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The Lower Extremity


THE THIGH

The Femoral Head and Hip Joint

FIGURE 7-1, This 2-year-old infant has Perthes disease on his left side. However, the defect in the right femoral head is a developmental variant, not incipient osteochondritis. A, Hips in neutral position. B, Hips in abduction.

FIGURE 7-2, Normal irregular mineralization of the ossification center of the left femoral head. This appearance in a single center in a young infant does not necessarily indicate disease.

FIGURE 7-3, Normal stippled appearance of one ossification center in a 10-month-old infant. Such centers evolve to normal contour with further growth.

FIGURE 7-4, A, B, Bilateral stippled appearance of the capital femoral epiphyses with progression to normal appearance. A, At 18 months of age. B, At 30 months of age.

FIGURE 7-5, Two examples of normal developmental irregularity of the femoral heads in children without hip symptoms. A, A 3-year-old boy. B, A 4½2-year-old boy.

FIGURE 7-6, Double ossification centers for the capital femoral epiphysis. This finding is a normal variant, not an indication of disease.

FIGURE 7-7, Cleft of the proximal femoral epiphysis in a 3-year-old girl.

FIGURE 7-8, Normal asymmetry in size of the ossification centers of the femoral heads, as shown here, is not necessarily indicative of congenital dislocation of the femoral head.

FIGURE 7-9, The femoral notch in two 9-year-old children. This defect is probably cartilaginous, because arthrography shows that it does not communicate with the joint. It may be seen as early as 4 years of age and disappears gradually over the course of months or years.

FIGURE 7-10, Double femoral head notches seen on the left in a 9-year-old child.

FIGURE 7-11, Two examples of the normal irregularity of the acetabular roofs in young children. This appearance is normal between ages 7 and 12 years.

FIGURE 7-12, Normal intrapelvic protrusion of the acetabula. This is a normal phase of development between 4 and 12 years of age.

FIGURE 7-13, The fossa at the entry point of the acetabular nutrient vessels may simulate a lucent lesion of the femoral head.

FIGURE 7-14, Unusually large bilateral fovea capitis, which may be mistaken for osteochondritis dissecans.

FIGURE 7-15, Normal asymmetry of the fovea capitis.

FIGURE 7-16, Simulated destructive lesions of the femoral heads produced by superimposition of the acetabular bone on the femoral head. A, Hips in neutral position. B, Hips in abduction.

FIGURE 7-17, The lucent interval between the anterior (←) and the posterior lips of the acetabulum ( ) may simulate a lucent lesion of the femoral head ( ).

FIGURE 7-18, Ossification centers for the acetabulum, which may simulate fractures of the femoral head, in a 14-year-old boy.

FIGURE 7-19, The “vacuum” phenomenon in normal hips of a 6-month-old child (lower arrows). The upper arrow indicates an accessory ossification center for the transverse process of L5.

FIGURE 7-20, A, B, “Vacuum” phenomenon in the hips of an adult. Note how the radiolucency in A resembles a fracture line.

FIGURE 7-21, Two examples of the unreliability of Shenton's line after the newborn period. A, A 5-month-old infant. B, A 1-year-old child. Note particularly the asymmetry of the lines in A.

FIGURE 7-22, Apparent bulging of the hip “capsule,” suggesting synovitis or hemarthrosis, may be produced by filming of the hip in abduction and external rotation, as in this 6-year-old boy (←). Note normal fat lines on opposite side ( ).

FIGURE 7-23, Plump femoral heads in a 22-month-old infant.

FIGURE 7-24, Note that when a line is drawn along the femoral necks for the detection of slipped capital femoral epiphysis, there is normal variability in the amount of femoral head that is intersected. This variability is illustrated in films of two adolescent boys.

FIGURE 7-25, A, B, Bilateral developmental spurs at the edge of the closed physis in a 30-year-old man, possible remnants of epiphyseal spurs.

FIGURE 7-26, A, Hypertrophic changes at the femoral head may produce an appearance simulating a fracture of the femoral neck. B, C, Simulated fractures of the femoral neck produced by hypertrophic lipping of the femoral head.

The Femoral Neck

FIGURE 7-27, Normal irregularities of the metaphysial margin of the growth plate in early childhood. A, A 4-year-old girl. B, A 5-year-old boy.

