TBX4 and coxopodopatellar syndrome: Patellar dysplasia is one risk factor causing patellar dislocation and subsequent osteoarthritis development.[1, 2, 3, 4] It has been reported as a feature in many genetic disorders such as small patella syndrome and nail patella syndrome, and studies on these disorders have implicated that several genes were involved in patellar dysplasia.[5, 6] Bongers et al.[7] found that TBX4 was associated with small patella syndrome, the disease that is characterized mainly by patellar reduction or absence in six families through genetic association analysis and sequencing.