Joints: Widened Joint Space
Sterile hip aspiration.
Patients tend to have less painful hip symptoms than those with bacterial synovitis.
Pus or bacteria found on hip aspiration.
Other clinical parameters that increase the likelihood of bacterial infection prior to a spiration when US shows an effusion are increases in temperature, leukocyte count, and erythrocyte sedimentation rate.
Renal osteodystrophy (primary and secondary hyperparathyroidism)
Fig. 5.26, p. 512
Widened sacroiliac joints.
Mono- and polyarticular forms. Likely to have more chronic symptoms.
Pigmented villonodular synovitis (PVNS)
Fig. 5.32a–d, p. 516
Synovium is dark on T1 and T2-weighted MRI.
Masses of PVNS may appear similar to hyper-trophied synovium of JIA on MRI and US.
Symptoms change more rapidly in rheumatic fever than JIA.
Hemarthrosis (trauma, hemophilia)
Fig. 5.33a, b, p. 517
Uniform joint space narrowing. Hemosiderin in the synovium (dark on T1- and T2-weighted MRI).
Tends to affect large joints. Patients us ually a lready have a diagnosis of trauma or a b leeding disorder.
Traumatic: transient dislocation of the patella
Fig. 5.34a–c, p. 518
Lateral subluxation of the patella.
May be associated with patellofemoral dysplasia. Secondary findings of impaction fractures at the medial pole of patella and lateral femoral condyle, tears of medial retinaculum and vastus medialis.
Traumatic: radial head dislocation
Fig. 5.35, p. 518
Forearm held in pronation on tangential views of the elbow.
Caused by a sudden pull on the extended pronated forearm.
Brachial plexus palsy
Fig. 5.17, p. 505
Widened joint space in the affected shoulder. ± Flattened epiphysis proximal humerus, ± glenoid dysplasia.
Muscular hypotonia from the brachial plexus paresis causes joint instability and dysplasia as the child grows.
Developmental dysplasia of the hip
Fig. 5.20, p. 507
Pulvinar may produce widening of the hip joint and complicate adequate relocation.
Fig. 5.36a–d, p. 519
Findings depend on the phase of the disease.
Traumatic epiphyseal separation
Widening of the physis ± subluxation of the epiphysis.
Restricted to unossified epiphyses. Humerus (proximal and distal) is commonly affected.
Fig. 5.37a, b, p. 519
Joint space may be widened from erosions.
Early findings of bone marrow edema on MRI may herald later erosions.
Radial head dislocation
Long axis of the radius does not bisect the capitellum.
Progressive radial head deformity is common.
Dislocated knees, bell-shaped thorax.
Oligohydramnios due to renal agenesis leads to fetal malposition with dislocation of large joints, club feet, typical facies, and pulmonary hypoplasia.
Joint space may be widened by an osteochondroma.
Typically between the radioulnar or tibiofibular joints (proximal or distal).
Collagen vascular disorders
Joint space widening, subluxations, and dislocations.
DD: Marfan and Ehlers-Danlos syndromes.
Micromelic dysplasia with wide metaphyses, dislocations, subluxated elbows, hips, patellae.
Classic hand radiograph with subluxated thumb joints, oval phalanges, joint contractures, scoliosis.
Dislocation of large joints (knees, hips, and elbows).
Male Turner syndrome. Multisystem involvement. Anterior bowing of the sternum, genu valgum, finger anomalies, scoliosis, vertebral anomalies, Klippel-Feil syndrome.
Radial ray anomalies, hypoplastic clavicle and/or glenoid, Sprengel deformity, pectus deformities, rib anomalies.
Isolated ulnar hypoplasia or associated with other anomalies.
(see Table 5.96 )
Osteoonychodysplasia (nail–patella syndrome)
Hypoplastic or absent patella, iliac horn arising offthe central outer surface of the ilium, flared iliac wing, and small iliac angle.
Multiple epiphyseal dysplasia, Fairbank type
Small irregular epiphyses. Flattened and multicentric epiphyses at the femoral head.
Most common form of mesomelic dwarfism. Madelung deformity, shortening of both tibias.
Finger anomalies, asymmetric skeletal maturation (left vs. right), urinary system anomalies.
Cornelia de Lange syndrome
(see Table 5.50 )
Short tubular bones particularly at the forearms, cone-shaped epiphyses of the phalanges and metacarpals, premature epiphyseal fusion of hands and feet, large great toes.
Dysplasia of the radiocapitellar joint, ± radial head dislocation. Characteristic ear shape and short stature.
(see Table 5.34 )
Mesomelic dysplasia, Nievergelt type
(see Table 5.51 )
Otopalatodigital syndrome I (Taybi syndrome)
Hypoplastic clavicle, scoliosis, joint subluxations, long fingers and toes. Dense skull base, under-pneumatization of skull, short thumbs and great toes.
Trichorhinophalangeal dysplasia, types I and II
(see Table 5.33 )