FIGURE 7-28, Normal double-contour effect of cortex of the superior aspect of the femoral neck in a 4-year-old boy. This is a common appearance in children of this age.

FIGURE 7-29, The upper femoral notch (←) in a 13-year-old boy. This is probably the same lesion seen in the humeral neck and other metaphyseal sites. The lesion disappears with growth and is of no significance. Note the poor definition of the upper margin of the femoral neck ( ), also a normal appearance at this age.

FIGURE 7-30, An example of the entities described in Figure 7.29 seen here bilaterally in a 12-year-old boy.

FIGURE 7-31, Two additional examples of the upper femoral notch.

FIGURE 7-32, A, B, Probable residua of the upper femoral notches in a 35-year-old woman.

FIGURE 7-33, Normal irregularities and lucencies in the femoral necks of an 11-year-old boy.

FIGURE 7-34, Normal lucencies in the femoral necks of a 16-year-old boy.

FIGURE 7-35, Normal lucencies in the necks of the femora (Ward's triangle), formed by the angle of the trabeculae in the neck of the femur.

FIGURE 7-36, Bilateral localized trabecular radiolucencies in the femoral necks of a healthy 53-year-old woman.

FIGURE 7-37, A, Pseudolesion of right femoral neck in osteoporosis. B, CT shows no lesions.

FIGURE 7-38, Top left, Normal triangular radiolucencies in the femoral necks produced by the heavy trabeculations in the center of the femoral neck and the overlap of the femoral head medially. Top right, This appearance may be asymmetric in its presentation. Bottom left and right, Similar radiolucencies may be seen in the frog-leg projection.

FIGURE 7-39, Trabecular reinforcement of the femoral necks secondary to osteoporosis. These alterations should not be confused with the trabecular changes of Paget's disease.

FIGURE 7-40, Better-defined trabeculation as seen in Figure 7.39 in elderly woman.

FIGURE 7-41, Relative radiolucencies in the femoral necks of an 85-year-old man, produced by the large trabeculations of the femoral neck inferior and medial to the edge of the greater trochanter.

FIGURE 7-42, Radiolucencies produced by overlap of the greater trochanter and the heavy trabeculation of the femoral neck in a 51-year-old man.

FIGURE 7-43, Slight rotation of the right femur produces an apparent lesion in the intertrochanteric region of the right femur.

FIGURE 7-44, Typical juvenile benign cortical defects are occasionally seen in the femoral neck and are of no clinical significance. A, At 7 years. B, Three years later, the lesion is slightly larger.

FIGURE 7-45, Examples of ringlike radiolucencies of the femoral necks with sclerotic borders. These common lesions are apparently of no clinical significance. There is evidence to suggest that they represent a subcortical pit formed by herniation of synovium through the cortical bone.

FIGURE 7-46, Large herniation pit with demonstration on CT scan.

FIGURE 7-47, Large herniation pit. A, Plain film. B, T1-weighted MR image. C, Fat-saturated T2-weighted MR image.

FIGURE 7-48, Examples of bony thickenings of the inferior aspects of the femoral necks, probably caused by ossification of the inferior retinaculum of the synovial capsule. A, B, A 34-year-old woman; C, D1, and D2, A 25-year-old woman.

FIGURE 7-49, A through D, Four examples of the “white line” of the femoral neck, which probably represents the posterior insertion of the joint capsule. This may be confused with a fracture line.

FIGURE 7-50, Localized reinforcement of major trabeculae in a 75-year-old osteoporotic woman that might be mistaken for an insufficiency fracture.

FIGURE 7-51, A, Normal area of radiolucency of the femoral neck; radiolucency is more marked in individuals with osteoporosis. B, This area radiolucency simulates a pathologic fracture in patients with traumatic fracture of the femoral neck caused by rotation of the head. After reduction this appearance is no longer seen.

FIGURE 7-52, Additional example of a simulated destructive lesion after fracture of an osteoporotic femur.

FIGURE 7-53, Left, Simulated fracture of the femoral neck in a 68-year-old woman, produced by hypertrophic lipping, best seen in the lateral projection (right).

FIGURE 7-54, Two examples of skin folds simulating fractures of the femur.

FIGURE 7-55, Prominent vertical striation of the bone of the femoral neck in a normal 12-year-old girl.

