summary Congenital Popliteal Webbing, also known as popliteal pterygium syndrome, is an inherited condition that affects the face, limbs, and genitalia. Diagnosis is made clinically by the presence of a characteristic web running behind the knee from ischial tuberosity down to the heel. MRI studies are helpful for operative planning to identify location of neurovascular structures. Treatment is generally surgical resection in the majority of cases. Epidemiology Incidence rare affects 1:300,000 Demographics affects males and females equally Etiology Genetics inheritance pattern autosomal dominant can also be sporadic associated with advanced paternal age mutations results from a mutation in the IRF6 gene encodes a transcription factor that is active in cells that give rise to tissues in the head and face also involved in the development of the skin and genitalia Associated conditions cleft lip/palate syndactyly criptorchidism bifid scrotum hypoplasia of the labia majora congnitive delays spina bifida Anatomy Popliteal pterygium subcutaneous fibrous band lies superficially along the free edge of the pterygium sciatic/peroneal nerve lies deep to the fibrous band, usually halfway between the free edge and the apex popliteal artery/vein usually lies deep in the popliteal space Presentation Physical exam extensive web running behind the knee from ischial tuberosity down to the heel usually bilateral limits lower extremity extension, abduction, and rotation syndactyly triangular folds of skin over the nails of the large toes tissue connecting the upper and lower eyelids (ankyloblepharon) or jaws (syngnathia) abnormal genitalia hypoplastic labia majora in females cryptorchidism or bifid scrotum in males cleft lip/palate Imaging Radiographs recommended views AP lateral findings knee flexion contracture MRI indications operative planning used to assess location of neurovascular structures given wide variation and risk for injury Treatment Nonoperative observation indications rare Operative surgical resection indications most cases Techniques Surgical resection technique resection or tenotomy of fibrous band z-plasty of overlying skin can perform sciatic nerve grafting or tendon lengthening if needed