A study published in the American Journal of Sports Medicine in 2014 consisting of a systematic review of 13 randomized controlled trials evaluated the effectiveness of 12 different agents in preserving articular cartilage of the knee and delaying the progression of osteoarthritis. Treatment with chondroitin sulfate showed a significant reduction in cartilage loss in three of four studies identified compared with placebo.
References:
Gallagher B, Tjoumakaris FP, Harwood MI, Good RP, Ciccotti MG, Freedman KB. Chondroprotection and the prevention of osteoarthritis progression of the knee: a systematic review of treatment agents. Am J Sports Med. 2015 Mar;43(3):734-44. doi: 10.1177/0363546514533777. Epub 2014 May 27. PMID: 24866892. https://pubmed.ncbi.nlm.nih.gov/24866892/