The biceps reflex is a stretch reflex in which a tap on the biceps tendon makes the biceps contract and the elbow bend slightly. It tests the C5 and C6 roots and the musculocutaneous nerve. It is one of the standard tendon reflexes of the arm.
| Nerve root | C5-C6 |
|---|---|
| Area | Biceps tendon in the antecubital fossa (front of the elbow) |
| How to test | With the elbow relaxed and partly bent, the examiner places a thumb on the biceps tendon and strikes the thumb with a reflex hammer, watching and feeling for biceps contraction. |
| Muscles | |
| Nerve Supply | Musculocutaneous nerve |
Shows that the sensory and motor nerve loop through C5-C6 is intact and that descending control of the reflex is normal.
A reduced biceps reflex on one side suggests C5 or C6 radiculopathy or a musculocutaneous nerve lesion. A brisk reflex points to an upper motor neuron lesion above C5, such as cervical myelopathy. Tendon reflexes are graded 0 (absent) to 4+ (clonus), with 2+ normal; symmetry matters more than the absolute grade.
Root compression at C4-C5 or C5-C6 reduces the biceps reflex on the affected side, often with arm pain and weakness.
Damage above the reflex arc, such as cervical myelopathy, stroke or multiple sclerosis, removes inhibition and makes the reflex brisk, sometimes with spread to nearby muscles.
Generalised nerve damage, for example from diabetes, reduces or abolishes tendon reflexes, starting with the ankle reflexes.
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