendon (with discontinuity of fibers and intrinsic high signal), rather than centered at the bone, as in this case. If present, a complete quadriceps tendon tear would retract the patella in a distal direction (“patella baja”).

C. Patellar enthesopathy is seen as osseous proliferation or spurring at the quadriceps or patellar attachments. It involves inflammation at sites where ligaments, tendons, or joint capsules attach to the bone. Enthesopathy would not be associated with erosions.

D. Erosions associated with rheumatoid arthritis usually occur in the bare areas of synovial joints and do not typically demonstrate the sclerotic margins or overhanging edges seen in gout. Synovitis is the earliest abnormality to appear with rheumatoid arthritis, which is not demonstrated in this case.

E. The lack of an adjacent soft tissue ulcer makes infection less likely than gout. Additionally, an acute infection is unlikely to produce an intraosseous lesion with such well-defined margins. However, infection in soft tissue often affects adjacent bone—for example, direct extension from a foreign body is possible—and infection would be a diagnostic consideration.

Question 2

B. Correct! Approximately 50% of the cases of gout occur at the medial aspect of the first metatarsal head. Gout is found in the ankles (Achilles), feet (intertarsal joints), wrists (carpometacarpal compartment), in entheses around the knees (patellar and popliteus tendons), shoulders, and sacroiliac joints. Bilateral olecranon effusions may be seen and are a clue to the correct diagnosis.

All other choices are incorrect.

Question 3

A. Correct! Marginal osseous erosions with sclerotic margins and overhanging edges occur late in the disease process. Most early presentations of gout have normal plain films.

B. Correct! Sonographic features of gout include joint effusion, as well as echogenic deposits in the joint fluid, the synovium, and/or the cartilage surface. Ultrasound is very sensitive for detecting joint fluid and is also capable of visualizing fine echogenic deposits.

Other choices and discussion

C. Tophaceous deposits are not restricted to intra-articular locations.

D. Dual energy CT has demonstrated a sensitivity and specificity of up to 100% and 95%, respectively, for the diagnosis of gout. However, frequent use of urate lowering therapy may decrease the sensitivity for diagnosing gout with dual energy CT.

E. Tophi have usually do not the typical T1 hypointense, T2 hyperintense appearance of most masses. On magnetic resonance imaging, tophi are usually T1 and T2 isointense and demonstrate prominent enhancement. There may be variable signal, depending on the amount of calcium.

Question 1

B. Correct! Discoid meniscus (which is seen in the lateral meniscus of the test case) is thought to represent a multifactorial congenital condition in which the center of the meniscus contains extra meniscal tissue. Despite the extra meniscal tissue, the meniscus is more prone to injury than a normal meniscus. A discoid meniscus may be fully or partially discoid, both of which produce an abnormally thickened and enlarged morphology. A discoid meniscus is often hypermobile, predisposed to injury, and places the patient at an increased risk for knee instability.

Other choices and discussion

A. Osteophytes form as the result of osseous remodeling, typically seen in response to cartilage loss in a joint. If large enough, osteophytes may result in soft tissue impingement or a clicking sensation. Osteophytes would not predispose to joint instability.

C. The medial collateral ligament is slightly thickened, but there is no discontinuity of fibers, no adjacent inflammation, and no evidence for a tear. The thickening in this case may be the result of nonacute altered weight bearing or prior sprain.

D. No obvious bone bruise is present, although fluid-sensitive sequences would be needed to exclude this type of microtrabecular injury. Even if present, a bone bruise would be painful but would not predispose to joint instability.

E. An anterior cruciate ligament tear would predispose the knee to instability, but the anterior cruciate ligament appears intact based on the coronal image.

Question 2

A. Correct! The discoid meniscus is hypermobile and may be devoid of peripheral attachments, predisposing to injury.

B. Correct! The incidence of discoid meniscus is much higher for the lateral meniscus than for the medial meniscus.

D. Correct! There are decreased collagen fibers and loss of normal collagen orientation in a discoid meniscus, and mucoid degeneration is common. Additionally, discoid menisci are more susceptible to injury than normal menisci, as their abnormal shape and thickness results in increased biomechanical stress.

Other choices and discussion

C. Discoid meniscus is a multifactorial congenital condition, not acquired.

E. A discoid meniscus is often bilateral (up to 50%).

Question 3

A. Correct!

B. Correct! This is seen on the coronal images.

C. Correct! Discoid menisci are predisposed to degeneration, which presents as diffuse intrasubstance high signal on MRI.

E. Correct! When discoid menisci are torn or unstable, surgical treatment is considered. Arthroscopic treatment commonly includes saucerization and debulking of the meniscus to restore a normal shape and to stabilize the meniscus, if there is meniscal instability upon probing.

Other choice and discussion

D. The presence of a meniscal tear disrupts the standard meniscal signal and morphology, and somewhat decreases the ability of MRI to accurately diagnose a discoid meniscus.