BACKGROUND: The global increase in revision total knee arthroplasties (rTKA) imposes a significant healthcare challenge. As instability is one of the leading indications, a standardized preoperative assessment of the knee stability is imperative. This study used the Telos Stress Device (TSD) to evaluate coronal laxity in patients scheduled for rTKA, (1) aiming at assessing measurement reliability in order to standardize TSD usage in the preoperative evaluation, (2) evaluating varus and valgus laxity in rTKA patients and comparing them to those of the primary TKA population, and (3) investigating if the objective joint laxity varies among instability, malalignment or aseptic loosening as indications for revision. MATERIAL AND METHODS: Twenty seven patients undergoing rTKA in 2022-2023 were included. Standardized coronal stress radiographs (150N) in 10-20° flexion and in supine position were captured using the TSD before revision surgery. Two independent raters measured the angulation between the femoral and tibial components on all radiographs, with valgus laxity defined as a lateral force applied while evaluating the medial joint opening, and varus laxity defined as the opposite. (1) Reliability was evaluated using intra-class correlation coefficient (ICC). (2) The laxity values in the study population were interpreted and compared to the general TKA population based on a literature review. (3) Laxity measurements were compared across instability, malalignment and aseptic loosening as indications for revision, with an emphasis on the correlation between alignment and laxity measurements. RESULTS: (1) Excellent inter- (ICC = 0.983) and intra-rater reliability (ICC = 0.992 and ICC = 0.983) were observed. (2) Mean valgus and varus laxity in patients scheduled for revision were 5.8° (SD, 3.3) and 4.9° (SD, 4.1), respectively. Valgus laxity in patients scheduled for revision TKA differed significantly from the observed postoperative valgus laxity (4°) in the general TKA population without need for revision, while varus laxity was comparable. (3) No significant difference in laxity were noted among instability, malalignment and aseptic loosening as indications for revision. A significant correlation was found between valgus laxity and mLDFA (p = 0.031). CONCLUSION: This paper revealed that for revision patients valgus laxity is notably higher compared to the general TKA population. Increased valgus laxity may therefore play an important role in patient dissatisfaction following total knee arthroplasty. As revision surgery is no exploratory surgery, all information necessary should be objectively collected via a standardized protocol, especially when the role of instability in symptoms is uncertain. Telos stress testing can be easily implemented in this flow and is highly reliable.