Flexion and anterior knee pain after high flexion posterior stabilized or cruciate retaining knee replacement.

BACKGROUND Special high-flexion prosthetic designs show a small increase in postoperative flexion compared to standard designs and some papers show increased anterior knee pain with these prosthesis. METHODS A prospective double blind randomized controlled trial investigates the difference in flexion and anterior knee pain between standard and high-flexion total knee arthroplasty. In total 47 patients were randomly allocated to a standard cruciate retaining fixed bearing design (CR) in 23 patients and to a high-flexion posterior stabilized mobile bearing design (HF-PS) in 24 patients. RESULTS The HF-PS did show a significantly higher passive postoperative flexion; 120.8° (SD 10.3°) vs. 112.0° (SD 9.5°) for the CR group (p = 0.004). The active postoperative flexion, VAS-pain score and Feller score did not show significant differences between both groups. Sub analysis with the HF-PS group showed a higher VAS-pain for the patients achieving ≥130° of flexion; 30.5 (SD 32.2) vs. 12.2 (SD 12.5) (p = 0.16). CONCLUSION The present study showed a significant higher passive flexion in the high-flexion prosthesis compared to the standard prosthesis. However this difference disappeared when comparing active flexion. No difference in anterior knee pain was found between both groups.