Ehlers-Danlos syndromes (EDS) form a heterogeneous group of hereditary connective tissue diseases characterized by joint hyperlaxity, cutaneous hyperelasticity and tissue fragility.

Avascular necrosis of the proximal epiphysis of the femur occurring in growing children and caused by an interruption of the blood supply to the head of the femur close to the hip joint. The necrosis is characteristically associated with flattening of the femoral head, for which reason the term coxa plana has been used to refer to this feature in the medical literature.