A length adjustment device for a finger motion rail of a therapeutic device for carrying out a continuous, passive and/or actively assisted movement of a finger and/or a thumb of a hand, comprising: - at least one adjustment rail; - at least one holding means, movable with respect to the adjustment rail, for holding the finger motion rail; - at least one first blocking mechanism, arranged on the holding means, for blocking the movement of the holding means in a first direction along the adjustment rail; - at least one second blocking mechanism, arranged on the holding means, for blocking the movement of the holding means in a second direction along the adjustment rail; - at least one carriage, - wherein the carriage can be operatively connected to the finger motion rail via at least one connecting element (20a; 20b); - wherein the carriage is configured to be moved along the adjustment rail by means of a drive for moving the finger motion rail; - wherein the carriage is designed such that, when it is moved by means of the drive in the first direction along the adjustment rail and contacts the first blocking mechanism, it exerts a force on the first blocking mechanism, such that the first blocking mechanism is released, and the holding means together with the finger motion rail is movable in the first direction by movement of the carriage, and - wherein the carriage is designed such that, when it is moved by means of the drive in the second direction along the adjustment rail and contacts the second blocking mechanism, it exerts a force on the second blocking mechanism, such that the second blocking mechanism is released, and the holding means together with the finger motion rail is movable in the second direction by movement of the carriage. - at least one adjustment rail; - at least one holding means, movable with respect to the adjustment rail, for holding the finger motion rail; - at least one first blocking mechanism, arranged on the holding means, for blocking the movement of the holding means in a first direction along the adjustment rail; - at least one second blocking mechanism, arranged on the holding means, for blocking the movement of the holding means in a second direction along the adjustment rail; - at least one carriage, - wherein the carriage can be operatively connected to the finger motion rail via at least one connecting element (20a; 20b); - wherein the carriage is configured to be moved along the adjustment rail by means of a drive for moving the finger motion rail; - wherein the carriage can be operatively connected to the finger motion rail via at least one connecting element (20a; 20b); - wherein the carriage is configured to be moved along the adjustment rail by means of a drive for moving the finger motion rail; - wherein the carriage is designed such that, when it is moved by means of the drive in the first direction along the adjustment rail and contacts the first blocking mechanism, it exerts a force on the first blocking mechanism, such that the first blocking mechanism is released, and the holding means together with the finger motion rail is movable in the first direction by movement of the carriage, and - wherein the carriage is designed such that, when it is moved by means of the drive in the second direction along the adjustment rail and contacts the second blocking mechanism, it exerts a force on the second blocking mechanism, such that the second blocking mechanism is released, and the holding means together with the finger motion rail is movable in the second direction by movement of the carriage.