Introduction and Aims: To determine whether sagittal laxity has an effect on functional outcome following posterior cruciate retaining total knee replacement using two differing tibial insert designs.

Method: Ninety-seven knees in 83 patients were reviewed clinically, radiologically and underwent KT1000 testing at minimum five-year follow-up post-TKA. Knee society, WOMAC and SF12 scores were calculated. The same femoral component (Duracon, Stryker) was used in all patients. Two differing tibial inserts were used (51 Condylar and 46 AP lipped).

Results: The two groups were comparable for age, sex, Charnley category and Body mass index. There was no significant difference in knee society score, WOMAC scores, SF12 scores, knee flexion, posterior tibial slope or KT1000 laxity measurements between the two groups. Total laxity measured by KT1000 was 5mm in the AP lipped group and 4mm in the condylar group. There was no correlation between anterior, posterior or total laxity and functional outcome as measured by WOMAC, KSS, SF12 or knee flexion.

Conclusion: Increased sagittal laxity does not have a strong influence on functional outcome following TKA. The differing tibial insert designs had no significant influence on laxity or function.

To determine whether increased sagittal laxity has an effect on functional outcome following posterior cruciate retaining total knee replacement using two differing tibial insert designs.

Ninety-seven patients were reviewed clinically, radiologically and underwent KT1000 testing of their TKR at a minimum follow up of 5 years (mean 6.5 yrs). The femoral component design was the same in all patients (Duracon/PCA). Fifty two patients had a relatively flat tibial insert design (group 1), while 45 patients had an AP lipped insert (group 2) following a change in design in 1995.

The 2 groups were comparable for age, sex, Charnley category, BMI, tibial slope and follow up. There was no significant difference in laxity measurements, IKS or WOMAC scores between the groups. There was no significant correlation between laxity and outcome score or flexion range.

Increased sagittal laxity in a knee replacement does not have a strong influence on functional outcome. The differing tibial insert designs had no significant effect on either laxity or function.