Diagnostic imaging of the knee in children with arthrogryposis and knee extension or hyperextension contracture.

PURPOSE: Amyoplasia (type 1), characterized by quadrimelic limb involvement, is one of the most common types of arthrogryposis. In children with hyperextension or extension contracture of the knee, subluxation or dislocation of the knee joint with an associated subluxation or dislocation of the patella is frequently seen. Patellar malpositioning may be secondary to congenital hypoplasia of the patellar groove of the femur and/or dysplasia of the patellofemoral joint. A contracted quadriceps tendon and illiotibial band, as seen in extension contractures of the knee in arthrogryposis, may also contribute to patella alta and lateral subluxation of the patella. The aim of our study is to determine the position of the patella in children with quadrimelic arthrogryposis and knee extension contracture.

METHODS: The inclusion criteria for this study were as follows: patients diagnosed with arthrogryposis multiplex congenita group 1, a knee extension contracture present from birth, follow-up from birth or early childhood, at least yearly physical examinations, and a knee ultrasonography or magnetic resonance imaging study performed. Patellar position was determined, and the cartilaginous femoral sulcus angle, as well as the osseous femoral sulcus angle, was measured.

RESULTS: Clinically, none of patella in any of the patients could be palpated before surgery. The patella was displaced superiorly and laterally in 16/16 knees as seen on ultrasonography. Magnetic resonance imaging also showed the patella to be displaced superior and laterally.

CONCLUSIONS: All patients in our series with extension contracture of the knee and type 1 arthrogryposis had a patella that was superior and lateral to the patellar groove. We found that quadricepsplasty and relocation of the patella improved knee flexion. All patients regained active knee extension in 6 months postsurgery.

LEVEL OF EVIDENCE: Level III-diagnostic.