I think that any injury is serious. My suggestion is to see a good doctor, perferably a sports doctor, about your injury. A serious injury will likely mean that you should not do the marathon...
Most likely your knee problem is caused by worn or wrong shoes, running on non-level streets... on knee injuries that will give you some introductory info plus other links.
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Stem Cells for Brain Injury Recovery?by
Kim S.
By Kent Heckenlively, Esq. Learning disabilities and neural defects which result in behavior problems have been notoriously difficult to treat, since the substance that causes the abnormalities...
Stem Cell Research with Neural Injuryby
imicsome
for the purpose of repairing damage to the nervous system caused by disease, such as multiple sclerosis, or injury... are being learned about stem cells and exactly how they can help people with a wide variety of illnesses, injury...
Does Mild Traumatic Brain InjuryCause Cognitive Problems?by
Dr. Romeo V.
brain injury were followed up over six months post-admission. In addition to a battery... (especially fatigue) but not to actual extent of injury. Severity of self-reported cognitive complaints was found not...