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Check the deep tendon reflexes using impulses from a reflex hammer to stretch the muscle and tendon. The limbs should be in a relaxed and symmetrical position, since these factors can influence reflex amplitude. As in muscle strength testing, it is important to compare each reflex immediately with its contralateral counterpart so that any asymmetries can be detected. If you cannot elicit a reflex, you can sometimes bring it out by certain reinforcement procedures. For example, have the patient gently contract the muscle being tested by instructing the patient to raise the limb very slightly, or to concentrate on forcefully contracting muscles in a different part of the body just at the moment when the reflex is tested. When reflexes are very brisk, clonus is sometimes seen. Clonus is a repetitive rhythmic contraction of the muscle that occurs in response to muscle and tendon stretch. Deep tendon reflexes are often rated according to the following scale:

• 0: Absent reflex
• 1⁺: Trace, or seen only with reinforcement
• 2⁺: Normal
• 3⁺: Brisk
• 4⁺: Nonsustained clonus (i.e., repetitive vibratory movements)
• 5⁺: Sustained clonus