TABLE 2.

VARIABLES ASSOCIATED WITH RETURN TO SPORT

Strong Evidence [54] For Association With Return to Sport	None
Moderate Evidence [54] For Association With Return to Sport	None
Weak Evidence[54] For Association With Return to Sport	Pain		At 1 year post-surgery, patients returning to pre-injury level of sport reported less pain than those who did not return to sport (0.4 versus 1.0 on visual numeric pain scale where 0=no pain, 10=worst pain possible, p=0.05).[69]
			At 3 years post-surgery, 5 of 6 patients with effusion and pain had decreased sports participation level. [60]
	Post-operative quadriceps torque		At 1 year post-surgery, higher quadriceps torque-body weight ratio for patients returning to pre-injury level of sport than those who did not return to sport (81.5% vs. 73.9%, p=0.05).[69]
			At 5 years post-surgery, mean concentric quadriceps torque difference between surgical limb and nonsurgical limb lower in OKC+CKC group than CKC group at 30°/sec (34 Nm versus 60 Nm, p<0.01), 120°/sec (28 Nm versus 39 Nm, p<0.05), 240°/sec (18 Nm versus 27 Nm, p<0.07). Mean eccentric quadriceps torque difference between surgical limb and nonsurgical limb lower in OKC+CKC group than CKC group at 30°/sec (32 Nm versus 76 Nm, p<0.001), 120°/sec (40 Nm versus 65 Nm, p<0.01), and 240°/sec (38 Nm versus 60 Nm, p<0.02). 54.5% of OKC+CKC group returned to sport versus 22.7% of CKC group. [70]
			At mean 7.9 years post-surgery, difference in peak quadriceps torque between surgical leg and nonsurgical leg not different in group with return to pre-injury level of sport (205 Nm versus 226 Nm, p<0.05) but different in group participating in only non-cutting sports (200 Nm versus 241 Nm, p<0.01).[59]
	Knee effusion		At 1 year post-surgery, less effusion for patients returning to pre-injury level of sport than those who did not return to sport. [69]
			At 3 years post-surgery, 5 of 6 patients with effusion and pain had decreased sports participation level. [60]
	Post-operative tibial rotation range of motion		At 2 years post-surgery, higher Tegner activity score correlated with higher tibial internal rotation (r=0.44, p=0.02), higher tibial external rotation (r=0.39, p=0.04) and higher total tibial rotation (r=0.62, p<0.000).[67]
	Episodes of knee instability		At 1 year post-surgery, prevalence of knee instability in patients returning to pre-injury level of sport was less than in those who did not return to sport (44.2% versus 73.8%, p=0.004).[69]
	Marx Activity Score (0=lowest activity, 16=highest activity)		At 2 years post-surgery, higher Marx Activity Score for patients who did return to sport versus did not return to sport (15 versus 7.5, p<0.001).[62]
	Kinesiophobia (TSK score: 0=lowest fear, 51=highest fear) (TSK-11 score: 11=lowest fear, 44=highest fear)		At 1 year post-surgery, lower TSK-11 score for patients returning to pre-injury level of sport than those who did not return to sport (15.3 versus 19.6, p<0.01).[69]
			At 1 year post-surgery, higher TSK score associated with lower likelihood of resuming previous level of activity (β=−0.40); Fear of re-injury unique predictor of return to sport (R2=0.26).[65]
			At 3–4 years post-surgery, lower TSK score for patients with return to pre-injury level of sport versus decreased or no sports activity (15 versus 20, p=0.01).[48]
	Athletic Confidence (ACL-RSI: 0=lowest confidence, 100=highest confidence)		At 6 months post-surgery, higher ACL-RSI for groups with return to pre-injury level of sport than no return to sport (63.18 versus 51.80, p=0.005). At 1 year post-surgery, higher ACL-RSI for groups with full return to sport than no return to sport (72.05 versus 58.61, p=0.001).[68]
			At 1 year post-surgery, higher ACL-RSI for groups with return to pre-injury level of sport versus no return to sport (70 versus 46, p<0.001).[66]
	Self-motivation (Psychovitality questionnaire: (Psychovitality questionnaire: (3=lowest motivation, 18=highest motivation)		Higher pre-operative psychovitality score for group that did return to sport versus did not return to sport at 2 years post-surgery (16 versus 9, p<0.001).[62]
