Abstract The articulating surface of standard femoral knee component is as generic shape while every individual patient has a unique shape of knee joint and this is causes some problems. The Conventional femoral knee component gives a satisfactory result in many cases that carry the patient back to active lifestyle and near normal patient and especially for younger patients. Most patients' gaits are altered after a total knee replacement (TKR) due to the change in surface geometry of femoral implant. The main objective of this work is to design custom design implant as smooth-implant interface of femoral component to increase appropriate bone ingrowths and to prevent bone remodeling found in conventional knee implants, also this design maintain the articulating surface of femoral with tibial component and patellar component as natural knee to maintain the patients gait without altered. This custom design of femoral knee implant will provide better results for patients who have more active lifestyle and strenuous activities such as younger patients. The custom design was done by creating 3D models from computerized tomography (CT) scan data through computer segmentation using Materialise MIMICS software. Geomagic studio software was used in this work for smoothing, preparation of the model and convert STL file format to STEP format. The 3D model as STEP format then exported from Geomagic Studio to CAD design software such as solidworks (Solidworks, USA) for design on the femoral components of the implant. From 3D model of the femur, a custom knee implant femoral component was designed. Finite Element Analysis was used to examine and evaluate the stress distribution over the interface between the implant and femur bone. The custom design as smooth surface describe a more even stress distribution in the contact region between femur bone and implant. This stress will reduce the uneven bone remodeling; also reduce the risk of premature loosening of implant