Fig. 1: The muscle mass and function of the quadriceps significantly decline during the progression of OA in the affected joint.
a, The X-ray image depicts a patient suffering from severe unilateral OA. M, muscle. b,c, The muscle quality of the quadriceps, including thigh circumference (b) and muscle strength and QST (c), was assessed in both the contralateral and affected sides of patients with unilateral OA (n = 15). d, Musculoskeletal ultrasound analysis of the cross-sectional diameter of RF combined with VI, or VI alone, in patients with severe unilateral OA (n = 15). e, Aged mice (21 months) with spontaneous unilateral OA were used to investigate muscle quality. The CSA of the quadriceps was quantified using WGA staining (n = 5). f, Contractile properties analysis was conducted on aged mice, and data of the normalized single-twitch force (sPt), the maximum isometric tetanic force (sPo) and the tetanic force, as well as the peak tetanic force, are shown (n = 5). g, Illustration of quadriceps quality analysis. h, Mass quantification of quadriceps in mice with DMM (n = 10) or sham (n = 9) surgery. i, H&E staining and immunostaining for the total myofibers, MyHC-IIa fibers and MyHC-IIb fibers of quadriceps cross-sections in mice at 12 weeks after DMM or sham surgery. Represented images were selected from sections of the quadriceps above (n = 6 sham, n = 5 DMM). j,k, Quantification of i, including CSA distribution (j) and mean CSA (k) (n = 6 sham, n = 5 DMM). l, Experimental scheme of gait analysis and contractile testing. m, Scheme of the measurement methodology for RH-dual stance. n, Data of RH-dual stance in mice with DMM or sham surgery (n = 10 sham (4 weeks) and sham (12 weeks), n = 13 sham (8 weeks), n = 11 DMM (8 weeks) and DMM (12 weeks), n = 16 DMM (4 weeks)). o, The contractile properties analysis for mice after DMM (n = 4) or sham (n = 4) surgery. Data are presented as mean ± s.e.m. unless otherwise noted; all statistical tests were two-sided unless otherwise noted; and n represents biological replicates unless otherwise noted. Paired t-test (b,c (muscle strength), d–f (sPt), f (sPo)). Wilcoxon signed-rank test (c (pression strength)). Student’s t-test (h,k,n,o (sPt), o (sPo)). Two-way ANOVA with Bonferroni test (f (peak tetanic force), j,o (peak tetanic force)). Median (25% IQR, 75% IQR; c (pression strength)). IQR, interquartile range; w, weeks; UN, unidentified; LF, left foot; LH, left hand; RF, right hand.
