An upper leg prosthesis adapter for connecting to an upper leg shaft, having - a knee joint (2a, 2b) that can be pivoted between a standing position and a swinging position with a proximal knee joint upper part (4a, 4b) and a distal knee joint lower part (5a, 5b) which are connected via a ventral joint arm and a dorsal joint arm (20a, 20b), wherein - the ventral joint arm is connected in an articulated manner to the proximal knee joint upper part (4a, 4b) via a ventral, upper knee joint axis and in an articulated manner via a ventral, lower knee joint axis to the distal knee joint lower part (5a, 5b), and the dorsal joint arm (20a, 20b) is connected in an articulated manner to the proximal knee joint upper part (4a, 4b) via a dorsal, upper knee joint axis and in an articulated manner to the distal knee joint lower part (5a, 5b) via a dorsal, lower knee joint axis, and - a foot joint (3a, 3b) for pivotably connecting a foot part (10a, 10b) to a lower leg unit connected to the knee joint (2a, 2b) wherein - the lower leg unit has a ventral connection element and a dorsal connection element designed to transmit pushing and pulling forces, characterized in that - the ventral connection element is rotably hinged on one end to the foot part (10a, 10b) via a ventral foot joint axis and on the other end to the distal knee joint lower part (5a, 5b), and the dorsal connection element is connected on one end to the foot part (10a, 10b) via a dorsal foot joint axis and on the other end in an articulated manner to the proximal knee joint upper part (4a, 4b) and the dorsal joint arm (20a, 20b) via the dorsal, upper knee joint axis such that shifting the knee joint (2a, 2b) from the standing position to the swinging position causes a dorsal extension of the foot part (10a, 10b). - a knee joint (2a, 2b) that can be pivoted between a standing position and a swinging position with a proximal knee joint upper part (4a, 4b) and a distal knee joint lower part (5a, 5b) which are connected via a ventral joint arm and a dorsal joint arm (20a, 20b), wherein - the ventral joint arm is connected in an articulated manner to the proximal knee joint upper part (4a, 4b) via a ventral, upper knee joint axis and in an articulated manner via a ventral, lower knee joint axis to the distal knee joint lower part (5a, 5b), and the dorsal joint arm (20a, 20b) is connected in an articulated manner to the proximal knee joint upper part (4a, 4b) via a dorsal, upper knee joint axis and in an articulated manner to the distal knee joint lower part (5a, 5b) via a dorsal, lower knee joint axis, and - the ventral joint arm is connected in an articulated manner to the proximal knee joint upper part (4a, 4b) via a ventral, upper knee joint axis and in an articulated manner via a ventral, lower knee joint axis to the distal knee joint lower part (5a, 5b), and the dorsal joint arm (20a, 20b) is connected in an articulated manner to the proximal knee joint upper part (4a, 4b) via a dorsal, upper knee joint axis and in an articulated manner to the distal knee joint lower part (5a, 5b) via a dorsal, lower knee joint axis, and - a foot joint (3a, 3b) for pivotably connecting a foot part (10a, 10b) to a lower leg unit connected to the knee joint (2a, 2b) - the lower leg unit has a ventral connection element and a dorsal connection element designed to transmit pushing and pulling forces, characterized in that - the ventral connection element is rotably hinged on one end to the foot part (10a, 10b) via a ventral foot joint axis and on the other end to the distal knee joint lower part (5a, 5b), and the dorsal connection element is connected on one end to the foot part (10a, 10b) via a dorsal foot joint axis and on the other end in an articulated manner to the proximal knee joint upper part (4a, 4b) and the dorsal joint arm (20a, 20b) via the dorsal, upper knee joint axis such that shifting the knee joint (2a, 2b) from the standing position to the swinging position causes a dorsal extension of the foot part (10a, 10b). - the ventral connection element is rotably hinged on one end to the foot part (10a, 10b) via a ventral foot joint axis and on the other end to the distal knee joint lower part (5a, 5b), and the dorsal connection element is connected on one end to the foot part (10a, 10b) via a dorsal foot joint axis and on the other end in an articulated manner to the proximal knee joint upper part (4a, 4b) and the dorsal joint arm (20a, 20b) via the dorsal, upper knee joint axis such that shifting the knee joint (2a, 2b) from the standing position to the swinging position causes a dorsal extension of the foot part (10a, 10b).