A balloon catheter device (10, 10a, 10b, 10c) comprising: an elongate catheter shaft (14, 12a, 12b); an inflatable balloon (18, 18a, 18b) having and outer surface wherein the inflatable balloon is positioned on the catheter shaft (14, 12a, 12b); and at least one cutting or scoring element (22, 22a, 22b, 22c) that is moveable between a first position wherein it does not cause the balloon (18, 18a, 18b) to perform a cutting or scoring function and a second position wherein it does cause the balloon (18, 18a, 18b) to perform a cutting or scoring function; wherein said at least one cutting or scoring element (22, 22a, 22b, 22c) comprises a single elongate member that forms loops or convolutions around the balloon (18, 18a, 18b) when in the second position, wherein: when the cutting or scoring element (22, 22a, 22b, 22c) is in the second position, the cutting or scoring element (22, 22a, 22b, 22c) does extend over at least a portion of the outer surface of the balloon (18, 18a, 18b) in a manner that will cause the cutting or scoring element (22, 22a, 22b, 22c) to perform a cutting or scoring function upon inflation of the balloon (18, 18a, 18b); characterised in that: when the cutting or scoring element (22,22a,22b,22c) is in the first position, the cutting or scoring element (22,22a,22b,22c) does not extend over the surface of the balloon (18,18a,18b) in a manner that would cause the cutting or scoring element (22,22a,22b,22c) to perform a cutting or scoring function upon inflation of the balloon (18,18a,18b). an elongate catheter shaft (14, 12a, 12b); an inflatable balloon (18, 18a, 18b) having and outer surface wherein the inflatable balloon is positioned on the catheter shaft (14, 12a, 12b); and at least one cutting or scoring element (22, 22a, 22b, 22c) that is moveable between a first position wherein it does not cause the balloon (18, 18a, 18b) to perform a cutting or scoring function and a second position wherein it does cause the balloon (18, 18a, 18b) to perform a cutting or scoring function; wherein said at least one cutting or scoring element (22, 22a, 22b, 22c) comprises a single elongate member that forms loops or convolutions around the balloon (18, 18a, 18b) when in the second position, wherein: when the cutting or scoring element (22, 22a, 22b, 22c) is in the second position, the cutting or scoring element (22, 22a, 22b, 22c) does extend over at least a portion of the outer surface of the balloon (18, 18a, 18b) in a manner that will cause the cutting or scoring element (22, 22a, 22b, 22c) to perform a cutting or scoring function upon inflation of the balloon (18, 18a, 18b); characterised in that: when the cutting or scoring element (22,22a,22b,22c) is in the first position, the cutting or scoring element (22,22a,22b,22c) does not extend over the surface of the balloon (18,18a,18b) in a manner that would cause the cutting or scoring element (22,22a,22b,22c) to perform a cutting or scoring function upon inflation of the balloon (18,18a,18b). when the cutting or scoring element (22, 22a, 22b, 22c) is in the second position, the cutting or scoring element (22, 22a, 22b, 22c) does extend over at least a portion of the outer surface of the balloon (18, 18a, 18b) in a manner that will cause the cutting or scoring element (22, 22a, 22b, 22c) to perform a cutting or scoring function upon inflation of the balloon (18, 18a, 18b); characterised in that: when the cutting or scoring element (22,22a,22b,22c) is in the first position, the cutting or scoring element (22,22a,22b,22c) does not extend over the surface of the balloon (18,18a,18b) in a manner that would cause the cutting or scoring element (22,22a,22b,22c) to perform a cutting or scoring function upon inflation of the balloon (18,18a,18b).