Hatfield GL, et al. - Experts aspired to explore whether baseline quadriceps and hamstrings muscle activity patterns varied between those with medial-compartment knee osteoarthritis who advanced to total knee arthroplasty (TKA) and those who did not, and to test connections between features extracted from principal component analysis (PCA) and discrete measures. From 54 people with knee osteoarthritis during walking, vastus lateralis and medialis, rectus femoris, and lateral and medial hamstrings surface electromyograms were obtained. Twenty-six candidates reported undergoing TKA at follow-up 5-8 years later. The authors discovered that the TKA group had higher hamstrings activity magnitudes (PC1), prolonged activity in mid-stance (PC2) for all muscles, and greater lateral co-contraction indices. For all stance phases, TKA had higher hamstrings root mean square (RMS) activity, and higher mid and late-stance quadriceps RMS activity. Findings revealed that those who advanced to TKA had higher magnitudes and more prolonged agonist and antagonist activity, consistent with less joint unloading. Such gait muscle activation patterns suggest a potential target for conservative intervention.