Everyone by now has heard that Joe Mauer has been placed on the 15-day DL due to "bilateral leg weakness." What not everyone knows is what that exactly means and how serious it can be.

Bilateral leg weakness is muscle weakness in both legs. Symptoms can include weakness, fatigue, muscle aches, fever, muscle pain, leg pain, and tingling or numbness in the legs. The condition is neurological, not musculoskeletal. That is, it has nothing to do with Mauer's recent arthroscopic knee surgery.

The key to treating bilateral leg weakness is determining the underlying cause. It's often an indicator of something else, and can be brought on by a number of conditions. It could be a viral infection or the by-product of a bout with influenza. It can be caused by a tick bite or West Nile Virus. In rare cases it can be a sign of multiple sclerosis, multiple myeloma, or even ALS (Lou Gehrig's Disease).

Mauer will be seeing a specialist—the same doctor he saw for sacroiliac joint inflammation in 2009—in Baltimore tomorrow, where he hopes he can find out why this is happening and how to treat it. Hopefully it isn't anything too serious and all he needs is some rest and a little physical therapy.

UPDATE: Mauer was admitted to a Tampa hospital late last night with flu-like symptoms and stomach pains. He was discharged between 3:30 and 4:00 this morning. As a result, Mauer's scheduled exam in Baltimore has been postponed. It's starting to sound like the bilateral leg weakness is nothing too serious but a more thorough exam will hopefully answer a lot of questions.