Mr Imaging Findings of Lesions Involving Cartilage and Bone in the Paediatric Knee: a Pictorial Review

jans-_Opmaak 1 21/10/11 10:25 Pagina 247

JBR–BTR, 2011, 94: 247-253.

MR IMAGING FINDINGS OF LESIONS INVOLVING CARTILAGE AND BONE IN THE PAEDIATRIC KNEE: A PICTORIAL REVIEW

L.B.O. Jans, J.L. Jaremko, M. Ditchfield, K.L. Verstraete

The knee is the joint which is most commonly imaged by MRI in children and adolescents. With increasing participation in competitive sports, traumatic knee injuries with osteochondral lesions are increasingly common in children. However, it is also important to exclude non traumatic conditions that result in defects of the articular cartilage and/or subchondral bone plate or growth plate of the knee, since timely diagnosis and therapy may help prevent lifelong disability in these patients. Moreover, there are normal variants that occur in the ossifying knee that should not be mistaken for lesions. The aim of this essay is to review the wide range of conditions that may result in MRI signal changes of the ossifying knee in children.

Musculoskeletal injury in children is common and can lead to lifelong disability. The knee joint is often involved in sports-related as well as in non traumatic pathological conditions in the paediatric population. Magnetic resonance imaging (MRI) is the imaging investigation of choice due to the absence of radia- tion, multiplanar imaging options, high image resolution and superb soft tissue contrast. MRI visualizes the cartilaginous ends of growing bones, bone marrow and supporting soft tissue structures making it ideally suited for evaluation of bone and cartilage injury and the complicating AB growth disturbance in young patients (1). Fig. 1. — Chondral fracture in an 11-year-old boy. Although several of the injuries in A. Coronal T1-weighted image demonstrates a large loose body (arrows) with signal the paediatric knee occur in adults as intensity f cartilage in the femorotibial joint space. B. Sagittal T1-weighted image demonstrates the avulsed osteochondral fragment well, the paediatric knee is also (arrows) anteriorly in the femorotibial joint space. Note the presence of hydrops subject to unique developmental (asterisk). and pathological processes which may be related to the presence of unfused physes (2). Musculoskeletal lesions can be the first manifestation patients. These lesions are often sub- cartilaginous fragment in the joint of systemic disease. Also, there are tle but can be significant clinically space may be demonstrated (Fig. 1a- normal findings of the growing and and may easily remain undetected. It b). developing femoral condyle such as is important to include MRI 1.2. Physeal Fractures ossification variants that are not sequences that are sensitive to artic- seen in the adult population and ular cartilage injury in the evaluation Approximately 15% of all paediatric should be differentiated from pathol- of internal derangement of the pae- fractures involve the physis (6). MRI ogy (3). diatric knee (4). demonstrates the cartilaginous path The aim of this pictorial review is 1.1.1. Chondropathy of the fracture, as well as associated to familiarize the reader with the MR MRI shows chondropathy as focal findings (7). Nearly 15% of all phy- imaging features of the wide variety cartilaginous thickening, superficial seal fractures lead to growth arrest of lesions that may result in damage or deep ulceration or fissuring and with the formation of a bone bridge to the cartilage and bone in the demonstrates associated bone across the physis, causing subse- paediatric knee. bruise and osteochondral separated quent limb shortening or angular fractures (5). deformity. The distal femur (1.4%) 1. Traumatic paediatric knee lesions and proximal tibia (0.8%) are infre- 1.1.2. Chondral fracture quent sites of physeal fracture, but 1.1. Chondral injury With shear stress mechanism of have high incidences of post-trau- Cartilaginous injuries are the injury, chondral avulsion fracture matic premature physeal fusion most common lesions after acute may occur. A focal defect in the artic- (35% and 16% respectively) (1). knee trauma in skeletally immature ular cartilage and the presence of a 1.3. Temporary Patellar Dislocation (TPD)/Patellar subluxation From: Ghent University Hospital, Ghent, Belgium. TPD is often an unexpected find- Address for correspondence: L.B.O. Jans, M.D., Ghent University Hospital, De ing on MRI of the knee in children. Pintelaan 185, B-9000 Ghent, Belgium. E-mail: [email protected] Paediatric manifestations of TPD jans-_Opmaak 1 21/10/11 10:25 Pagina 248

