A coupler assembly for detachably coupling an arm to a work tool. The coupler assembly comprises a first linkage having an idle link and a power link, a first pin provided on the arm, and a second pin provided on the power link. The first and second pins are receivable in openings on the work tool. The coupling assembly is characterized by a second linkage provided between the first and second pins comprising a first link and a second link joined at a shaft. The first link is fixed to the shaft to prevent rotation therebetween. A portion of the shaft comprises a gear. The second link comprises a body mounted on the shaft so as to be rotatable thereabout, the body comprising a chamber in which a piston is received, the piston including a geared section that is meshed with the gear.