JOA - 2026-04-06 - Journal Article
The Impact of Femoral Component Rotation on Patellar Position and Functional Outcomes in Total Knee Arthroplasty.
Leipman JH, Su L, Bash HD, Hohmann AL, Sellig MT, Dipane MV, Boghozian O, Stavrakis AI, Zeegen EN, Fillingham YA, Lonner JH
Topics
Key Takeaway
Femoral component rotation within 3° of internal or external rotation (relative to PCA) produced significantly better Forgotten Joint Scores, KOOS-JR improvement, and ROM compared to components rotated >3° externally, with lateral patellar translation minimized specifically in the 0–3° internal rotation group (P=0.002).
Summary Depth
Choose how much analysis to show on this article page.
Summary
This retrospective multicenter study examined how femoral component rotation relative to the PCA affects patellar kinematics and functional outcomes in conventional and robotic-assisted TKA, stratifying cases from >6° external rotation to 0–3° internal rotation. Patellar translation and tilt differed significantly across rotation groups (P=0.002 and P=0.005); lateral translation was lowest with 0–3° internal rotation, though patellar tilt was paradoxically highest in the 0–3° internal and external rotation groups. FJS, KOOS-JR improvement, ROM, and MCID achievement were significantly better when femoral rotation was within 3° of neutral, with no statistically significant difference between the 0–3° internal and 0–3° external rotation subgroups.
Key Limitation
Sample size and baseline patellar resurfacing status are not reported, making it impossible to determine whether patellar button presence or absence confounds the patellar tilt and translation findings across rotation groups.
Original Abstract
BACKGROUND
Patellar malalignment may occur after total knee arthroplasty (TKA) and can lead to pain and dysfunction. The purpose of this study was to examine the relationship between femoral component rotation and patellar position in TKA.
METHODS
This was a retrospective, multicenter study of patients who underwent conventional or robotic-assisted TKA. In conventional cases, femoral rotation was set to 3° of external rotation relative to the posterior condylar axis (PCA); in robotic cases, femoral component rotation was planned to create balanced flexion gaps and defined relative to the PCA. Pre- and postoperative radiographs were analyzed to determine patellar translation, tilt, and coronal limb alignment. Knee injury and Osteoarthritis Outcome Score-Joint Replacement (KOOS-JR), range of motion (ROM), and postoperative Forgotten Joint Scores (FJS) were collected. Cases were analyzed in incremental groups stratified by femoral component rotation, ranging from greater than 6° of external rotation to greater than 0 to 3° of internal rotation.
RESULTS
Postoperative patellar translation and tilt were significantly different across all femoral rotation groups (P = 0.002, P = 0.005). Compared to all other femoral rotation groups, lateral patellar translation was reduced when femoral components were internally rotated between 0 and 3°. Conversely, those with femoral component internal or external rotation between 0 and 3° had the most postoperative patellar tilt on sunrise radiographs. Postoperative FJS, improvement in KOOS-JR and ROM, and the proportion of patients who met the minimal clinically important difference were significantly better in patients whose femoral components were between 0 and 3° of internal rotation. However, pairwise comparisons with patients who had component external rotation between 0 and 3° demonstrated statistically similar results.
CONCLUSION
Internal and external rotation of the femoral component of up to 3° decreases the likelihood of patellar translation, results in improved functional outcomes and ROM, and leads to improved FJS.