248 JBR–BTR, 2011, 94 (5)

trauma with stretched ACL may result in avulsion of the tibial spine. The composition of the tibial spine in children renders it weaker than the ACL (11). Non-operative versus surgical management is determined by the degree of displacement of the osseous fragment and is controver- sial in skeletally immature athletes because the reconstruction tech- nique requires crossing of the growth plate (5). 1.6. Osteochondritis dissecans (OCD) AB Repetitive microtrauma is felt to play a role in the etiology of juvenile Fig. 2. — Temporary patellar dislocation (patellar subluxation) in a 7-year-old girl. OCD. The lesion is thought to be an Axial T2-weighted image with fat saturation demonstrates bone marrow edema osteochondral fracture with avascu- (arrows) in (A) the lateral femoral condyle and (B) in the entire patella. lar necrosis of subchondral bone and overlying cartilage (Fig. 5). In the knee, OCD most commonly affects the lateral aspect of the medial femoral condyle (3). MRI confirms the diagnosis and evaluates the stability of the lesion (12). A high T2 signal intensity rim surrounding a juvenile OCD lesion indicates instability if it has the same signal intensity as adjacent joint fluid, if it is surrounded by a second outer rim of low T2 signal intensity, or if it is accompanied by multiple breaks in the subchondral bone plate on T2- weighted images. Cysts surrounding the lesion indicate instability only if they are multiple or large in size (> 5 mm) (13, 14). AB MRI can assess the integrity of the overlying cartilage and identifies the Fig. 3. — Patellar sleeve avulsion in a 10-year-old boy. presence of loose bodies in the A. Sagittal and (B) coronal T2-weighted images with fat saturation demonstrate a joint (15). OCD must be differentiat- hypointense fracture line with surrounding bone marrow oedema (arrows) in the ed from normal variants of ossifica- inferior aspect of the patella. tion in the paediatric knee, most commonly seen at the posterior aspect of the lateral femoral condyle seen on MRI are similar to those in be present if the avulsion is com- without associated bone marrow plete. In some cases the avulsed adults. Bone bruising of the infero- oedema (16, 17). medial patella and the lateral fragment may be entirely cartilaginous and therefore occult on radio - femoral condyle (kissing contusions), 2. Non-traumatic paediatric knee graphy. MRI establishes the extent of cartilage injuries of the inferomedial lesions patella and the lateral femoral the cartilaginous injury and delin- condyle, osteochondral fragments eates joint involvement and the 2.1. Infection degree of fragment displacement. and injuries of the medial patellar Infection of the musculoskeletal This information can be useful diag- restraints are the most common find- system in children is challenging. In nostically and in guiding therapy. ings of TPD on MRI (Fig. 2a-b) (2, 8). the appropriate clinical context, the Treatment involves prompt surgical 1.4. Patellar sleeve avulsion main responsability for the radiolo- reduction and internal fixation of the gist is to raise the possibility of infec- disrupted patellar tendon. If a bony The composition of the ossifying tion when reporting conventional fragment is visible on conventional patella renders it weaker than the radiography or ultrasound studies radiography and the displacement is patellar tendon. Rapid forceful con- and to select the appropriate next less than 2 mm, closed treatment in traction of the quadriceps against imaging modality to confirm diagno- a cast in extension is justified (10). resistance in partial flexion of the sis. Since no single MRI feature can Injuries at the superior patellar- knee can result in avulsion fracture differentiate septic from non septic quadriceps junction also occur but of the inferior patellar pole. The arthritis, biopsy may be warranted in are less frequent (9). typical patient is 9 to 12 years old the work-up of these lesions (18-20). and presents with acute inferior 1.5. Tibial spine avulsion fracture patellar pain. The cartilaginous injury 2.1.1. Septic arthritis is always much more extensive than Tibial spine avulsion fractures are A missed diagnosis of septic the avulsed fragment of ossified common before physeal closure arthritis of the knee in children may bone (Fig. 3a-b) (9). Patella alta may (Fig. 4a-b). In paediatric athletes, lead to severe long-lasting sequelae jans-_Opmaak 1 21/10/11 10:25 Pagina 249

