The investigators are comparing the range of movements the knees of patients who had total knee replacement surgery for knee osteoarthritis. In the study arm, the implant used was a Sigma Cruciate Retaining (CR) Press Fit Condylar (PFC) 150, which is a high flexion knee system designed to combine function with wear resistance. It can accommodate up to 150 degrees of knee flexion. In the cohort arm, the implant used was the standard Sigma CR which can accommodate up to 120 degrees of flexion.

Both sets of patients will undergo routine post-operative follow up in clinic. The study involves patients who had their surgery more than 2 years ago. We assess their range of movement using fluoroscopy. They are asked to perform lunges, squats and climbing up and down 3 steps. The fluoroscopic images are then analysed to assess their individual range of movements.

Inclusion Criteria:

• All patients who underwent total knee replacement surgery who received either the PFC CR 150 knee implants or the PFC CR standard knee implant
• Surgery more than 2 years
• Able to walk, climb stairs

Exclusion Criteria:

• Knee stiffness with less than 100 degrees of knee range of movement
• Patients who required revision surgery
• Patients who received an all polyethylene tibial insert
• Patients who received rotating platform tibial tray

All patients who underwent total knee replacement surgery who received either the PFC CR 150 knee implants or the PFC CR standard knee implant