Upgoing plantar reflex: This is an early finding suggestive of complete spinal cord injury, as it indicates an upper motor neuron lesion. The upgoing plantar reflex, also known as the Babinski sign, is a classic indicator of upper motor neuron damage, which is consistent with a complete spinal cord injury.

Clonus: Clonus is a sign of upper motor neuron damage, which can be seen in complete spinal cord injuries. It is characterized by rhythmic, involuntary muscle contractions and relaxations.
Priapism: Priapism, or a prolonged erection, can be an early finding in complete spinal cord injuries, particularly in the acute phase. This is due to the disruption of normal autonomic control over erectile function.
Hyperreflexia: Hyperreflexia, or exaggerated reflexes, can occur after a complete spinal cord injury, although it may take some time to develop. Initially, there may be a period of spinal shock with decreased reflexes, but as the condition evolves, hyperreflexia can become a prominent feature.

Spinal shock: While not a specific physical finding like the others, recognizing spinal shock is crucial. It is a condition that immediately follows a spinal cord injury and can lead to hypotension, bradycardia, and decreased peripheral resistance, potentially leading to organ hypoperfusion and failure if not promptly addressed.

Other less common signs of spinal cord injury: These might include changes in bowel or bladder function, sensory deficits, or other autonomic dysfunctions. While important, these are either less specific or may not be as immediately apparent in the early stages post-injury.