A prosthetic elbow comprising: a fixed member structure configured to connect to one of a forearm portion and an upper arm portion; and a powered gearbox mechanism for rotating the forearm portion to varying angular positions about an elbow axis (x-x), in which the prosthetic elbow further comprises a housing structure configured to connect to the other of the forearm portion and the upper arm portion, the housing structure is rotatable relative to the fixed member structure about an axis of rotation of the forearm portion ; and the powered gearbox mechanism is disposed within and supported by the housing structure , the powered gearbox mechanism comprising: a motor connected to the housing structure and having a motor shaft , a planetary frictional drive connected to the motor shaft and the housing structure , and a strain wave gear set having an input driven by the planetary frictional drive and an output attached to the fixed member structure , wherein the powered gearbox mechanism is configured to convert an output of the motor into a rotation of the housing structure relative to the fixed member structure , thereby causing the rotation of the forearm portion to varying angular positions relative to the upper arm, in which the planetary frictional drive includes a sun element connected to the motor shaft , a ring element fixed to the housing structure , and a set of planet elements for driving the input of the strain wave gear set , characterised in that the powered gearbox mechanism further comprises a brake mechanism , wherein an input of the brake mechanism is coupled to and driven by the set of planet elements of the planetary frictional drive , and an output of the brake mechanism is coupled to and drives the input of the strain wave gear set . a fixed member structure configured to connect to one of a forearm portion and an upper arm portion; and a powered gearbox mechanism for rotating the forearm portion to varying angular positions about an elbow axis (x-x), in which the prosthetic elbow further comprises a housing structure configured to connect to the other of the forearm portion and the upper arm portion, the housing structure is rotatable relative to the fixed member structure about an axis of rotation of the forearm portion ; and the powered gearbox mechanism is disposed within and supported by the housing structure , the powered gearbox mechanism comprising: a motor connected to the housing structure and having a motor shaft , a planetary frictional drive connected to the motor shaft and the housing structure , and a strain wave gear set having an input driven by the planetary frictional drive and an output attached to the fixed member structure , a motor connected to the housing structure and having a motor shaft , a planetary frictional drive connected to the motor shaft and the housing structure , and a strain wave gear set having an input driven by the planetary frictional drive and an output attached to the fixed member structure , wherein the powered gearbox mechanism is configured to convert an output of the motor into a rotation of the housing structure relative to the fixed member structure , thereby causing the rotation of the forearm portion to varying angular positions relative to the upper arm, in which the planetary frictional drive includes a sun element connected to the motor shaft , a ring element fixed to the housing structure , and a set of planet elements for driving the input of the strain wave gear set , characterised in that the powered gearbox mechanism further comprises a brake mechanism , wherein an input of the brake mechanism is coupled to and driven by the set of planet elements of the planetary frictional drive , and an output of the brake mechanism is coupled to and drives the input of the strain wave gear set . <EOS>