Objectives: There have been no manuscripts to compare the bone ingrowth between CR type (Cruciate Retaining) and PS type (Posterior Stabilized) of cementless total knee arthroplasty(porous tantalum metal modular tibial component) and evaluate by imaging the postoperative computed tomography. The purpose of this study was to clarify and compare the bone ingrowth under the peg of porous tantalum modular tibial component between CR and PS. Methods: A consercutive series of 46 total knee arthroplasties (CR:23,PS:23) were reviewed prospectively. We was divided mediolaterally into six regions under the peg of tibial component and analyzed bone mineral content/total volume (BMC/TV)values using 3D osteomorphometry software with MDCT under lower the knee every 3 months(follow-up:21 months). Results: There were significantly higher BMC/TV values for PS typethan CR type at ROI.2.4.6 (Lateral, Lateral-Anterior, Lateral-posterior) at 3.18.21 months postoperatively. There were not a significant difference in the relative change in BMC/TV values in ROI.1.3.5 (Materal, Materal-Anterior, Materal-Posterior). Conclusions: The study indicated that PS type associated with the post-cam mechanism and midflextion instability was caused reactive cancellous stabilized and not occrred the influence of stress shieldings in lateral site under the peg of tibial component than CR typepost-operatively18 months later.