MRI OF THE PAEDIATRIC KNEE — JANS et al 249

Fig. 4. — Tibial spine avulsion in a 14-year-old boy. Fig. 5. — Osteochondritis dissecans in A. Coronal T1-weighted image and (B) sagittal T2-weighted image with fat saturation an 11-year-old boy. demonstrate avulsion fracture of the tibial spine (long arrows) with bone marrow oede- Sagittal Pd-weighted image demon- ma of the fracture fragments. There is no tear of the anterior cruciate ligament (short strates a large osteochondral lesion (long arrows). arrows) surrounded by a rim of high signal (short arrows) and multiple small perilesional cysts (arrowhead) in keeping with unstable OCD. Note the lesion extends along the middle and posterior third of the femoral condyle.

first choice imaging modality for complementary examination if there is a clinical suspicion but conventional radiography is negative. MRI can also be guided by other imaging studies (eg. Tc bone scan in case of suspected chronic recurrent osteo - A B myelitis). In osteomyelitis, the tubular bones are most of the time affected Fig. 6. — Bone and cartilage lesions due to septic arthritis of the knee in (a) an 9-year-old boy and (b) in a 7-year-old girl. at the metaphysis level, but epiphy- A. Coronal T1-weighted image demonstrates ill-defined osteochondral defects seal involvement may occur as well (arrows) in the medial and lateral femoral epiphysis. (19). In early osteomyelitis bone mar- B. Coronal T1-weighted image demonstrates a large bony bar of the distal epiphysis row oedema is present, enhancing of the femur (arrow) following meningococcus septic arthritis of the knee. with IV Gadolinium administration. There is usually a poor delineation between normal and abnormal bone and disability. In young patients with probability of infection (20). Bone marrow. In chronic osteomyelitis, an acutely swollen knee joint, the erosions appear earlier compared there is a sharp differentiation diagnosis of septic arthritis must with non septic arthritis. Con - between normal and abnormal soft always be excluded. If sepsis is comitant bone erosions and marrow tissues surrounding the bones. suspected, urgent joint aspiration is oedema are highly suggestive of Gadolinium enhancement delineates mandatory since early appropriate septic arthritis, and the added pres- intraosseous and soft tissues treatment is curative (18). Numerous ence of synovial oedema and thick- abscesses and collections. Infection investigations including plain radio - ening, soft tissue oedema or bone extending to the growth plates is graphs, US, CT and MRI may be marrow enhancement is even more ideally demonstrated in the coronal needed for diagnosis and to guide suggestive of infection (Fig. 6a-b) or sagittal imaging planes. therapy. It is important to realize that (21). Joint effusion can be present in Underlying preexisting conditions changes on conventional radio - both septic and non septic joints, up include sickle cell disease, immuno - graphy are only seen in late stage to one third of patients with septic deficient state and chickenpox (19). disease, therefore negative radio - arthritis lacks a joint effusion. CRMO (Chronic recurrent multifocal graphs do not exclude septic Abnormal marrow signal is worri- osteomyelitis) is considered part of arthritis. US, CT or MR guided some for concomitant osteo myelitis, the SAPHO syndrome (synovitis, percutaneous biopsy may obtain the especially if diffuse and visible on T1- acne, pustulosis, hyperostosis, causative micro-organism (19). weighted images (22). osteitis). In CRMO, multiple foci of Although no single MRI feature can osteocondensation and osteolysis 2.1.2. Osteomyelitis differentiate septic from non septic with ill-defined bone marrow edema arthritis, the presence of several MRI is not suitable for screening involving metaphysis and diaphyses abnormal findings increases the in paediatric osteomyelitis, but it are seen (19). jans-_Opmaak 1 21/10/11 10:25 Pagina 250

