The ‘Small-Patella’ Syndrome

Abstract

We describe a syndrome combining abnormalities of the pelvis, knee and foot in three related patients with a familial history of small dislocated patellae. The clinical and radiological appearance of the patella and pelvis is consistent with the 'small-patella' syndrome, a rare autosomal dominant disorder. There were also previously unreported deformities affecting the feet. The 'small-patella' syndrome, first described by Scott and Taor in 1979, is characterised by patellar aplasia or hypoplasia and abnormalities of the pelvic girdle. We describe a family in which the classic anomalies of this syndrome are associated with minor morphological variations of the hindfoot. We present the radiological features and discuss the aetiology. CASE REPORTSCase 1 (III3, Fig. 1). A 68-year-old woman was admitted with bilateral chronic knee and ankle pain. She was obese and had a personal and family history of recurrent dislocation of small patellae (Fig. 1).Physical examination revealed small, laterally placed patellae, flat feet, and limited subtalar motion. The other peripheral joints were normal and there was no nail dystrophy or leg shortening. Radiographs (Fig. 2) showed multiple skeletal abnormalities, including small dislocated patellae, bilateral defective formation of the ischiopubic junction, hypoplasia of the lesser trochanters, infra-acetabular notches, ball-and-socket ankle joints, secondary radiological signs of bilateral talocalcaneal coalition with narrowing of the posterior talocalcaneal joint space and a talar beak, hypertrophy of the neck of the talus and broadbased plantar calcaneal exostoses.Three-dimensional CT of the pelvis showed thin ischiopubic junctions and emphasised the infra-acetabular notches (Fig. 3a). Coronal CT of the right hindfoot (Fig. 3b) identified talocalcaneal coalition at the level of the sustentaculum tali. No other skeletal abnormalities were seen. Case 2 (IV1, Fig. 1). This 49-year-old woman, the daughter of the patient in case 1, had small patellae. Radiographs of the pelvis, knees and hindfeet showed small patellae, hypoplasia of the ischiopubic junction, hypertrophy of the neck Fig. 1 Genealogical table of the family reported.

Magnetic Resonance Image Findings in A Rare Case of Bilateral Knee Pain in A Small Patella Syndrome Patient

“…It is characterized by total absent or hypoplastic patella and abnormalities seen at the pelvic bone and feet 1,2,4-6 . Scott-Taor revealed 12 members from a family with either absent of small patella were seen to have abnormalities at the pelvic girdle and proximal femur 9 . This skeletal dysplasia disorder resulted from mutations in the TBX4 gene that causes impairment in the early and later stages of the limb development leading to the skeletal deformities 2 .…”

“…A plain knee radiograph would reveal absent or small patella. Other abnormalities that possibly can be observed are subluxated or dislocated patella, small medial femoral condyle and lateral tibial plateu, dysplastic fibular head, flattening of the femoral intercondylar notch and trochlear dysplasia [4][5][6]8,9 . From a foot radiographs pathognomonic findings that are suggestive of SPS include widened first web space, short fourth and fifth metatarsal bones and pes planus 1,[4][5][6]8,9 .…”

“…Other abnormalities that possibly can be observed are subluxated or dislocated patella, small medial femoral condyle and lateral tibial plateu, dysplastic fibular head, flattening of the femoral intercondylar notch and trochlear dysplasia [4][5][6]8,9 . From a foot radiographs pathognomonic findings that are suggestive of SPS include widened first web space, short fourth and fifth metatarsal bones and pes planus 1,[4][5][6]8,9 . Dellestable F et al described several findings that were found in a foot radiograph in minority of the cases that comprise of talocalcaneal coalition, ball and socket ankle joint, hypertrophy of neck of talus and calcaneal exostoses 10 .…”

Congenital aplasia of the patella and the distal third of the quadriceps mechanism

“…Congenital absence of the patella is a very rare anomaly that may occur either in isolation or as part of a more generalized malformation syndrome [1][2][3][4][5]. The absent patella itself seldom causes significant disability [1] unless there is an associated deformity of the knee or malalignment of the quadriceps mechanism that may require treatment.…”