The influence of joint line restoration on functional outcome after primary total knee arthroplasty: A prospective...

Restoration of proper joint line position after primary total knee arthroplasty (TKA) is important for improved knee function and kinematics. We reviewed the magnitude of joint line alteration and the resulting effect on post-operative knee outcomes scores at one year follow-up.

120 patients who underwent TKA for primary osteoarthritis knee were included. Assessment of joint line position before and after surgery was performed with the help of bony landmarks (excluding osteophytes): Medial Epicondyle Joint Line distance (MEJL), Lateral Epicondyle Joint Line distance (LEJL) and Fibula Head Joint Line distance (FHJL) were calculated. Post-operative knee function was assessed using 'The Western Ontario and McMaster Universities Arthritis Index' (WOMAC) and 'Knee Society Score' (KSS) at one year follow-up.

Joint line elevation was observed in 104/120 (86.7%) patients and 16/120 (13.3%) patients had no joint line elevation. The mean joint line elevation was 3.00 (±2.13) mm. The patients were sub-classified into two study groups: Group A- Joint line elevation <5 mm and Group B- Joint line elevation ≥ 5 mm. The mean post-op one-year KSS score was significantly higher in patients in Group A compared to Group B (52.82 ± 7.564 vs. 40.73 ± 7.146; p < 0.001). The mean post-op one-year WOMAC score was lower in patients in Group A compared to Group B (65.51 ± 14.762 vs.75.64 ± 8.203) and the difference was statistically significant (p = 0.002).

Elevation of joint line ≥5 mm from the pre-operative value has a negative impact on post-operative functional outcome in primary TKA.