Causes of absent tendon reflexes:

Tendon reflex may be absent in the following situations

• Lower motor neurone disease
• Neuronal shock
• Marked spasticity and muscle contracture
• Normal individuals unable to relax

It is  seen in lower motor neuron lesions involving  any part of the reflex arc

• Lesion of the sensory nerve (polyneuritis)
• Lesion of the sensory root (tabes dorsalis)
• Lesion of the anterior horn cell (poliomyelitis)
• Lesion of the anterior root (compression)
• Lesion of the peripheral motor nerve (trauma, polyneuritis).

Before labelling as absent reflex do reinforcement
Reinforcement