Bone defects are a challenge to any and in fact every orthopedic surgeon, be they as a consequence of trauma, peri-implant bone loss as is the case in revision surgery or, more often than not, in tumors of the bone. These defects are in most cases difficult to reconstruct, but even more so in the case when they are located around the major joints of the lower limb, i.e. the hip and the knee. We focus in this article on acetabular bone defects as well as on defects around the knee (distal femur and proximal tibia). We present implant possibilities and modern means of reconstructing the bone defect using augments. We also present three representative cases from our Clinic, to further exemplify the discussed concepts. We present our opinions on reconstructing bone defects after tumor and revision surgery in the hip and knee and we draw conclusions.