250 JBR–BTR, 2011, 94 (5)

condition (24). Moreover, MRI may play a role in therapy monitoring. The early MRI features of JIA in the knee joint are irregularity of the infrapatellar fat pad, lymphadenopa- thy, ill-defined areas of bone marrow oedema and joint effusion. If these features are present gadolinium can be administered to assess the degree of synovial hypertrophy. Erosions are one of the endpoints of the disease process in JIA and indicate destruction of both bone and cartilage (Fig. 7a-b). Erosions can occur at any point along the articular surface of the bone but are ABmost often seen at the insertion site of the intraosseous ligaments and at Fig. 7. — Juvenile arthritis of the knee in a 9-year-old girl. the sites of synovial reflection, as A. Coronal T1-weighted image demonstrates a subchondral lesion (arrows) in the these areas have relatively less medial femoral epiphysis. overlying protective cartilage (25). B. Sagittal T1-weighted image demonstrates a subchondral lesion (arrow) in the Erosions are seen as well circum- weight-bearing aspect of the medial femoral epiphysis. Note the presence of a large scribed lesions with low T1 and high joint effusion (asterisk). T2 signal, often showing marked enhancement following gadolinium administration (26). Differential diagnosis with septic arthritis is often challenging and biopsy may be necessary (20). 2.2.2. PVNS (Pigmented villonodular synovitis) PVNS is a mono-articular process involving the knee in 80% (27). With PVNS, synovial proliferation and signal loss due to chronic hemosiderin deposition is demonstrated. The latter finding is accentuated on gradient echo imaging due to magnetic susceptibility artefact, known as ‘blooming’. Contrast-enhanced imaging is useful in diagnosis and ABassessment of the lesion extent of PVNS in paediatric patients (28). MRI Fig. 8. — Haemophiliac arthropathy of the knee in a 13-year-old boy. features are particularly useful for A. Sagittal T2-weighted image with fat saturation demonstrates several ill-defined differentiating PVNS from hemophil- subchondral lesions and a subchondral cyst (arrowheads) in the lateral femoral ia. Differential diagnosis includes epiphysis and lateral tibial epiphysis. Hemosiderin staining is demonstrated as a T2 hypointens lining of the synovium (arrow). Moderate to large joint effusion is present hemophilia (typical clinical history) (asterisk). and hemangioma (presence of B. Sagittal T1-weighted image with fat saturation after IV contrast administration serpentine vascular channels) (27). demonstrates ill-defined subchondral lesions (short arrows) in the medial and lateral 2.2.3. Haemophilia femoral epiphysis. The synovium enhances and is slightly thickened (long arrows). Haemophiliac arthropathy due to recurrent haemartrosis is the main clinical feature of severe haemophil- 2.2. Inflammatory disease chronic uveitis, arthritis of the temporomandibular joint or cervical ia and a major cause of morbidity in A variety of conditions may result spine ankylosis. Anemic symptoms this group of patients. The most in cartilagenous or bony lesions of in patients with hemophilia also common findings in haemophiliac the knee due to synovial inflamma- suggest the correct diagnosis (3). arthropathy of the knee are joint tion, including juvenile idiopathic effusion, synovial hypertrophy, syn- arthritis (JIA), haemophilia, pigment- 2.2.1. JIA ovial haemosiderin deposits and ed villonodular synovitis (PVNS) and Juvenile idiopathic arthritis (JIA) osteochondral lesions resulting in intraarticular vascular lesions. is the most common chronic rheu- joint space narrowing (Fig. 8a-b). The Clinical presentation may be sugges- matic disease of childhood and is an latter finding is accentuated on tive. Patients with JIA classically important cause of short-term and gradient echo imaging. MRI clearly present with persisting articular long-term disability (23). The radiolo- depicts these changes, which may inflammatory symptoms > 6 weeks, gist has an important role in sug- not be identified by conventional with onset before the age of 16- gesting the diagnosis of JIA as the radiography in early stages, even years-old and may present with clinician may not be aware of the before the presence of symptoms. jans-_Opmaak 1 21/10/11 10:25 Pagina 251

