Purpose: To study distractive muscle injuries applying US and MRI specific classifications and to find if any correlation exists between the results and the return to sport (RTS) time. The second purpose is to evaluate which classification has the best prognostic value and if the lesions extension correlates with the RTS time. Methods: A total of 26 male, professional soccer players (age 21.3 ± 5.6), diagnosed with traumatic muscle injury of the lower limbs, received ultrasound and MRI evaluation within 2 days from the trauma. Concordance between US and MRI findings was investigated. The relationships between MRI and US based injury grading scales and RTS time were evaluated. Correlation between injuries’ longitudinal extension and RTS time was also investigated. Results: The correlation between US and MRI measurements returned a Spearman value of r_s = 0.61 (p = .001). Peetrons and Mueller-Wohlfahrt grading scales correlations with RTS time were r = 0.43 (p = .02) and r = 0.83 (p = < .001). The lesion’s extension correlation with RTS time was r = 0.63 (p < .001). The correlation between the site of the lesion and its location with the RTS time were r_s = 0.2 and r_s = 0.25. Conclusions: Both US and MRI can be used as prognostic indicators along with the Peetrons (US) and the Mueller-Wohlfahrt (MRI) classifications. MRI is more precise and generates more reproducible results. The lesion craniocaudal extension must be considered as a prognostic indicator, while the injury location inside the muscle or along its major axis has doubtful significance.

Objective: To describe injury mechanisms and magnetic resonance imaging (MRI) findings in acute rectus femoris (RF) injuries of soccer players using a systematic video analysis. Design: Descriptive case series study of consecutive RF injuries from November 2017 to July 2022. Setting: Two specialized sports medicine hospitals. Participants: Professional male soccer players aged between 18 and 40 years, referred for injury assessment within 7 days after a RF injury, with an available video footage of the injury and a positive finding on an MRI. Independent Variables: Rectus femoris injury mechanisms (specific scoring based on standardized models) in relation to RF muscle injury MRI findings. Main Outcome Measures: Rectus femoris injury mechanism (playing situation, player/opponent behavior, movement, and biomechanics), location of injury in MRI. Results: Twenty videos of RF injuries in 19 professional male soccer players were analyzed. Three different injury mechanisms were seen: kicking (80%), sprinting (10%), and change of direction (10%). Isolated single-tendon injuries were found in 60% of the injuries. Of the kicking injuries, 62.5% included complete tendon ruptures, whereas both running injuries and none of the change of direction injuries were complete ruptures. The direct tendon was involved in 33% of the isolated injuries, and the common tendon was affected in all combined injuries. Conclusions: Rectus femoris injuries typically occur during kicking among football players. Most of the RF injuries involve a complete rupture of at least one tendon. Kicking injuries can also affect the supporting leg, and sprinting can cause a complete tendon rupture, whereas change of direction seems not to lead to complete ruptures.

Introduction: Football was the first sport to resume competitions after the coronavirus disease 2019 (COVID-19) lockdown and promptly the hypothesis was raised of a potential relationship between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and musculoskeletal injuries in athletes. This study aimed to confirm the association between SARS-CoV-2 infection and muscle strain injury in a large population of elite football players and to investigate if the COVID-19 severity level could affect the risk of injury. Methods: A retrospective cohort study involving 15 Italian professional male football teams was performed during the Italian Serie A 2020–2021 season. Injuries and SARS-CoV-2 positivity data were collected by team doctors through an online database. Results: Of the 433 included players, we observed 173 SARS-CoV-2 infections and 332 indirect muscle strains. COVID-19 episodes mostly belonged to severity level I and II. The injury risk significantly increased after a COVID-19 event, by 36% (HR = 1.36, CI_95% 1.05; 1.77, p-value = 0.02). The injury burden demonstrated an 86% increase (ratio = 1.86, CI_95% 1.21; 2.86, p-value = 0.005) in the COVID-19 severity level II/III versus players without a previous SARS-CoV-2 infection, while level I (asymptomatic) patients showed a similar average burden (ratio = 0.92, CI_95% 0.54; 1.58, p-value = 0.77). A significantly higher proportion of muscle–tendon junction injuries (40.6% vs. 27.1%, difference = 13.5%, CI_95% 0.002%; 26.9%, p-value = 0.047) was found when comparing level II/III versus Non-COVID-19. Conclusions: This study confirms the correlation between SARS-CoV-2 infection and indirect muscle injuries and highlights how the severity of the infection would represent an additional risk factor.

Purpose: The aim is to investigate whether contrast medium can improve accuracy in the assessment of healing muscle injury in high-level professional athletes. Materials and methods: Our series is a retrospective study including the records of 22 players (mean age 28 ± 5 SD) with lower limbs muscle injuries type 3a (Mueller-Wohlfarth). All athletes received two MRIs: the day after the injury and before resuming heavy effort activities. Contrast medium uptake was measured in the second MRI by comparing the mean enhancement at the lesion site (ME) with that of the healthy contralateral muscle (HM). The result is a percentage referred to as muscular contrast index (MC index). The difference between the mean MC index value between athletes with and without re-injury was assessed with both the Mann–Whitney and the Kruskal–Wallis test. Results: Twenty-nine muscle injuries matched the inclusion criteria. The mean MC index values, adjusted for the variable of time elapsed between the last contrast examination and return to the field, were significantly different in the two study groups (p < .001). Conclusion: The contrast medium in the follow-up of muscle injuries may be useful in determining the degree of scar stability in a healing injury. Injuries with a high MC index were found to be ‘unstable’, with a higher rate of recurrence than those with a low MC index. Resumption of competitive activity after achieving not only clinical resolution but also a satisfactory MC index value may increase the safety of return to the field and reduce the recurrence rate.