Jerk Test of Hughston Special Test

What is it used for?

• Diagnosing Anterolateral Rotatory Instability (ALRI) (ACL + Lateral Capsule).
• Similar to the Pivot Shift but performed in reverse (Flexion to Extension).

How to Perform

• Position: Patient supine, hip flexed 45°, knee flexed 90°.
• Action: Apply a Valgus stress and Internal Rotation to the tibia.
• Movement: Slowly extend the knee.

Interpretation of Results

• Positive Test: At ~20-30° of flexion, the tibia (which was subluxated anteriorly) suddenly reduces with a palpable 'jerk' or 'clunk'.

References

• Magee, D. J. (2021). Orthopedic Physical Assessment.