Tendons connect muscles to bones — until they don’t. When the tendon tears away from the bone, that’s an “avulsion.” Not a subtle injury! Especially if the muscle is big, you wouldn’t think that an avulsion would be hard to diagnose, but it can be. According to O’Laughlin et al, hamstring avulsions “can be difficult to diagnose due to swelling and patient guarding, which may mask a visibly palpable defect and lead to delays in diagnosis.”
In that case study, the only diagnosis was “hamstring pain” for several days, before the avulsion was finally confirmed by MRI, and surgically repaired. It’s not hard to imagine cases where the diagnosis would have taken much longer.
This is a good example of imaging at its most clinically useful. Premature, excessive, and misleading imaging are all huge problems (especially in musculoskeletal medicine), but sometimes looking inside tissues is exactly what you need to get to “well, there’s your problem!”