this study is to compare the posterior condylar offset , posterior condylar offset ratio and tibial slope of Egyptian population with Asian and Western results.These results may be important to examine if contemporary total knee arthroplasty components match the anatomy of Egyptian populations or they are significantly different with the need of different prosthesis designs and geometrics.

Lateral knee x rays will be collected from the registry system of Assiut University Hospital through Paxera pacs system . Posterior condylar offset, posterior condylar offset ratio and tibial slope will be measured from the x rays.

In the sagittal plane, the femoral long axis will be drawn with equal distance to the anterior-posterior edges of the femoral shaft. One line will be drawn parallel to the anterior femoral shaft cortex and another parallel to the posterior femoral shaft cortex. A third line will be drawn parallel to the posterior femoral shaft cortex line, but tangent to the most posterior femoral condyles to represent the posterior condylar tangent line. The anterior-posterior dimension of the distal femur is defined as the distance between the anterior femoral shaft cortex line and the posterior femoral condyle tangent line . The posterior femoral condyle offset (PCO) is determined as the distance between the posterior femoral shaft cortex line and the posterior femoral condyle line, that is noted as PCO .The posterior femoral condyle offset ratio (PCOR) is calculated as the ratio of the posterior femoral condyle offset and the anterior-posterior dimension of the distal femur, i.e., PCO/ACP.

Tibial slope will be measured as follows; the tangent to the medial tibial plateau is considered to be the proximal reference line. This is the line connecting the highest anterior and posterior points of the medial plateau. The second reference is the axis of the tibia, defined as a line through the middle of the shaft at 10 and 20 cm. The angle between these two lines is the tibial slope.

Data of the cases will be collected as name, age and gender. The results will be collected and will be compared with those of Asian and Western results. These results may be important to examine if contemporary TKA components match the anatomy of Egyptian populations or they are significantly different with the need of different prosthesis designs and geometrics.

Inclusion Criteria:

• Proper lateral knee x ray of adult cases

Exclusion Criteria:

• 1. Improper x ray projection
• 2. Retained hardware
• 3. Malunited distal or upper tibia fracture

all adult cases who have proper lateral knee x ray on the registery system of Assiut University Hospital , will be collected. These x rays will be used in this study as posterior condylar offset, posterior condylar offset ratio and tibial slope will be measured on these x rays