A prosthetic knee joint with buffering and braking effects has an upper connecting base, a linking assembly, a braking assembly, and a lower connecting base. The upper connecting base has two extending lugs and an accommodating recess. The linking assembly has two linking arms respectively and pivotally connected to the upper connecting base. The braking assembly has a braking arm protruding into the accommodating recess of the upper connecting base and pivotally connected to the two extending lugs. The lower connecting base is connected to the linking assembly and the braking assembly. The upper connecting base, the linking assembly, the braking assembly and the lower connecting base form a four-bar linkage. A cushion between an abutter and a main body provides a buffering effect during walking. Thus, the prosthetic knee joint has simplified structure and reduced cost and is convenient in assembly and use.