MRI OF THE PAEDIATRIC KNEE — JANS et al 251

A B

Fig. 9. — Juxtaarticular VM (venous malformation) of the knee in a 17-year-old girl. A. Axial T2-weighted image with fat saturation demonstrates a small VM (arrow) cen- tred along the anterior aspect of the knee joint, extending into the synovium. B. Coronal T2-weighted image with fat saturation demonstrates signal changes of the lateral femoral condyle and tibial plateau representing subchondral cyst formation (arrows) and focal bone marrow oedema (arrows). An osteophyte of the lateral femoral Fig. 10. — Osteonecrosis in a 10-year- condyle is present (thin arrow). old boy. Sagittal T2-weighted image with fat saturation demonstrates well circumscribed lesions with an interface that appears as a thin, winding line in the epiphysis (arrows) and metaphysis (arrowheads) of the femur and tibia.

strong association of these deep lesions with arthropathy (nearly 90%), often with haemosiderin deposition indicating bleeding into the joint (Fig. 9a-b). The frequency of arthropathy increases with increasing extension of the VM into the joint. MRI evaluation of all juxtaarticular VMs identifies possible associated arthropathy, which may A B be important in determining the timing and aggressiveness of Fig. 11. — Bone tumour of the knee (a) a 15 year-old boy and (b) a 10-year-old boy. therapy (32). A. Sagittal T1-weighted images demonstrates a large osteosarcoma in the distal 2.2.4.2. Synovial haemangioma femoral diaphysis, metafysis and epiphysis with cortical breach and extraosseous invasion (arrows). Synovial haemangioma presents B. Sagittal T1-weighted images demonstrates a large tumour (arrows) in the as a nodular mass lesion. Ultra - proximal tibial epiphysis with cortical breach and intraarticular invasion. Diagnosis of sound demonstrates arterial flow enchondroma was confirmed after lesion biopsy. within the lesion. Within the mass, signal void due to the presence of abnormal vessels may mimic hemosiderin deposits. Intense enhance- Early diagnosis of joint haemorrhage 2.2.4.1. Venous malformation (VM) ment of the mass lesion following and synovial hypertrophy alters the VM is the most common vascular gadolinium administration with flow therapeutic management and may malformation of the extremities and voids suggests the diagnosis (33). prevent progressive joint destruc- is clinically blue and compressible. 2.3. Osteonecrosis tion and surgery (29, 30, 31). Ultrasound demonstrates venous 2.2.4. Vascular lesions flow within the lesion. Typical MR Osteonecrosis of the knee is a imaging findings of VM include cys- frequent complication of high dose Vascular lesions with intraarticular tic or sinusoidal T2 hyperintense steroid treatment of acute leukaemia extension may cause osteochondral structures, presence of phleboliths in children and can lead to joint lesions due to inflammatory and central enhancement pat- collapse and may predispose to response of the synovium and tern (32). secondary arthritis (34). synovial fluid to hemosiderin There is a high prevalence (nearly MRI findings of osteonecrosis deposition. The presence of abnor- 50%) of intra-articular extension of might be present before any symp- mal juxtasynovial vascular struc- venous malformations (VMs) toms occur, allowing the earliest and tures will suggest the diagnosis (32). adjacent to the knee joint, and a most accurate diagnosis of osteo - jans-_Opmaak 1 21/10/11 10:25 Pagina 252

