How do I keep my joints flexible and prevent osteoarthritis?
Stretching keeps joints flexible, but targeted strength training of the surrounding muscles provides the strongest protection. Keep expectations about stretching as an osteoarthritis inhibitor modest: the evidence for that is absent from these studies.
Stretching works for flexibility, but the form you choose matters less than you might expect. Both ordinary static stretching (holding a position) and PNF stretching (in which you alternately contract and relax your muscles) demonstrably improve the range of motion in hips and hamstrings. Which technique is superior remains unclear: only one of the five studies in this research found an advantage for PNF. Practically speaking: do whatever you will stick with consistently.
Tissue flossing is a newer approach in which you wrap an elastic band tightly around a joint while moving it. In a small study of 17 young men, this improved knee mobility more than dynamic stretching did. These are preliminary findings from a single small study, so do not set high expectations based on them.
Preventing joint problems also depends heavily on the muscles surrounding those joints. An eight-week programme targeting the core muscles reduced unfavourable knee loading during jumping and squatting in female basketball players. The study was small (nine participants in the training group), but the principle is consistent: strong core muscles protect the joints above and below them. Even more concrete evidence comes from handball: a targeted exercise programme involving shoulder strength, scapular stabilisation and thoracic spine mobility reduced the risk of shoulder problems by 28% in 660 handball players.
Whether stretching specifically prevents injuries in runners is scientifically contested and has not been conclusively demonstrated. Stretching therefore appears to contribute more to range of motion than to direct injury prevention. The strongest protection for joints seems to come from targeted strength and stability training of the surrounding muscles, not from stretching alone.
Based on a meta-analysis on stretching (PMID 28182516), two small studies on tissue flossing/dynamic stretching (PMID 33239941) and core training (PMID 31386583), an RCT in handball players (PMID 27313171), and a review article on stretching in runners (PMID 20610027). No studies specifically on osteoarthritis pathology or cartilage; the claims concern mobility and joint protection in healthy athletes.