Joint magnetic resonance imaging: normal variants and pitfalls related to sports injury.

MR imaging abnormalities, such as increased signal within normally hypointense structures, form and attachment abnormalities, fluid collections in joints, tendon sheaths and bursa, or even tumors, such as Morton's neuromas, are common in asymptomatic volunteers. They may be explained by normal physiology, anatomic variability, MR imaging artifacts, or true abnormalities without clinical importance. Although it is not always possible to differentiate such variants or artifacts from clinically relevant findings, it is important to know their potential cause and clinical importance and not to over-report them as abnormality requiring additional imaging or treatment. Thorough knowledge of normal anatomy is crucial in this situation.