252 JBR–BTR, 2011, 94 (5)

and biopsy of the tumour is mandatory. Correlation with age and site of the lesion (eg. epiphyseal, diaphy- seal or metaphyseal) may be helpful in the differential diagnosis. Metastasis of neuroblastoma and leukemia have to be included in the differential diagnosis in infants whereas osteosarcoma is the most common malignant primary bone tumour in children and adolescents (36-37). The most important role of MRI is to image the extend of the primary tumour and to look for skip metasta- ABsis. Dynamic contrast-enhanced MRI may be helpful in monitoring Fig. 12. — Bipartite patella in a 14-year-old girl. response to therapy in osteosarco- A. Coronal T2-weighted image with fat saturation demonstrates bipartite configura- ma since the active tumoral tissues tion of the cranial lateral aspect of the patella (arrows). in size with treatment, whereas B. Sagittal Pd-weighted image with fat saturation demonstrates a hypointense lesion lesional volume reduction does indi- in the cranial aspect of the patella (arrows). The retropatellar articular cartilage appears cate response to therapy for Ewing normal (long arrow). sarcoma (37).

3. Developmental ossification variants 3.1. Bipartite patella (BP) and dorsal patellar defect (DPD) The patella usually arises from a single ossifying nucleus, but secondary centres of ossification may be located in the supero-lateral quadrant. These usually fuse to form a single bone, but may remain separate to form a bipartite or multipartite patella (Fig. 12a-b). The dorsal patellar defect is also thought to represent a failure in the ossification of the patella (38-40). AB Skeletal normal variants may become symptomatic after repetitive Fig. 13. — Normal ossification variants of the femoral condyle mimicking osteochon- stress: painful bipartite patella is dral lesion. related to the effects of traction A. Sagittal T1-weighted MR image in a 7-year-old girl demonstrates an ill-defined forces in the fibrocartilaginous syn- osseous defect (arrow) in the posterior third of the lateral femoral condyle. An chondrosis (37). Most DPD remain ossification completely fills the defect. asypmtomatic as the cortical defect B. Sagittal T1-weighted MR image in a 10-year-old boy of the knee demonstrates the is usually compensated by over- presence of extra ossification centres (arrows) in the non-ossified cartilage of the posterior third of the lateral femoral condyle. growing articular cartilage (40). 3.2. Ossification variants of the femoral condyle necrosis (35). The lesions typically 2.4. Tumour Normal variants of ossification have a geographical appearance are common in rapidly growing chil- with a characteristic interface The diagnosis of a bone tumour in dren and should not be confused between living and dead bone at the children is often delayed and at time with lesions (16, 17). Ossification periphery of the lesion that appears of diagnosis intraarticular extension defects in the posterior femoral as a thin, winding line with low T1 with osteochondral destruction may condyles with intact overlying carti- signal and high T2 signal that be present. Enhancing osseous lage, accessory ossification centres, circumscribes and clearly demar- mass lesions with extensive sur- spiculation, greater residual physeal cates the zone of necrosis (Fig. 10a- rounding bone marrow oedema, cartilage and lack of bone marrow b). In case of progression with sub - breach of the cortex with periosteal oedema are features of developmen- chondral collapse, which is a compli- reaction and extension into the soft tal variants (17). Sample images of cation of progressive osteonecrosis tissues fit every definition of malig- ossification variant are presented in near a joint surface, the inner zone of nant tumour (Fig. 11a). However, Fig. 13 a-b. Early ossification centre necrosis may show low signal benign bone tumours may demon- in the residual cartilage is the most intensity or might be inhomoge- strate extraosseous extension as common ossification variant, fol- neous (36). well (Fig. 11b). Prompt recognition lowed by spiculated configuration of jans-_Opmaak 1 21/10/11 10:25 Pagina 253

