JOA - 2026-09-04 - Journal Article
Heterogeneity of Quadriceps Muscle Volume in Knee Osteoarthritis: A Latent Profile Analysis and Its Clinical Implications for Arthroplasty Outcomes.
Yang Y, Zang W, Zhou Y, Chen Y, Waterson B, Zhu J, Zhu C, Zhang X
Topics
Key Takeaway
Latent profile analysis of preoperative CT-derived quadriceps volumes identified three distinct muscle phenotypes in TKA patients, with the highest-volume class (n=27) achieving the best absolute WOMAC improvement (41.8 points) and the lowest-volume class (n=39) showing the least VAS improvement (2.8 points) at six months.
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Summary
This retrospective study used CT-derived quadriceps volumetric ratios (rectus femoris/intermedius, vastus medialis, vastus lateralis normalized to femoral volume) and latent profile analysis to classify 191 robot-assisted primary TKA patients into three muscle phenotype subgroups. All three classes demonstrated significant WOMAC and VAS improvement at six months (all P<0.05), but class × time interactions were significant (P<0.001) for both WOMAC and VAS, indicating divergent recovery trajectories. The preserved-muscle class achieved the best absolute outcomes (WOMAC improvement 41.8), while the atrophied class showed the smallest VAS improvement (2.8) despite greater relative functional gains.
Key Limitation
The 76.4% female cohort and single-center robot-assisted TKA design limit generalizability to broader TKA populations, and the absence of a control group receiving standardized versus phenotype-guided rehabilitation prevents causal inference about rehabilitation efficacy.
Original Abstract
BACKGROUND
Knee osteoarthritis (KOA) is characterized by complex structural and muscular alterations. Quadriceps muscle atrophy is a critical, but heterogeneous feature influencing pain, function, and postoperative recovery. Understanding muscle phenotypes may provide novel insight into disease heterogeneity and guide personalized rehabilitation.
METHODS
This retrospective study included 191 consecutive patients undergoing primary robot-assisted total knee arthroplasty (TKA; 76.4% women; mean age 67 years (range 46 to 86)), with preoperative computed tomography (CT) imaging and six-month follow-up. There were three CT-derived quadriceps muscle volumetric ratios (rectus femoris/intermedius, vastus medialis, and vastus lateralis normalized to femoral volume) entered into latent profile analyses (LPA) to identify distinct muscle phenotypes. Associations between latent classes and functional outcomes were evaluated using linear mixed-effects models.
RESULTS
The LPA identified three subgroups: Class 1 (n = 125) with moderate muscle ratios and intermediate function, Class 2 (n = 27) with higher muscle ratios and the best outcomes, and Class 3 (n = 39) with reduced muscle ratios and the worst baseline status. At six months, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC, the improvements of WOMAC in classes 1 to 3 are as follows: 28.6, 41.8, 37.8) and visual analog scale (VAS, the improvements of VAS in classes 1 to 3 are as follows: 3.5, 4.3, 2.8) improved significantly in all classes (all P < 0.05), with significant class × time interactions (all P < 0.001). The range of motion also improved over time (P < 0.001), without a significant class × time interaction (P = 0.562). Overall, Class 2 achieved the best postoperative outcomes.
CONCLUSION
The LPA of preoperative CT-derived quadriceps muscle volumes identified three distinct KOA muscular phenotypes associated with different symptom burdens and recovery trajectories after TKA. Patients who have preserved quadriceps muscles achieved the best absolute outcomes, whereas those who had marked atrophy showed greater relative improvement. These findings support CT-based phenotype-guided perioperative rehabilitation.