Can knee injury w/o swelling cause pain/discomfort in the calf or achilles? does a mri detect every possible knee injury or is more imaging required?

Yes: Knee problems can refer pain into the calf--MRI is probably the best imaging technique available

MRI not great: MRI can miss many things- best way to diagnose an Orthopedic conditions is with a good history and exam by a good fellowship trained Ortho specialist who focuses their practice on the bandy part you have concerns about (e.g knee doc)