Abstract Prosthetic instability is the third most frequent cause for the failure of total knee replacement (TKR), which leads to between 10% and 22% of surgical revisions. In addition to individual factors such as previous instabilities or deformities, an associated neuromuscular condition, rheumatoid arthritis or obesity, the main causes for prosthetic instability are related to errors in selecting the primary prosthesis or mistakes in the surgical technique, i.e. inadequate bone resections, failure to obtain an appropriate joint balance with symmetrical flexion and extension gaps, causing a iatrogenic laxity, etc. - all of them easily preventable. In order to successfully correct these instabilities, it is indispensable to identify its causes so as to be able to address and thereby avoid repeating the same mistakes that provoked them in the first place. As, the majority of cases will require surgical treatment and prosthetic revision, in this study we carry out an analysis of the different models available. As a general rule, we recommend the use of a prosthetic model with the minimum constraint necessary to achieve stability, taking into account that a posterostabilized prosthesis may be able to address a flexion instability, although it cannot compensate for a medial-lateral instability, and that even if a highly constrained prosthesis can compensate for both instabilities initially, in the long term it can lead to mechanical complications.