Physical examination maneuver

Physical Exam

Patellar Deep Tendon Reflex

also known as Knee jerk
🎬
Video coming September 2026

How to Perform

With the knee flexed and the leg hanging freely (or, in a bedbound patient, supported behind the knee in slight flexion), strike the patellar tendon just below the kneecap with the reflex hammer. The normal response is reflex extension of the lower leg.

How to Interpret

Showing 4 of 9 findings

L3-L4 Radiculopathy

Hyporeflexia (≤1+) at patella
Rule in
Somewhat helpful
Rule out
—
Evidence:Limited

Peripheral Neuropathy

Multi-level hyporeflexia pattern (Achilles, patellar, and biceps reflexes all impaired)
Rule in
Very helpful
Rule out
Minimally helpful
Evidence:Limited
Lower-extremity hyporeflexia pattern (Achilles + patellar both impaired)
Rule in
Somewhat helpful
Rule out
Somewhat helpful
Evidence:Limited

Upper Motor Neuron Lesion

Hyperreflexia (≥3+) at patella
Rule in
Helpful
Rule out
Somewhat helpful
Evidence:Limited

References

  • Iversen T, et al. BMC Musculoskelet Disord. 2013;14:206. PMID: 23837886.
  • Li ZF, Niu XL, Nie LL, Chen LP, Cao CF, Guo L. Diagnostic value of clinical deep tendon reflexes in diabetic peripheral neuropathy. Arch Med Sci 2023;19(5):1201-1206. doi:10.5114/aoms.2020.100656. PMID 37732044. PMC10507750.
  • Teitelbaum JS, Eliasziw M, Garner M. Tests of motor function in patients suspected of having mild unilateral cerebral lesions. Can J Neurol Sci. 2002 Nov;29(4):337-344. doi:10.1017/S0317167100002201. PMID: 12463489.
  • Erb WH. Über Sehnenreflexe bei Gesunden und bei Rückenmarkskranken. Arch Psychiatr Nervenkr. 1875;5:792-802.

Related Systems / Regions

Lower ExtremitiesNeurological

Related Bedside Tests

🎬Video coming Sept 2026
Achilles Deep Tendon Reflex
aka Ankle jerk
Rule in:VHPeripheral Neuropathy, HUpper Motor Neuron Lesion, SHHypothyroidism +5 more
Rule out:VHPeripheral Neuropathy, SHUpper Motor Neuron Lesion, NHS1 Radiculopathy +4 more
🎬Video coming Sept 2026
Biceps Deep Tendon Reflex
aka Biceps jerk
Rule in:VHPeripheral Neuropathy, HUpper Motor Neuron Lesion, SHC5-C6 Radiculopathy +3 more
Rule out:SHUpper Motor Neuron Lesion, MHPeripheral Neuropathy, IEC5 Myelopathy +1 more
🎬Video coming Sept 2026
Babinski Reflex
aka Plantar reflex
Rule in:VHUpper Motor Neuron Lesion, IEMotor Neuron Disease (ALS), IEMultiple Sclerosis +2 more
Rule out:SHUpper Motor Neuron Lesion, IEMotor Neuron Disease (ALS), IEMultiple Sclerosis +2 more
🎬Video coming Sept 2026
Head and Face Inspection
Rule in:HAcromegaly, HAcute Stroke, IECushing Syndrome +1 more
Rule out:SHAcromegaly, SHAcute Stroke, SHHypothyroidism +2 more
🎬Video coming Sept 2026
Heart Rate
Rule in:HAtrial Fibrillation, SHHypothyroidism, SHPneumonia +7 more
Rule out:VHAtrial Fibrillation, MHAdverse Short-term Outcome in Confirmed Pulmonary Embolism, IECardiac Tamponade +5 more
🎬Video coming Sept 2026
Pronator Drift
Rule in:VHBrain Tumor, HStroke, NHUpper Motor Neuron Lesion +1 more
Rule out:VHStroke, MHBrain Tumor, NHUpper Motor Neuron Lesion +1 more