A link arm for connecting a first unsuspended mass to a second suspended mass, and its manufacturing method are provided. In some embodiment the arm applies in particular to a suspension system for a motor vehicle, wherein the arm is able to equip a wheel suspension by having triangular housings to receive a stub axle of the wheel and two connecting links to the chassis of the vehicle. In some embodiments, the arm comprises housings to receive a first linkage joint to the first mass, and at least a second linkage joint to the second mass, and comprises: a stiffening portion which comprises a first thermoplastic or thermosetting matrix composite material reinforced with fibers and which comprises a peripheral rim of the arm, and an anti-buckling portion interposed in the stiffening portion and extending from the rim over substantially the entire arm.