One hundred eleven acute muscle injuries in 110 patients (85% male) were assessed. Injured muscle groups included 85 thigh injuries (44 hamstring, 41 non-hamstring), 19 lower leg injuries, and 7 injuries in other locations (see Table 1 for patients`characteristics). Example cases can be seen in Figures 6-11.

Table 1: Patients`characteristics, SD= standard deviation

Fig 8: 21-year-old male, acute injury of medial gastrocnemius head after a sprint (BAMIC: 3b; Munich: indirect_3B; Chan: II_2_B_e). Coronal STIR sequence shows large edema (arrows, length: 24 cm) in the medial gastrocnemius muscle.

Fig 9: 21-year-old male (same patient as in Fig. 8), acute injury of medial gastrocnemius head after a sprint (BAMIC: 3b; Munich: indirect_3B; Chan: II_2_B_e). Transverse PDfs reveals edema intramuscular (arrows; in more than 50% of the cross sectional area) and in myofascial/perifascial location. Fluid is seen between the medial gastrocnemius and soleus muscle. This injury is also known as "tennis leg"

Kappa values (95% confidence interval) were as follows: 0.506 (0.499, 0.514) for BAMIC, 0.566 (0.549, 0.584) for the Munich Consensus Injury Classification, and 0.306 (0.302, 0.311) for the Chan et al. Classification. The highest reproducibility was observed for hamstring injuries using the Munich Consensus Injury Classification (0.587, 0.560, 0.613), while the lowest was for lower leg injuries using the Chan et al. Classification (0.199, 0.185, 0.213). For detailed results see Tables 2 and 3.

Table 2: Interreader reliability: kappa values (95% conficence interval) are shown.

Table 3: Interreader reliability: kappa values (95% confidence interval) are shown.

Most injuries were classified as Grade 2b (n = 31, 27.9%) in the BAMIC classification. In the Munich Consensus Injury Classification, indirect muscle injuries Grade 3B (n = 52, 46.8%) were the most frequently assigned category.

Using the Chan et al. Classification, the most frequently assigned ratings were severity Grade II (n = 76, 68.5%) and location in the muscle center (type 2, not at the myotendinous junction). Among type 2 lesions, injuries were most commonly observed in the middle and distal part of the muscle, specifically in the intramuscular location 1 types B (25.2%) and C (20.7%). For intramuscular location 2, edema in the myotendinous zone (19.8%) was most often seen.

Fig 10: 24-year-old male, soccer player, acute injury of left biceps femoris muscle (BAMIC: 4c; Munich: indirect_4; Chan: III_2_A_e (combined: myofascial and myotendinous)

Fig 11: 24-year-old male (same patient as in Fig. 10), acute injury of right adductor longus muscle (asterisk; (BAMIC: 2a; Munich: indirect_3A; Chan_II_2_B_c). Transverse PDFs shows edema in myofascial/perifascial distribution (arrows; about 25% of cross sectional area) and also edema surrounding the superficial femoral artery/vein (arrowhead).