The Knee Jerk /Patellar Reflex : Grading of Reflexes , learn with demonstration on the patients (#MadeEasy)
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#coticospinaltractdisorders
how to perform knee jerk reflex on a patient?
muscles involved in this knee reflex?
It is a deep tendon reflex.
The patellar reflex is contraction of the quadriceps femoris muscle, with resulting extension of the knee, in response to percussion of the patellar tendon.
A firm tap on the tendon draws the patella down, stretching the quadriceps an provoking reflex contraction.
There is a latency of around 18ms between stretch on the patellar tendon and the beginning of contraction of the quadriceps femoris muscle.

Root Value of the knee reflex :
Femoral nerve (L2-L4)
The #quadriceps muscle is composed of four muscles :

I.Rectus femoris
II.Vastus lateralis
III.Vastus medialis
IV.Vastus intermedius
Grading:
0 = Absent
1+ = Present but diminished
2+ = Normal
3+ = Increased but not necessarily pathological
4+ = Markedly hyperactive/ pathological/sometimes accompanied by sustained clonus
Significance:
Hyperactive reflexes is seen in UMN lesions i.e corticospinal tract disorders.
Hypoactive reflex is seen in LMN lesions i.e in neuropathy, spinal cord disorders.