The Trochanters

FIGURE 7-56, Normal irregularity of the ossification centers of the greater and lesser trochanters in a 3-year-old girl.

FIGURE 7-57, Normal irregularity of the trochanteric apophyseal line in a 7-year-old boy

FIGURE 7-58, Accessory ossification center of the greater trochanter in a 16-year-old girl. A, Plain film. B, CT scan.

The Shaft of the Femur

FIGURE 7-59, Normal osteosclerosis of the premature. This sclerosis is caused by the proportionally thicker cortical bone and incomplete development of the medullary cavities. This appearance reverts to normal in the first weeks of life.

FIGURE 7-60, Physiologic “periostitis” of the newborn. This finding is not seen before the age of 1 month, is symmetric in distribution although not necessarily concentric, and may be seen in only one view.

FIGURE 7-61, Additional examples of physiologic “periostitis” of the newborn, seen in two 4-month-old infants. Incorporation, evident here, is essentially completed by 6 months of age.

FIGURE 7-62, Physiologic anterior bowing of the femurs in a heavy 19-month-old girl. This is a self-limited phenomenon that disappears as the child matures.

FIGURE 7-63, Combined anterior and lateral physiologic bowing of the tibias in a 12-month-old girl.

FIGURE 7-64, Bilateral localized changes in the femurs of a 78-year-old man that are thought to represent the origin of the vastus lateralis muscles.

FIGURE 7-65, Origin of the vastus lateral muscle on plain film (A) and on T1-weighted sagittal (B) and axial (C) MR images.

FIGURE 7-66, Speckled trabeculation of the intertrochanteric area, which should not be mistaken for cartilaginous tumor matrix or bone infarction. These are reinforced trabeculae seen in osteoporotic bone.

FIGURE 7-67, Development of the speckled pattern of the femur in a young woman immobilized after a stroke. A, Baseline. B, Four years later, the bone has become osteopenic from disuse, and speckles have appeared.

FIGURE 7-68, Very lucent femoral metaphyses in osteoporosis.

FIGURE 7-69, Multiple transverse lines in the femoral shaft in a healthy 35-year-old man. These were present bilaterally. The same phenomenon can be seen in the humerus.

FIGURE 7-70, The femoral linea aspera–pilaster complex for the insertion of the adductor and extensor muscles.

FIGURE 7-71, Left, The pilaster complex misdiagnosed as a fracture of the femur (←). Right, CT scan shows the cortical ridge (←) but no fracture.

FIGURE 7-72, A through D, The same entity as shown in Figure 7.71 , seen bilaterally. Note the simulated periostitis in the lateral projections ( B and D ).

FIGURE 7-73, A through D, Bilateral linear intramedullary densities of the femurs in a 22-year-old woman.

FIGURE 7-74, A through D, Bilateral linear intramedullary densities of the femurs in a 67-year-old woman. Seen more commonly in elderly women without known disease, such densities are apparently of no clinical significance.

FIGURE 7-75, Unusual endocortical scalloping in a 70-year-old woman with no known disease, presumably representing a reflection of osteoporosis.

FIGURE 7-76, Normal nutrient vascular channels of the femora.

FIGURE 7-77, Nutrient foramen in a 7-year-old boy that, when added to the normal cortical thickening of the posterior aspect of the femur, was mistaken for an osteoid osteoma. Left, Frontal projection. Center, Lateral projection. Right, CT scan.

FIGURE 7-78, The nutrient channel of the femur.

FIGURE 7-79, Three examples of lucent fissures in the posterior cortex of the femur that might be mistaken for fracture lines.

FIGURE 7-80, Typical juvenile benign cortical defects. These lesions are very common in the distal femur and are of no clinical significance.

FIGURE 7-81, Additional examples of juvenile benign cortical defects. A, Multiloculate. B, Multiple lesions with thick sclerotic margins. C, Healing.

FIGURE 7-82, Healing juvenile benign cortical defect in a 17-year-old boy (←). Note the mixed lucency and sclerosis. Note also the longitudinal striations in the metaphysis, a common finding in young people ( ).

FIGURE 7-83, Huge healed juvenile benign cortical defect in an 18-year-old woman.

FIGURE 7-84, Very dense healed juvenile benign cortical defect in a 24-year-old woman.

