Twisting the knee is a common cause of overstretched or torn ligaments of the knee. The knee may give out suddenly when the ACL is torn and there may be a popping sound upon injury. Symptoms of a torn ACL include knee pain, swelling, stiffness, and bruising.
Early symptoms of carbon monoxide poisoning such as headaches, nausea, and fatigue, are often mistaken for the flu because the deadly gas goes undetected in a home. Prolonged exposure can lead to brain damage and even death.
If the symptoms go away in the fresh air you could be feeling the effects of a gas leak or carbon monoxide poisoning. There can also be some clear signs from your household appliances that can indicate a leak, even if you can't smell gas: Always look for a crisp blue flame, rather than an orange or yellow flame.