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The ‘ierk’ test


The subject lies upine with the hip flexed to about 45°, and the knee to 90°. The examiner supports the subject’s leg, with one hand at the foot and the other at the knee, the thumb behind the fibular head.


The hand at the foot rotates the tibia slightly internally, while the other hand exerts a mild valgus stress at the knee. The examiner ex.tends the knee gradually, maintaining the internal rotation and valgus stress. A positive result is indicated if, on attaining about 30° of flexion, anterior subluxation of the tibia occurs with a sudden movement, which is called a jerk. The forwards shift can be seen and felt by
the examiner. At the same moment, the subject will recognize the feeling of instability.

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