A knee or ankle prosthesis, comprising: a first cylinder comprising a first cylinder port and a second cylinder port; a first piston slidable within the first cylinder; a fluid sump comprising a sump port; and a fluid circuit, comprising: a first fluid channel comprising a first channel inlet, a first channel outlet connected between a third and fourth fluid channel, and a unidirectional variable-resistance valve configured to set a variable resistance to fluid flow through the first fluid channel; a second fluid channel comprising a second channel inlet, a second channel outlet,and a second channel check valve; the third fluid channel comprising a third channel inlet, a third channel outlet, and a third channel check valve; the fourth fluid channel comprising a fourth channel inlet, a fourth channel outlet, and a fourth channel check valve; a fifth fluid channel comprising a fifth channel inlet, a fifth channel outlet, and a fifth channel check valve; a first intersection comprising the first channel inlet, the second channel outlet; and characterized in that: the first intersection further comprises the fifth channel outlet; and the fluid circuit further comprises: a second intersection comprising the first cylinder port, the second channel inlet, and the third channel outlet; a third intersection comprising the sump port, the third channel inlet, and the fourth channel inlet; and a fourth intersection comprising the second cylinder port, the fourth channel outlet, and the fifth channel inlet. a first cylinder comprising a first cylinder port and a second cylinder port; a first piston slidable within the first cylinder; a fluid sump comprising a sump port; and a fluid circuit, comprising: a first fluid channel comprising a first channel inlet, a first channel outlet connected between a third and fourth fluid channel, and a unidirectional variable-resistance valve configured to set a variable resistance to fluid flow through the first fluid channel; a second fluid channel comprising a second channel inlet, a second channel outlet,and a second channel check valve; the third fluid channel comprising a third channel inlet, a third channel outlet, and a third channel check valve; the fourth fluid channel comprising a fourth channel inlet, a fourth channel outlet, and a fourth channel check valve; a fifth fluid channel comprising a fifth channel inlet, a fifth channel outlet, and a fifth channel check valve; a first intersection comprising the first channel inlet, the second channel outlet; and characterized in that: the first intersection further comprises the fifth channel outlet; and the fluid circuit further comprises: a second intersection comprising the first cylinder port, the second channel inlet, and the third channel outlet; a third intersection comprising the sump port, the third channel inlet, and the fourth channel inlet; and a fourth intersection comprising the second cylinder port, the fourth channel outlet, and the fifth channel inlet. a first fluid channel comprising a first channel inlet, a first channel outlet connected between a third and fourth fluid channel, and a unidirectional variable-resistance valve configured to set a variable resistance to fluid flow through the first fluid channel; a second fluid channel comprising a second channel inlet, a second channel outlet,and a second channel check valve; the third fluid channel comprising a third channel inlet, a third channel outlet, and a third channel check valve; the fourth fluid channel comprising a fourth channel inlet, a fourth channel outlet, and a fourth channel check valve; a fifth fluid channel comprising a fifth channel inlet, a fifth channel outlet, and a fifth channel check valve; a first intersection comprising the first channel inlet, the second channel outlet; and characterized in that: the first intersection further comprises the fifth channel outlet; and the fluid circuit further comprises: a second intersection comprising the first cylinder port, the second channel inlet, and the third channel outlet; a third intersection comprising the sump port, the third channel inlet, and the fourth channel inlet; and a fourth intersection comprising the second cylinder port, the fourth channel outlet, and the fifth channel inlet. a second intersection comprising the first cylinder port, the second channel inlet, and the third channel outlet; a third intersection comprising the sump port, the third channel inlet, and the fourth channel inlet; and a fourth intersection comprising the second cylinder port, the fourth channel outlet, and the fifth channel inlet.