Functional Outcome of Vanguard XP vs CR: a single centre RCT using three dimensional fluoroscopic analysis

• Patient with non-inflammatory knee osteoarthritis, which is confirmed by radiology.

• Osteoarthritis is unilateral or bilateral with the contralateral knee functioning properly, not operated on in the last 6 months and not planned for TKA in the coming 2 years.

• Patient is set to receive a primary cemented total knee arthroplasty.

• Age between 40 and 75 years, inclusive, on the day of the operation.

• Patient plans to be available for follow-up until two years post-operative.

• Patient is in stable health (ASA-score ≤ 3) and is free of or treated for cardiac, pulmonary, haematological, or other conditions that would pose excessive operative risk.

• Patient has a correctable or <10° rigid (non-correctable) varus or valgus deformity of the knee.

• Participants must be able to give informed consent.

• Patient has a BMI > 35.

• Patient's expected physical activity after surgery is 2 or less on the UCLA Activity Scale.


• Patient has had previous hip replacement surgery in the last 6 months, or is planned to have a hip replacement in the next 6-12 months (because of the effect on function).

• Patient has had major, non-arthroscopic surgery to the study knee, including HTO.

• Patient has an active, local infection or systemic infection

• Prior high-energy trauma to the affected knee or prior history of anterior and/or posterior cruciate ligament rupture.

• Suspicion of anterior and/or posterior cruciate ligament rupture at clinical examination.

• Documented osteoporosis with patient in active medical treatment.

• Patient has physical, emotional or neurological conditions that would compromise compliance with post-operative rehabilitation and follow-up.

• Bone quality compromised by disease or infection which cannot provide adequate support and/or fixation to the prosthesis

• Severe instability of the knee joint secondary to the absence of collateral ligament integrity and function

• Patient has knee flexion < 90 degrees

• Patient has fixed flexion deformity >10 degrees (passive extension lag)

• Patient has > 30 degrees extension deficit (active restraint to extension)

• Patient does not have a proper functioning patella tendon on the affected side; measured as inability of active extension of the knee

• Patient has quadriceps weakness on the affected side; score on MRC scale < 4 measured by research nurse

• Patient has rheumatoid arthritis, any auto-immune disorder, immunosuppressive disorder or a terminal illness.