Effect of Preoperative Diabetes on the Achievement of Forgotten Knee Status in Patients with Total Knee Arthroplasty.

Background: Forgotten knee is the terminology which is used to describe a post-TKA patient who is completely unaware of his knee implant. The aim of the study is to determine whether preoperative diabetes negatively influences the achievement of forgotten knee status.

Methods: This is a retrospective cohort study. 300 patients (240 F:60 M) were studied. Patients were evaluated by an independent observer with FJS-12 score 2 weeks preop and at 6 weeks and 12 months after the operation. The patients with a FJS-12 score of ≥ 55 were considered to have achieved forgotten knee status. Out of 240 females, 96 had diabetes and out of 60 males, 18 had diabetes. Preoperative factors such as preop HBA1c, ROM, degree of deformity, VAS score and other associated co morbidities and postoperative factors such as HBA1c, ROM and hip-knee-ankle alignment were studied. Study was started with null hypothesis. The statistical difference was measured with Binominal proportion test and comparison of means test.

Results: 96 out of 144 non-diabetic females (66.67%) and 51 out of 96 diabetic females (53%) achieved forgotten knee status (statistically significant, value = 0.0336, Binominal proportion test). 27 out of 42 (65%) non-diabetic males and 12 out 18 diabetic males (66%) achieved forgotten knee status ( value = 0.9411). The FJS-12 score at 1 year for non-diabetic females and diabetic females was 58.6 mean ± 12.6 SD and 53.8 ± 17.6, respectively, which is statistically significant, value 0.0145. The FJS-12 at 1 year in non-diabetic and diabetic males was 60.1 ± 14.8 and 59.6 ± 17.3, respectively, value = 0.9097.

Conclusion: Diabetic females have less chance of achieving a forgotten knee status than non-diabetic females. This understanding will help the operating surgeon in the preoperative patient counseling and modify the patient expectations.