An apparatus for treating reflux disease of a human patient. The apparatus comprising an implantable movement restriction device, having an outer surface that includes a biocompatible material. The movement restriction device is adapted to rest against and to be kept in place contacting the stomach fundus wall, without restricting food passage in the food passageway when implanted and in function, and without injuring the stomach fundus wall in a position between the patient's diaphragm and the cardia sphincter. The movement of the cardiac notch of the patient's stomach towards the patient's diaphragm is thereby restricted, when the movement restriction device is implanted, to thereby prevent the cardia from sliding through the patient's diaphragm opening into the patient's thorax. The movement restriction device is adapted to contact directly or indirectly the diaphragm muscle to prevent such sliding of the cardia through the patient's diaphragm, so as to maintain the supporting pressure against the patient's cardia sphincter muscle exerted from the patient's abdomen. The movement restriction device having a size, when implanted and in function such that the functional movement restriction device can be completely invaginated by the stomach fundus of the human patient, and of at least 125 mm3, and a circumference of at least 15 mm.