MRI OF THE PAEDIATRIC KNEE — JANS et al 253

the secondary ossification centre, injury versus tibial spine fracture in 26. Malattia C., Damasio M.B., pre-ossification centre, extra ossifi- the skeletally immature knee: a com- Magnaguagno F., et al.: Magnetic res- cation centre, puzzle piece and parison of skeletal maturation and onance imaging, ultrasonography, incomplete puzzle piece configura- notch width index. J Pediatr Orthop, and conventional radiography in the tion ossification variant (17). 2004, 24: 185-188. assessment of bone erosions in juve- 12. Bohndorf K.: Osteochondritis (osteo- nile idiopathic arthritis. Arthritis chondrosis) dissecans: A review and Rheum, 2008, 59: 1764-1772. Conclusion new MRI classification. Eur Radiol, 27. Murphey M.D., Rhee J.D., Lewis R.B., 1998, 8: 103-112. et al.: Pigmented villonodular synovi- Lesions of the knee become 13. De Smet A.A., Fisher D.R., Graf B.K., tis: Radiologic-Pathologic correlation. increasingly more common in et al.: Osteochondritis dissecans of Radiographics, 2008, 28: 1493-1518. the knee: value of MR imaging in 28. Eckhardt B.P., Hernandez R.J.: children. MRI clearly depicts osteo- determining lesion stability and the Pigmented villonodular synovitis: MR chondral lesions of the paediatric presence of articular cartilage imaging in pediatric patients. Pediatr knee and can differentiate traumatic defects. AJR, 1990, 155: 549-553. Radiol, 2004, 34: 943-947. from non traumatic knee lesions. 14. Kijowski R., Blankenbaker D.G., 29. Dobon M., Lucia J., Aguilar C., Recognition of these conditions is Shinki K., et al.: Juvenile versus adult Mayayo E., Roca M., Solano V., mandatory since timely diagnosis osteochondritis dissecans of the Pena S., Giralt M., Ferrandez A.: Value guides therapy and may prevent life- knee: appropriate MR imaging crite- of magnetic resonance imaging for long disabilties. Normal ossification ria for instability. Radiology, 2008, the diagnosis and follow-up of variants may occur in the ossifying 248: 571-578. haemophilic arthropathy. 15.Hughes J.A., Cook J.V., Haemophilia, 2003, 9: 76-85. knee and can mimic lesions. Churchill M.A., et al.: Juvenile osteo- 30. Nuss R., Kilcoyne R., Rivard G., et al..: chondritis dissecans: a 5-year review Late clinical, plain x-ray and magnetic of the natural history using clinical resonance imaging findings in References and MRI evaluation. Pediatr Radiol, haemophilic joints treated with radio - 2003, 33: 410-417. synoviorthesis. Haemophilia, 2000, 6: 1. Ecklund K.: Magnetic resonance 16. Nawata K., Teshima R., Morio Y., et al.: 658-663. imaging of pediatric musculoskeletal Anomalies of ossification in the 31. Ng W.H., Chu W.C., Shing M.K., et al.: trauma. Topics in Magnetic posterolateral femoral condyle: Role of imaging in management in Resonance Imaging, 2002, 13: 203- assessment by MRI. Pediatr Radiol, hemophilic patients. Am J Roent - 218. 1999, 29: 781-784. genol, 2005, 184: 1619-23. 2. Dupuis C.S., Westra S.J., Makris J., 17. Gebarski K., Hernandez R.J.: Stage-I 32. Jans L., Ditchfield M., Jaremko J.L., Wallace E.C.: Injuries and conditions osteochondritis dissecans versus Stephens N., Verstraete K.: MRI of the extensor mechanism of the normal variants of ossification in the demonstrates the extension of juxta- pediatric knee. Radiographics, 2009, knee in children. Pediatr Radiol, 2005, articular venous malformation of 29: 877-886. 