FIGURE 7-85, Prominent longitudinal striations of the bone in a normal 13-year-old girl.

The Distal End of the Femur

FIGURE 7-86, “Tug” lesion of the medial aspect of the distal femur in an adolescent, representing bone formation in the insertion of the adductor magnus muscle.

FIGURE 7-87, Additional example of the “tug” lesion of the femur in an adult (←). Note also calcification in the medial collateral ligament ( ) and an ossicle below of the same etiology ( ).

FIGURE 7-88, Very large “tug” lesion of the medial femoral metaphysis resembling an osteochondroma.

FIGURE 7-89, Bilateral cortical thickenings related to insertion of the vastus lateralis muscle, a common radiologic finding, in a young man.

FIGURE 7-90, Prominent insertion of the medial head of the gastrocnemius. A, Plain film. B, T2-weighted MR image.

FIGURE 7-91, Normal triangular area of radiolucency seen in the metaphysis of the distal femur in an osteoporotic individual (←). The density in the midportion is related to the linea aspera ( ).

FIGURE 7-92, Triangular radiolucency in an 11-year-old girl.

FIGURE 7-93, Normal lucencies in the distal femur mistaken for metastases in a patient with breast carcinoma. The lateral projections were normal.

FIGURE 7-94, Nutrient foramen of the distal femur.

FIGURE 7-95, Examples of transverse (“growth”) lines of the distal femoral metaphyses. Although frequently associated with disease states, these lines are often seen in patients without contributory history.

FIGURE 7-96, Detailed view of transverse lines of the distal femur in a younger child.

FIGURE 7-97, Two examples of normal metaphyseal radiolucencies, an accompanying feature of osteosclerosis of the newborn (see Fig. 7.59 ). The new bone formed at the metaphysis is often more radiolucent, producing an appearance that might be mistaken for evidence of systemic disease. This finding is often the product of intrauterine stress.

FIGURE 7-98, Dense zones of provisional calcification are often mistaken for the lines of heavy metal poisoning. These zones vary considerably in thickness in healthy children and in the same child at different ages. They tend to be proportionately thicker during the second to fifth years.

FIGURE 7-99, Additional examples of normal zones of provisional calcification. A, A 14-month-old child. B, A 2-year-old child.

FIGURE 7-100, Two examples of normal irregularity in ossification of the posterior aspect of the distal femur in 2-year-old children.

FIGURE 7-101, A, The posterior irregularity of the posterior aspect of the distal femur in a 2-year-old child. B, Note the radiolucency in the medial aspect of the femoral metaphysis, which is probably the product of the posterior cortical irregularity.

FIGURE 7-102, Four examples of the metaphyseal radiolucencies illustrated in the previous figure, seen here in 5- and 6-year-old children.

FIGURE 7-103, Irregularity of the anterior aspect of the femoral metaphysis in a 3-year-old boy.

FIGURE 7-104, Three examples of irregularity of the cortex of the anterior aspect of the femur, immediately above the epiphyseal line. This entity is seen in adolescence and is a transient event. A, An 11-year-old boy. B, A 13-year-old boy. C, A 15-year-old boy.

FIGURE 7-105, A, B, Irregular defect in the cortex of the medial posterior aspect of the distal femur is a common finding between ages 12 and 16 years. This is a fibrous lesion, which often demonstrates fine perpendicular spiculation of bone (B) and may be mistaken for a malignant bone tumor. It appears to be developmental in origin and disappears with advancing age. The lesion seems to be similar in nature to other metaphyseal irregularities seen elsewhere in the body at the same age. It is important to note that the metaphyseal irregularities in the medial posterior aspects of the distal end of the femur are “cold” on nuclear scanning, suggesting that they are not avulsive in nature.

FIGURE 7-106, Good detail of the architecture of the medial femoral cortical irregularity in a 15-year-old boy.

FIGURE 7-107, Medial femoral cortical irregularity in a 13-year-old boy with a large spur at the inferior margin of the lesion (←).

FIGURE 7-108, Distal femoral cortical irregularities on both sides in a 10-year-old boy.

FIGURE 7-109, Residua of the irregularity of the cortex in the area of the medial femoral defects described in Figures 7-107 and 7-108 . A, A 17-year-old boy. B, A 23-year-old man. C, A 35-year-old man.

