The most common and significant complication associated with fractures or dislocations of the knee is:

The answer for the question is the neurovascular compromise.
Any orthopaedic injury that leads to neurovascular compromise represents a potentially limb-threatening emergency. Insufficient arterial blood flow to a distal extremity can result from either vessel transection or laceration caused by bony fragment.

Gases enter the atmosphere and trap the sun's heat warning the earth.

Enzyme. anything that ends in "ase" is usually an enzyme.