35: 880-886. the knee and correlates with joint 3. Strouse P.J.: MRI of the knee: key 18. Johnson K., Witkop D., Haigh F., changes. Eur Radiol, 2010, 7: 1792-8. points in the pediatric population. Ryder C., Gardner-Medwin J.M.: The 33. Helpert C., Davies A.M., Evans N., Pediatr Radiol, 2010, 40: 447-452. early magnetic resonance imaging Grimer R.J.: Differential diagnosis of 4. Oeppen R.S., Connolly S.A., features of the knee in juvenile idio- tumour-like lesions of the infrapatel- Bencardino J.T., Jaramillo D.: Acute pathic arthritis. Clinical Radiology, lar (Hoffa's) fat pad: pictorial review injury of the articular cartilage and 2002, 57: 466-471. with an emphasis on MR imaging. subchondral bone: a common but 19. Schmit P., Glorion C.: Osteomyelitis in Eur Radiol, 2004, 14: 2337-2346. unrecognized lesion in the immature infants and children. Eur Radiol, 2004, 34. Karimova E.J., Kaste S.C.: MR knee. AJR, 2004, 182: 111-117. 14: 44-54. imaging of osteonecrosis of the knee 5. Raissaki M., Apostolaki E., 20. Bancroft L.W.: MR imaging of infec- in children with acute lymphocytic Karantanas A.H.: Imaging of sports tious processes of the knee. Radiol leukemia. Pediatr Radiol, 2007, 37: injuries in children and adolescents. Clin N Am, 2007, 45: 931-941. 1140-1146. European Journal of Radiology, 2007, 21. Graif M., Schweitzer M.E., Deely D., 35. Karimova E.J., Rai S.N., Ingle D., et 1: 86-96. Matteucci T.: The septic versus non- al.: MRI of knee osteonecrosis in chil- 6. Mizuta T., Benson W.M., Foster B.K., et septic inflamed joint: MRI characteris- dren with leukemia and lymphoma: al.: Statistical analysis of the inci- tics. Skeletal Radiol, 1999, 28: 616- part 2, clinical and imaging patterns. dence of physeal injuries. J Pediatr 20. AJR, 2006, 186: 477-482. Orthop, 1987, 7: 518-523. 22. Karchevsky M., Schweitzer M.E., 36. Dorfman H.D., Czerniak B.: Bone 7. Jaramillo D., Kammen B., Shapiro F.: Morrison W.B., Parellada J.A.: MRI cancers. Cancer, 1995, 75: 203-210. Cartilaginous path of physeal frac- findings of septic arthritis and associ- 37. Hoffer F.: Primary Skeletal neoplasms: tureseparations: Evaluation with MR ated osteomyelitis in adults. AJR, Osteosarcoma and Ewing sarcoma. imaging – An experimental study 2004, 182: 119-122. Topics in Magnetic Resonance with histologic correlation in rabbits. 23. Damasio M.B., Malattia C., Martini A., Imaging, 2002, 13: 231-240. Radiology, 2000, 215: 504-511. Toma P.: Synovial and inflammatory 38. Mellado J.M., Salvado E., Ramos A., 8. Zaidi A., Babyn P., Astori I., White L., diseases in childhood: role of new Camins A., Sauri A.: Dorsal defect on Doria A., Cole W.: MRI of traumatic imaging modalities in the assess- a multipartite patella: imaging find- patellar dislocation in children. ment of patients with juvenile idio- ings. Eur Radiol, 2001, 11: 1136- Pediatr Radiol, 2006, 36: 1163- pathic arthritis. Pediatr Radiol, 2010, 1139. 1170. 40: 985-998. 39. Lawson J.P.: Clinically significant radi- 9. Connolly S.A., Connolly L.P., 24. Johnson K.: Imaging of juvenile idio- ologic anatomic variants of the skele- Jaramillo D.: Imaging of sports pathic arthritis. Pediatr Radiol, 2006, ton. AJR, 1994, 163: 249-255. injuries in children and adolescents. 36: 743-758. 40. Van Holsbeeck M., Vandamme B., Radiol Clin N Am, 2001, 39: 773-789. 25. Kight A.C., Dardzinski B.J., Laor T., et Marchal G., Martens M., Victor J., 10. Hunt D.M., Somashekar N.: A review al.: Magnetic resonance evaluation of Baert A.L.: Dorsal defect of the patel- of sleeve fractures of the patella in the effects of juvenile rheumatoid la: concept of its origin and relation- children. Knee, 2005, 12: 3-7. arthritis on distal femoral weight- ship with bipartite and multipartite 11. Kocher M.S., Mandiga R., Klingele K., bearing cartilage. Arthritis Rheum, patella. Skeletal Radiol, 1987, 16: 304- et al.: Anterior cruciate ligament 2004, 50: 901-905. 311.