Appendix.

Pearson Product Moment Correlation Matrix for All Predictor Variables, r (P) ^a

Variable	Presurgery							Postsurgery
	MVIC			CAR		QI	KOOS Pain	MVIC		QI	CAR		QI	KOOS Pain
	Injured Limb	Uninjured Limb	QI	Injured Limb	Uninjured Limb			Injured Limb	Uninjured Limb		Injured Limb	Uninjured Limb
Presurgery
MVIC
Injured limb
Uninjured limb	0.57 (.05)
QI	0.54 (.10)	−0.14 (.53)
CAR
Injured limb	0.18 (.42)	−0.14 (.55)	0.30 (.19)
Uninjured limb	0.13 (.57)	0.20 (.33)	0.00 (.99)	0.38 (.09)
QI	0.06 (.79)	−0.33 (.15)	0.39 (.08)	0.74 (.01)	−0.20 (.39)
KOOS pain	0.01 (.96)	−0.07 (.74)	–0.09 (.68)	−0.31 (.18)	−0.34 (.13)	−0.20 (.39)
Postsurgery
MVIC
Injured limb	0.19 (.41)	−0.02 (.93)	−0.06 (.77)	0.12 (.59)	0.06 (.79)	−0.0 (1.94)	0.21 (.38)
Uninjured limb	0.13 (.57)	0.24 (.29)	−0.17 (.47)	−0.05 (.87)	0.02 (.90)	−0.18 (.44)	0.15 (.52)	0.82 (.00)
QI	0.38 (.09)	−0.07 (.75)	0.31 (.18)	0.25 (.28)	0.35 (.12)	−0.08 (.71)	0.14 (.53)	0.30 (.19)	−0.08 (.73)
CAR
Injured limb	0.00 (1.0)	−0.08 (.73)	0.06 (.77)	0.04 (.86)	0.11 (.63)	−0.07 (.74)	−0.03 (.88)	0.37 (.10)	0.20 (.38)	0.10 (.66)
Uninjured limb	0.23 (.31)	−0.06 (.78)	0.31 (.18)	0.11 (.61)	0.28 (.21)	−0.12 (.59)	−0.14 (.55)	−0.34 (.14)	0.34 (.14)	0.26 (.25)	0.46 (.03)
QI	0.23 (.31)	0.04 (.95)	−0.23 (.31)	−0.21 (.35)	−0.17 (.47)	−0.12 (.58)	−0.01 (.95)	0.00 (.98)	−0.05 (.51)	−0.17 (.40)	0.54 (.02)	−0.34 (.13)
KOOS pain	0.07 (.75)	−0.33 (.12)	0.33 (.15)	0.13 (.58)	0.04 (.86)	0.18 (.43)	0.04 (.85)	0.38 (.14)	0.36 (.11)	0.40 (.07)	0.22 (.33)	0.12 (.59)	0.22 (.34)

Abbreviations: CAR, central activation ratio; MVIC, maximal voluntary isometric contraction; QI, quadriceps index.

^aSignificant at P ≤ .05. Correlation coefficient (r) classified as weak (0–0.4), moderate (0.4–0.7), or strong (0.7–1.0). Boldface text indicates a significant correlation at P < .05.