FIGURE 7-110, A, Typical benign cortical defect of the femur in a 12-year-old boy. B, Follow-up film made 3 years later shows the typical medial cortical irregularity. This evolution lends weight to the concept of the similar nature of these two entities.

FIGURE 7-111, The medial distal femoral cortical irregularity in a 13-year-old boy. Note the spiculations of bone (←) and the absence of cortex. The nuclear scan appearance was normal.

FIGURE 7-112, Coexistence of the medial posterior cortical defect (←) and a benign cortical defect ( ).

FIGURE 7-113, Irregularity of the posterior aspect of the distal femur is a common finding in adolescents that is often mistaken for the new bone formation of a neoplasm. This lesion is apparently related to the medial cortical irregularity illustrated in Figure 7.105 and is of no clinical significance. It is “cold” on nuclear scanning, suggesting that it is not an avulsive injury and is more likely to be a reflection of growth.

FIGURE 7-114, The posterior femoral cortical irregularities on CT scan.

FIGURE 7-115, A through E, The posterior cortical irregularity of the femur in a 7-year-old child. A, B, Radiographs. C, T1-weighted sagittal MR image. D, T1-weighted axial MR image. E, Short tau inversion recovery (STIR) axial MR image.

FIGURE 7-116, The posterior cortical irregularity of the femur in a 12-year-old boy. A, B, Plain films. C, T1-weighted MR image shows area of low signal intensity in that portion of the medullary cavity. D, T2-weighted MR image shows increased signal intensity at that site.

FIGURE 7-117, A through D, Huge symmetric bilateral posterior cortical irregularities in a 10-year-old girl.

FIGURE 7-118, Large irregular posterior femoral defect in a 12-year-old girl that was proven by biopsy to be fibrous in nature.

FIGURE 7-119, Residua of the posterior femoral defect in a 30-year-old man.

FIGURE 7-120, A, B, A more exaggerated residuum of the posterior femoral defect in a 33-year-old man.

FIGURE 7-121, Developmental excavation on the posterior aspect of the medial femoral condyle.

FIGURE 7-122, Four examples of cortical irregularities in the posterior cortex of the distal femur that have persisted into adult life, presumably the end products of the process shown in Figures 7-113 and 7-118 . These defects are important only because they might be mistaken for significant lesions.

FIGURE 7-123, Simulated lesions of the anterior aspect of the distal femur produced by rotation at the time of filming.

FIGURE 7-124, Physiologic bowing and knock-knee. A, Physiologic bowing in a 1½2-year-old girl. B, Physiologic knock-knee in a 3½2-year-old girl. In normal development, there is a varoid phase to age 2 years and a valgoid phase between 2 and 12 years. These are normal physiologic events that correct spontaneously.

FIGURE 7-125, Physiologic bowing. Note the slight beaking of the medial tibial plateaus, the medial wedging of the ossification centers of the knees, and the thickening of the medial cortices of the tibias. These are all reflections of this physiologic state.

FIGURE 7-126, Physiologic knock-knees in a 3-year-old boy. Note lack of any architectural derangement.

FIGURE 7-127, Evolution of physiologic bowing. A, An 18-month-old child. B, A 2-year-old child showing spontaneous correction. C, A 4-year-old child. This appearance is normal.

FIGURE 7-128, A, A 1-year-old girl with physiologic bowing. Note the “fragmentation” of the medial aspect of the tibial metaphysis (←). B, Same patient at age 2 years. Note resolution of the physiologic bowing.

FIGURE 7-129, Asymmetric development of the distal femoral epiphysis in a 7-year-old boy with no symptoms referable to the knee joints.

FIGURE 7-130, Cleft distal femoral epiphysis seen only in the lateral projection. Any epiphysis or apophysis may develop from multiple centers.

FIGURE 7-131, Normal irregularity of ossification of the medial femoral metaphyses in young children.

FIGURE 7-132, Normal irregularities of ossification in the knees of young infants.

FIGURE 7-133, Additional examples of normal irregularities of the distal femoral epiphyses in 1-year-old children.

FIGURE 7-134, Normal irregular ossification of the lateral aspect of the distal femoral epiphysis in a 9-year-old child.

