Final answer:
Pain that increases with passive movement is the clinical finding that indicates compartment syndrome in a patient with a short leg cast, as it is a specific symptom of the condition caused by increased pressure within the muscle compartments.
Step-by-step explanation:
The nurse should identify pain that increases with passive movement as a manifestation of compartment syndrome in a client with a short leg cast. Compartment syndrome is a condition that occurs when there's increased pressure within a confined body space, especially within the muscle compartments of the limbs, which can compromise circulation and nerve function. This can be due to swelling after trauma or cast application. The key symptoms of compartment syndrome include intense pain more severe than expected from the injury itself, and this pain is exacerbated by stretching the muscle group within the compartment (passive movement), a sensation of tightness or pressure in the affected limb, paresthesia (pins and needles), weakness, and pallor. Unlike areas of warmth on the cast, a bounding pedal pulse, or a capillary refill less than 2 seconds, which do not necessarily indicate compartment syndrome, increased pain with passive movement is a more specific finding for this condition.