To compare self-reported osteoarthritis of the knee and hip in adults who ran at least 1 marathon as a child with adults who ran high-school cross country (HSCC). Subject self-recall retrospective survey. Electronic survey. 319 adults who either ran a marathon under age 18 or ran HSCC recruited from running clubs, marathon participants, and on-line interest groups. Survey. Self-reported history of osteoarthritis (OA), joint pain, anterior cruciate ligament injury, still running or running marathons, and number of marathons as an adult. One hundred twenty-three respondents ran a marathon under age 18 (26% female) and were 40 years old (sd 16) and 196 ran HSCC (53% female) and were 36 years old (sd 13). The mean age of first marathon was 15 (sd 2.3, range 5-17); 50% ran 1% and 50% ran >1 marathon. Child marathoners reported a family history of OA in knees or hips (26%) or a joint replacement (30%) compared with 24% and 28% of HSCC runners. 10% of child marathoners and 7% of HSCC reported OA and 24% and 21% reported daily or weekly joint pain. 91% of all respondents are still running; 78% of child marathoners (mean 17, range 1-91) and 80% HSCC ran ≥1 marathons as adults (mean 10, range 1-80). Adults who ran marathons as children compared with adults who ran HSCC self-report similar rates of the knee and hip OA, chose to participate of their own accord, continue to run as adults, played other sports, and did not "specialize" in marathons.