FIGURE 7-135, A, Normal developmental lucency of the lateral aspects of the distal femoral epiphysis simulating a destructive lesion in a 6-year-old boy. B, Similar but less marked changes are present in the opposite limb. C, Similar changes in a 12-year-old boy.

FIGURE 7-136, Normal developmental lucencies in the epiphyses and metaphyses of the distal femur in a 10-year-old boy.

FIGURE 7-137, Developmental radiolucent stripes in the medial aspect of the distal femoral epiphysis simulating a fracture. A, A 5-year-old boy. B, A 7-year-old boy.

FIGURE 7-138, An excellent example of the normal irregularity of the distal femoral epiphyses in an 8-year-old. This appearance explains the misleading shadows seen in the frontal projections of the knees of children of this age.

FIGURE 7-139, A through C, Normal irregularity of the lateral femoral condyles in a 7-year-old boy. These irregularities are posteriorly located and are seen in the tunnel views of both knees ( B and C ) but not in the conventional AP projection (A).

FIGURE 7-140, Medial and lateral femoral condylar irregularities seen in the tunnel views of both knees of a 10-year-old boy. These irregularities are often mistaken for evidence of osteochondritis.

FIGURE 7-141, Simulated osteochondritis dissecans in a 6-year-old boy.

FIGURE 7-142, Simulated osteochondritis dissecans in an 11-year-old boy. Note that the irregularities are not seen in the frontal projection (left), are well demonstrated in the tunnel projection (middle), and are seen posteriorly in the lateral projection (right).

FIGURE 7-143, Normal irregularity in ossification of the medial femoral condyle in a 12-year-old boy that was mistaken for osteochondritis dissecans. A, Plain film. B, C, Coronal and sagittal gradient echo, T2*-weighted MR images show typical ossification variant.

FIGURE 7-144, Normal irregularity in ossification of the medial femoral condyle in a 10-year-old girl simulating osteochondritis dissecans on radiograph (A) and on T1-weighted (B) and gradient echo, T2-weighted (C) MR images.

FIGURE 7-145, Normal irregularities in ossification of the lateral femoral condyle in an 8-year-old boy. A, Frontal projection. B, Oblique projection. C, Lateral projection.

FIGURE 7-146, Ossification variant of the medial femoral condyle of the left knee in a 12-year-old boy. A, AP film. B, Oblique view. C, Oblique projection. D, CT scan shows no evidence of osteochondritis dissecans.

FIGURE 7-147, Spurlike configuration of the medial femoral epiphysis in a 12-year-old girl, which should not be mistaken for an epiphyseal osteochondroma.

FIGURE 7-148, The terminal sulcus of the lateral condyle seen in the lateral projection (A) may reflect itself in the frontal plane (B) in a manner that suggests an abnormality.

FIGURE 7-149, Two additional examples of normal contour irregularities of the condyles seen in lateral projection. This contour alteration may be seen in the patellar view as well (see Fig. 7.150 ).

FIGURE 7-150, Normal contour alteration of the medial condyle seen in tangential projection.

FIGURE 7-151, The lateral femoral condyle may normally appear flattened. This appearance should not be mistaken for evidence of an impaction fracture.

FIGURE 7-152, A, Flattening of the lateral femoral condyle may be associated with discoid lateral meniscus, as documented by a gradient echo, T2*-weighted coronal MR image (B).

FIGURE 7-153, Osseous excrescences along the surfaces of the distal femur seen in tunnel view are not to be confused with hypertrophic lipping.

FIGURE 7-154, The grooves of the articular surface of the medial condyle of the femur represent a normal variant that should not be confused with osteochondritis or a fracture.

FIGURE 7-155, The groove for the popliteus tendon should not be mistaken for a pathologic process.

FIGURE 7-156, The grooves of the popliteus tendon seen in the tunnel view.

FIGURE 7-157, An ossicle in the popliteus groove. (Cyamella sesamoid in the popliteus tendon.)

FIGURE 7-158, A large cyamella with overgrowth of the superior margin of the popliteus groove.

FIGURE 7-159, Bipartite cyamella.

FIGURE 7-160, Variations in development of the fabella. A, Double fabella. B, Bifid fabella. C, Irregular fabella.

FIGURE 7-161, Tripartite fabella. It should be noted that the fabella and cyamella may not be present bilaterally.

