Introduction Musculoskeletal (MSK) injuries in US trail sports are understudied as trail sport popularity grows. This study describes MSK injury patterns among hikers, trail runners, and mountain bikers from 2002 through 2021 and investigates MSK injury trends acquired during mountain sports. Methods The National Electronic Injury Surveillance System (NEISS) was used to identify US emergency department (ED) patients from 2002-2021 (inclusive) who endured MSK injuries during hiking, trail running, or mountain biking. Injury rates and national estimates were calculated across demographics. Results 9835 injuries were included (48.4% male, 51.6% female). Injuries increased over time, with 1213 from 2002-2005 versus 2417 from 2018-2021. No sex differences existed before 2010, after which female injury rates exceeded those of males. The following findings were statistically significant, with P<0.05: females endured more fractures and strains/sprains; males endured more lacerations; concussions and head injuries were higher among those <18 y; dislocations and strains/sprains were higher for 18 to 65 y; fractures were higher for >65 y; <18 y had high mountain-biking and low running rates; 18 to 65 y had high running rates; and >65 y had low biking and running rates. Although all diagnoses increased in number over time, no significant differences existed in the proportion of any given diagnosis relative to total injuries. Conclusions MSK injuries during trail sports have increased since 2002. Males endured more injuries until 2009, after which females endured more. Significant sex and age differences were found regarding injury diagnosis and body parts. Further studies are needed to confirm these trends and their causes.