Perhaps you have had a doctor use a reflex hammer to tap the tendon just below your kneecap.
نَتِيجَةَ هذِهِ ٱلضَّرْبَةِ تَسْتَقِيمُ رِجْلُكَ بِشَكْلٍ تِلْقَائِيٍّ وَمُفَاجِئٍ دُونَ أَنْ تُفَكِّرَ فِي ٱلْأَمْرِ .‏