FIGURE 7-162, Meniscal ossicle of the medial meniscus. A, AP projection. B, Lateral projection. C, T1-weighted sagittal MR image. D, Coronal short tau inversion recovery (STIR) MR image.

FIGURE 7-163, Normal areas of sclerosis of the intercondylar fossae in a 25-year-old man.

FIGURE 7-164, The transverse intermeniscal ligament. A, Radiograph. B, T1-weighted MR image.

FIGURE 7-165, Calcification in the posterior cruciate ligament in a patient being examined for an acute injury.

FIGURE 7-166, Normal radiolucent anterior segment of the distal femoral epiphysis in a 12-year-old boy resulting from the fact that less bone is traversed anteriorly than posteriorly.

FIGURE 7-167, Normal radiolucency simulating a cystic lesion.

FIGURE 7-168, Triangular area of radiolucency that may be confused with the defect of osteochondritis dissecans.

FIGURE 7-169, Stippled appearance of distal femur caused by the closing epiphyseal plate in a 13-year-old boy. This appearance should not be confused with chondroid matrix of a neoplasm.

FIGURE 7-170, Two examples of the foramina for the nutrient vessels of the distal end of the femur.

FIGURE 7-171, Normal radiolucency of the femoral notch originally diagnosed as a metastatic deposit.

FIGURE 7-172, Fat pad between joint capsule and quadriceps tendon that may be mistaken for a lipohemarthrosis.

FIGURE 7-173, A, B, Bilateral ossification in Hoffa's fat pad.

FIGURE 7-174, The “vacuum” phenomenon in the knee joint.

FIGURE 7-175, Simulated narrowing of the medial compartments of the knees in a 14-year-old girl. This misleading appearance is the result of the double contour of the medial tibial plateau. Measurements should be made from the articular surface of the distal femoral condyle to the most distal of the tibial articular margins (←). Measured in this fashion, the widths of the two compartments are equal.

FIGURE 7-176, A, B, Simulated medial compartment narrowing on standing film for the same reason as that shown in Figure 7.175 . This problem can also be resolved with a tunnel projection (C), which demonstrates equality of measurement of the two compartments.

FIGURE 7-177, Some normal individuals show true asymmetry in the height of the medial and lateral compartments. Left, A 48-year-old man. Standing films show asymptomatic symmetric narrowing of the medial compartments. Right, Films of the same person 10 years later show no change in compartment height.

THE PATELLA

FIGURE 7-178, Normal irregularity of the growing patellae in a 7-year-old boy.

FIGURE 7-179, Unusual dense stippling of the patellae in a 2-year-old girl, best seen in the frontal projection. Note that the other epiphyses are normal.

FIGURE 7-180, Normal variation in development of the patella in an 8-year-old boy simulating a fracture.

FIGURE 7-181, Normal irregularity and clefts in the patella of a 6-year-old boy.

FIGURE 7-182, Normal developmental irregularities of the patellae, seen in the tangential projection. A, A 7-year-old child. B, A 15-year-old child.

FIGURE 7-183, Three examples of accessory ossification centers at the superior pole of the patella.

FIGURE 7-184, A, B, Irregular patellar ossification misdiagnosed as a fracture. C, Simulated fracture lines in the normal patella of a 7-year-old boy. D, Normal irregularity of the superior aspect of the patella in a 12-year-old boy simulating osteochondritis or a fracture.

FIGURE 7-185, Variations in development of the patella in that might be mistaken for fracture. A, A 6-year-old child. B, An 8-year-old child.

FIGURE 7-186, Apparent fracture of the superior aspect of the patella in a 14-year-old boy as a result of a secondary ossification center at the superior pole.

FIGURE 7-187, Unfused accessory ossification center at the upper pole of the patella in an 80-year-old man.

FIGURE 7-188, A, B, Normal asymmetric development of accessory ossification centers in a 9-year-old child. Note apparent fragmentation of the lower pole of the patella in B.

FIGURE 7-189, Long secondary apophysis of the anterior and inferior aspects of the patella in an 11-year-old boy.

FIGURE 7-190, Nonunion of the anterior patellar apophysis illustrated in Figure 7.189 .

FIGURE 7-191, Three examples of accessory ossification centers simulating fractures. A, A 7-year-old boy. B, An 8-year-old boy. C, A 12-year-old boy.

