. 2011 Jun;6(2):112–125.

Table 3.

Summary of intervention studies aimed at quadriceps strengthening.

Study, Type, Level of Evidence	Intervention	% decrease in pain	Effect Size
Bakhtiary & Fatemi⁴² QE (Level 2)^a	Group 1 (n=16): straight leg raise exercise	26	.31
Bakhtiary & Fatemi⁴² QE (Level 2)^a	Group 2 (n=16): single-leg semi-squat exercise	26	.24
Bily et al⁴⁵ RCIT (Level 2)^a	Group l(n=18): combination of non-weight bearing and weight bearing hip and knee strengthening exercise⁸²	75	.50
Bily et al⁴⁵ RCIT (Level 2)^a	Group 2 (n=18): same exercise program as above plus 2 20-minute daily sessions of electrical stimulation	73	.50
Dursun et al⁴⁶ RCT (Level 2)^a	Group l(n=30): combination of non-weight bearing and weight bearing quadriceps exercise and stationary bike plus biofeedback	84	.93
Dursun et al⁴⁶ RCT (Level 2)^a	Group 2 (n=30): same as group 1 except no biofeedback	90	.93
Hazneci et al⁸³ QE (Level 2)^a	All subjects performed isokinetic knee extension exercise (1 group n=24)	52	.83
Herrington & Al-Sherhi⁴⁴ RCT (Level 2)^a	Group l(n=15): non-weight bearing knee extension exercise	44†	.56
	Group 2 (n=15): seated leg press exercise	61†	.83
	Group 3 (n=15): control	−20†β	.30
Loudon et al¹³ RCT (Level 2)^a	Group 1 (n=9): combination of non-weight bearing and weight bearing exercise performed in a PT clinic	59	N/A
	Group 2 (n=9): combination of non-weight bearing and weight bearing exercise performed as a home exercise program	43
	Group 3 (n=11): control	8
Song et al⁴³ RCT (Level 2)^a	Group 1 (n=27): combined leg-press and hip adduction exercise	45	.42
	Group 2 (n=27): leg-press exercise	53	.48
	Group 3 (n=25): control	4	.04
Syme et al⁴¹ RCT (Level 2)^a	Group l(n=21): selective vastus medialis oblique exercise	55	.43
	Group 2 (n=22): general quadriceps femoris exercise	45	.37
	Group 3 (n=20): control	17	.23
Witvrouw et al¹¹ RCIT (Level 2)^a	Group 1 (n=30): non-weight bearing knee extension exercise	47	.39
Witvrouw et al¹¹ RCIT (Level 2)^a	Group 2 (n=30): weight bearing knee extension exercise	54	.43
Witvrouw et al⁶⁶ PR (Level 2)^a	Group 1 (n=24): non-weight bearing knee extension exercise	71	.59
Witvrouw et al⁶⁶ PR (Level 2)^a	Group 2 (n=25): weight bearing knee extension exercise	51	.45

QE = quasi-experimental

RCT = randomized control trial

RCIT = randomized clinical trial

PR = prospective randomized

PFPS = patellofemoral pain syndrome

PT = physical therapy

N/A = unable to calculate since standard deviations were not reported

a = Level 2 (limited-quality patient-oriented evidence)

† Pain assessed using a 100-mm visual analog scale during a step-down test

β Represents an increase in pain