Rectus femoris scarring as a marker of greater muscle injury risk in young football players: a prospective observational study.

The objective of the present study was to assess whether the presence and characteristics of ultrasound-detected rectus femoris (RF) scars were associated with a greater risk of subsequent muscle injuries. In this prospective cohort study conducted over two consecutive competitive seasons in a professional football Club, all available players from the male Under-15 to Under-19 and Second Team underwent standardized ultrasound screening at the beginning of each competitive season. Scar presence, laterality, number, size and involvement of tendons or aponeuroses (MT scars) were recorded, along with a detailed injury history. Players were prospectively followed and time-loss muscle injuries were systematically recorded. A total of 176 players were included, accounting for 262 player-seasons; in 62 (24%) at least 1 RF scar was present. Players with scars showed higher muscle injury incidence compared with scar-free players (p < 0.01). Among players with RF scars, those with MT involvement showed a higher injury incidence (p = 0.047). When adjusting for age and previous injury, the association between the presence of RF scars and increased injury incidence was substantially reduced (p = 0.35). This association was also attenuated for MT scars (p = 0.08), which conversely showed an association with a shorter time to first injury (p = 0.02). In conclusion, the presence of RF scars was associated with a higher overall incidence of muscle injuries, but not after adjustment for age and previous injury. The presence of MT scars identified a subgroup of players in which this association was particularly marked. This finding should be considered exploratory and warrants further investigation in future studies.