FIGURE 7-192, Variable patterns of ossification of the inferior pole of the patella.

FIGURE 7-193, Examples of accessory center of ossification at the lower pole of the patella that may be mistaken for a fracture.

FIGURE 7-194, A, The closing accessory center at the inferior pole of the patella was suspected of being a fracture. B, A comparison view made of the opposite knee shows an even more misleading appearance.

FIGURE 7-195, A, Fusing accessory centers of ossification at the inferior pole of the patella. B, Fusion is now complete. Patellae with large accessory centers of this type often tend to attain the elongated configuration illustrated in B. They may be associated with patella alta.

FIGURE 7-196, Unfused accessory ossification center at the inferior pole of the patella in a 19-year-old man, showing its closure over a 3-month period.

FIGURE 7-197, Developmental clefts in the patella of a 17-year-old boy.

FIGURE 7-198, Patellar clefts.

FIGURE 7-199, Accessory ossicle at the medial aspect of the patella.

FIGURE 7-200, Unusual spurlike configuration of the medial aspect of the patella in a 20-year-old man.

FIGURE 7-201, Early bipartite patella in a 10-year-old girl.

FIGURE 7-202, Bipartite patella, which may easily be mistaken for a fracture. Note the well-defined space between the major elements.

FIGURE 7-203, An additional example of a bipartite patella, which is well demonstrated in the tangential projection. The rounded contour of the patellar elements seen in this projection is useful in the differentiation from fracture.

FIGURE 7-204, A, Segmented patellae with two pieces on patients right and three on the left. B, C, Segmented patella with four pieces.

FIGURE 7-205, A, Unilateral bipartite patella. Note that the smaller elements in bipartite patellae often do not accurately correspond in size with the adjacent fossa. B, Unilateral bipartite patella (←), but with corresponding fossa on opposite side ( ). C, D, Bipartite patella on the medial side. The majority of bipartite patellae are located on the lateral side. E, F, Tripartite patella.

FIGURE 7-206, Tripartite patella. Note the rounded contours in the tangential projection.

FIGURE 7-207, Three examples of forme fruste bipartite patella.

FIGURE 7-208, A, The smaller element of a bipartite patella is usually smaller than the fossa in the major portion. B, Occasionally, however, it is larger than the fossa.

FIGURE 7-209, An unusual variety of partitioned patella. A, Radiograph. B, Tomogram.

FIGURE 7-210, Horizontal bifid patella, a rare type of segmentation.

FIGURE 7-211, A, B, Patellar “teeth” caused by spurring of the tendon interdigitations.

FIGURE 7-212, A, B show the dorsal patellar defect. These cortical lucencies are of no clinical significance and should not be confused with osteochondritis dissecans of the patella. C, Film obtained 1 year later; note the sclerosis of healing. D, In film obtained 2 years later, resolution is complete.

FIGURE 7-213, The dorsal patellar defect on plain film (A) and gradient echo, T2*-weighted axial MR image (B).

FIGURE 7-214, Dorsal patellar defects in a 12-year-old girl.

FIGURE 7-215, Bilateral areas of increased sclerosis in the posterior surfaces of the patellae in a 20-year-old woman.

FIGURE 7-216, Variation in ossification of the articular surface of the patella and the adjacent femoral physis.

FIGURE 7-217, Simulated fracture of the upper pole of the patella produced by a small flangelike projection, best seen in the lateral projection.

FIGURE 7-218, A through C, Example of simulated stress fracture of the patella from same cause as described in Figure 7.217 . Note that no discontinuity is seen in the lateral projection (B) or in the tomogram (C).

FIGURE 7-219, Unusual configurations of the lower poles of the patellae. A, B, A 12-year-old. C, A 14-year-old girl.

FIGURE 7-220, Unusual configurations of the patella resulting from enthesopathy.

FIGURE 7-221, Two examples of ossicles or sesamoid bones in the patellar tendon.

FIGURE 7-222, A, B, Bilateral striking appearance of the fossa in the articular surface of the patella.

FIGURE 7-223, The normal fossa in the articular surface of the patella. A, Left knee. B, Right knee. C, T1-weighted MR image of right knee showing the fossa. (←) D, Fat-saturated T2-weighted MR image of right knee showing normal overlying cartilage.

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