Table 3. Summary of studies and their main results on muscle strength and knee pain.

Study	SAMPLE				GI	GC	Duration	Analyzed variables
	SAMPLE	MEN	AGE	GROUPS				PAIN	MUSCLE STRENGTH
Lim et al., 2008 33	107	48	53–73 years old	GI: 54 GC: 53	Quadriceps strengthening with weighted shin sleeves and Theraband	No intervention	12 weeks	Significant pain improvement in the group with better knee alignment	NA
K.L. Bennell et al., 2010 25	102	51	62–73 years old	GI: 51 GC: 51	Hip strengthening l (quadriceps adduction, external rotation, extension and isometry)	No intervention	12 weeks	Pain improvement in GI compared to GC	Significant hip and quadriceps strength improvement compared to the control group
G. Kelley Fitzgerald et al., 2011 20	183	61	63–73 years old	GI:92 GC: 91	The agility and disturbance group received the same standard exercise program with the addition of training techniques on agility and disturbance	Standard exercise program: an exercise program including muscle stretching, strengthening and walking on a treadmill	4 years and 2 months	Both groups presented modest improvements, but with no significant differences between them	NA
Saccomanno MF et al., 2016 21	165	44	40–70 years-old	GI-1: 53 GI-2:53 GC: 51	GI-1: three hyaluronic acid (HA) injectionsGI- 2: HA injections + knee exercises	Knee exercises	6 months	At the 1 st month, GI-2 scores were significantly better compared to GI-1. GC and GI-2 presented a significant reduction at the 1 st and the 6 th month	NA
Palmer S et al., 2014 22	224	83	60–72 years old	GI:73 GC-1: 74 GC-2: 77	Active TENS (continuous mode, – 110 Hz, 50 µs) + knee exercises	GC-1: fictional TENS + knee exercises GC-2: knee exercises (30 minutes of education + 30 minutes of exercises)	6 weeks	Each score from each group significantly improved over time	NA
Holsgaard-Larsen A et al., 2017 23	93	39	40–70 years old	GI: 47 GC: 46	Warming up (10 minutes), functional, proprioceptive training, resistance strengthening and cooling down	Information about analgesic and anti-inflammatory agents	8 weeks	There were no significant differences between groups	NA
Jorge RT et al., 2015 24	60	NA	40–70 years old	GI: 29 GC:31	Warming up, 5 minutes at bike. Progressive resistance exercise (knee extension/flexion and hip adduction and abduction with light weights).	No intervention	13 weeks	Pain in the GI group was significantly lower in 45 and 90 days	Significant differences for hip adduction between groups from T0 until the end of the study

Abbreviations: GC, control group; GI, intervention group; NA, not analyzed; TENS, transcutaneous electrical neural stimulation; T0, initial time.