			Higher pre-operative psychovitality score correlated with higher Tegner activity score at 3 years post-surgery (R2 Linear=0,253).[63]
Conflicting Evidence [54] For Association With Return to Sport	Post-operative hamstring torque	Yes	At 1.5–2 years post-surgery, higher hamstring torque correlated with higher Tegner activity score (r=0.52).[61]
		No	At mean 7.9 years post-surgery, difference in max hamstring torque between surgical leg and nonsurgical leg not different in group with return to pre-injury level of sport (107 Nm), mild sports limitation (113 Nm), non-cutting sports (106 Nm), or no sports (104 Nm).[59]
	Hop Testing / Functional Testing	Yes	At 1 year post-surgery, patients with LSI >85% on single leg hop for distance and crossover hop for distance more likely to have attempted pre-injury level of sport than patients with LSI <85% (risk ratio, 2.5; 95% CI, 1.4–4.4).[58]
			At 1.5–2 years post-surgery, faster 6 meter shuttle run test correlated with higher Tegner activity score (r=0.57, p<0.05).[61]
		No	At 1 year post-surgery, no difference between groups with return to pre-injury level of sport and no return to sport in LSI on single hop for distance (91% versus 89%, p=0.371) or cross-over hop for distance (92% versus 92%, p=0.865).[68]
			At 1.5–2 years post-surgery, weak correlations between LSI on single hop for distance (r=0.13, p<0.05), triple hop for distance (r=0.08, p<0.05), cross-over hop for distance (r=0.27, p<0.05), vertical jump test (r=0.15, p<0.05), 10 step climb test (r=0.25, p<0.05), step hop test (r=0.37, p<0.05) and Tegner activity score.[61]
	IKDC Subjective Form Score (0=lowest subjective rating, 100=highest rating)	Yes	At 1 year post-surgery, higher IKDC subjective form score for patients returning to pre-injury level of sport than those who did not return to sport (93.8 versus 78.0, p<0.001).[69]
			At 5 years post-surgery, higher IKDC subjective form score for patients returning to pre-injury level of sport (84.6) than those who did not return to sport due to fear of re-injury (73.5) or due to instability (60.1). (Between groups difference p<0.001).[6]
		No	At 2 years post-surgery, no difference between groups with return to pre-injury level of sport versus decreased sports activity level or no sports activity. [62]
	IKDC Grade (A=normal, D=severely abnormal)	Yes	At 5 years post-surgery, greater percentage of patients returning to pre-injury level of sport (89.3%) had IKDC Grade A&B scores compared to those who did not return to sport due to fear of re-injury (77.7%) or due to instability (50%). (Between groups difference p=0.028).[6]
		No	At 1 year post-surgery, no difference in return to sport outcomes between patients with IKDC Grade A and B (risk ratio, 1.5; 95% CI, 0.81–1.40). No difference in return to sport outcomes between patients with IKDC Grade A&B and IKDC Grade C&D (risk ratio 1.5; 95%CI,0.86–2.50).[58]
			At 2 years post-surgery no significant difference between groups with return to pre-injury level of sport versus decreased sports activity level or no sports activity. [62]
	Lysholm Knee Score (0=worst function, 100=highest function)	Yes	At 5 years post-surgery, higher Lysholm Knee score for patients returning to pre-injury level of sport (88.5) than those who did not return to sport due to fear of re-injury (84) or due to instability (72). (Between groups difference p=0.001).[6]
			At 1.5–2 years post-surgery, no correlation with Tegner activity score. [61]
			At 2 years post-surgery, no difference between groups with return to pre-injury level of sport versus decreased sports activity level or no sports activity (p=0.38).[62]

OKC=open kinetic chain; CKC=closed kinetic chain; TSK=Tampa Scale of Kinesiophobia; ACL-RSI=Anterior Cruciate Ligament-Return to Sport after Injury Scale; LSI=limb symmetry index; IKDC = International Knee Documentation Committee