Table 1.

Study characteristics of the included studies

Study	Design	Location	Drug type	Inclusion criteria	Experimental group 1	Experimental group 2	Control group	Age (yrs)	Sex (M/F)	Outcome	Follow-up
Benito-Ruiz P 2009	Randomized, double-blind, controlled multicentre trial	Ecuador	Oral	Primary knee osteoarthritis (Kellgren-Lawrence grade I-III)	10 g hydrolyzed collagen for once-daily administration, 111 participants	NA	A matching amount of placebo (lactose) for once-daily administration, 96 participants	59	15/192	VAS (100 scale), WOMAC, SF-36 score	Baseline, 3 months, 5 months
Chen CC 2023	Randomized, double-blind, four-arm, pilot study	Taiwan	Oral	Mild to moderate knee osteoarthritis ( Kellgren–Lawrence grade I to III)	Hydrolyzed collagen type II, 38 participants	Essence of chicken + hydrolyzed collagen type II, 37 participants	6.8 g maltodextrin, 0.007 g xanthan gum, and 0.43 g yeast extract, 38 participants	45–75 years	17/96	VAS pain score, WOMAC score, fat-free mass, grip strength, SF-36	WOMAC score at 8, 16, and 24 weeks; VAS pain score at 7 and 14 days; grip strength, FFM at 24 weeks
JX Jiang 2014	Prospective,single-centre,randomized,doulble-blind,placebo-controlled trial	China	Oral	Knee osteoarthritis (Kellgren- Lawrence score of 0-I to III)	Peptan B 2000 of bovine origin,8 g per day for 6 months, 46 paticipants	NA	Maltodextrin,8 g per day for 6 months,48 participants	40–70	0/94	WOMAC and the Lysholm scoring system	3 months,6 months
Trč T 2011	Prospective, multicentre, randomized, parallel, double-blind study	Czech Republic	Oral	Knee osteoarthritis (functional class I, II, or III)	10 g enzymatic hydrolyzed collagen once daily for 90 consecutive day, 47 participants	NA	1.5 g glucosamine sulfate once daily for 90 consecutive day, 46 participants	40 years or older	NA	VAS (100 scale), WOMAC, SF-36 score, self-assessment, the investigator’s overall opinion, and reduction of the use of rescue medication	− 7, 0, 15, 30, 60, and 90 days