Catherine A. Tonks, DVM 1 , Antonio Pozzi, DMV, MS, Diplomate ACVS 1 , Hang-Yin Ling, PhD 2 , and Daniel D. Lewis, DVM, Diplomate ACVS 1 1 Comparative Orthopaedics Biomechanics Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL and 2 Department of Orthopedics and Rehabilitation, College of Medicine, Universit Veterinary Surgery April 2010 39 3 343-349 ABSTRACT Objective: To determine the effect of suture tension on contact pressures in the lateral compartment of the stifle for the TightRope CCL® (TR) and circumfabellar–tibial suture (LS) techniques. Study Design: Ex vivo biomechanical study. Sample Population: Pelvic limbs (n=12) from dogs weighing 21–24 kg. Methods: A pressure sensor was used to record peak contact pressure (PCP) and mean contact pressure (MCP) and contact area (CA) in limbs mounted in a materials testing machine. Stifles were stabilized using either a TR or LS technique and the prosthesis was tensioned increasingly from 25 to 70 N. PCP, MCP, and CA were collected at each applied tension before and after applying an axial load of 150 N. Results: In the unloaded condition, LS stabilization resulted in a significant increase (P=.034) in PCP at ≥40 N tensions, whereas TR stabilization resulted in a significant increase (P=.047) in PCP at 70 N tension. There was a significant increase in CA at tensions ≥60 N in the LS group. No effect on MCP was noted. No significant differences in contact pressures were observed in the loaded condition. There were no significant differences in normalized PCP and CA between stabilization groups at any of the tension increment. Conclusions: The application of high tension to the extra-articular prosthesis alters lateral compartment contact pressures in the unloaded stifle in this ex vivo model. Clinical Relevance: Over tightening of an extra-articular prosthesis may increase lateral compartment pressure at the time of surgery. The clinical implications of this finding are unknown, as weight bearing may negate any detrimental effect of high prosthesis tension.