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Pivot Shift Test

- See:
      - Anterior Cruciate Ligament
      - Anterolateral Rotatory Instability
      - Clunk Test
      - Lachman
      - Losee Test
      - Reverse Pivot Shift Test

- Discussion:
    - pivot shift assesses degree of incapacitating dysfunction in knee with ACL deficiency and secondary restraint deficiency;
    - pivot-shift test reproduces event that occurs when knee gives way becuase of loss of ACL;
          - there is a forward subluxation of tibia during sudden change in direction;
    - test may also be used to judge the success of ACL reconstruction;
    - backgroud:
          - w/ an ACL tear, the knee will remain reduced in full extension, will subluxate in 20-30 deg of flexion (w/ appropriate stress),
                 and will then again reduce w/ further flexion;
          - as knee is moved from flexion into extension, shorter, more highly curved lateral condyle exhausts its articular surface & is
                 checked by ACL, whereas larger & less curved medial condyle continues its forward roll and skids backward, assisted by
                 tightening of PCL;
          - flexion of extended knee is preceded by internal rotation of tibia, usually produced by popliteus;
          - this rotation relaxes tension of collateral ligaments sufficiently to permit flexion;
          - as the femur rotates internally, the tibia moves forward, and the lateral femoral condyle impacts the posterior lateral tibial plateau;
          - result is external rotation of tibia that tightens collateral ligaments, and the joint is "screwed home;"
    - grading jakob:
          - I  : Gentle twisting slide with tibia twisting internally maximally;
          - II : Clunk with tibia neutral, negative when tibia externally rotated;
          - III: Painless glide for examiner and patient;
                      - ref: Rotational Knee Instability in ACL-Deficient Knees: Role of the Anterolateral Ligament and Iliotibial Band as Defined by Tibiofemoral Compartment Translations and Rotations.
          - IV : Jamming and Plowing, impingement;

- Exam Technique:
    - various methods of eliciting pivot-shift phenomenon have been described;
    - during test, pt is supine & examiner holds pt's leg w/ both hands; 
    - it is important to abduct the hip to relax the ITB and allow the tibia to rotate;
    - knee is held at approx 20 degrees of flexion and in neutral rotation;
    - patient relaxes his or her muscles, which allows femur to drop backward (if the ACL is torn);
    - knee is then placed in full extension w/ aplication of valgus stress & internal rotation stress;
          - knee extension: posterior capsule holds reduction;
    - slowly flex the knee while valgus and internal rotation is maintained;
          - knee flexion: at 40 deg: iliotibial band provides reduction;
    - load is then placed on knee joint by application of axial or valgus force (or both) while tibia is kept in a neutral rotation;
    - if test is positive, a subluxation (lateral > medial) will occur at 20 to 40 deg of flexion, indicating ACL deficiency;
    - rotation can be added to accentuate or diminish subluxation;
    - isolated tear of the ACL will produce only small subluxation;
          - greater subluxation occurs when the lateral capsular complex or semimembranosus corner is also deficient; 
    - test can also be be performed from flexion to extension;
          - tibia is placed in external rotation and as the knee is extended ensure that the tibia can rotate - allowing subluxation to
                   occur at between 10-20 deg;
    - impingement:
          - w/ compression/axial loading, there is impingement of unsitting lateral femoral tibial articulation;
          - posteriorly displaced lateral femoral condyle joins into posterolateral articular margin of the tibia;
          - exagerated when lateral joint surfaces are squeezed (valgus stress);
          - IT tract provides reduction by passively twisting tibia externally;
          - severe valgus instability may make this test difficult to elicit because of the lack of medial support;
    - extension: posterior capsule holds reduction;
    - flexion: at 40 deg: iliotibial band provides reduction

Injury to the anterior cruciate ligament producing the pivot-shift sign.

The lateral pivot shift: a symptom and sign of anterior cruciate ligament insufficiency.

An analysis of the pivot shift phenomenon. The knee motions and subluxations induced by different examiners.

Relationships Between Objective Assessment of Ligament Stability and Subjective Assessment of Symptoms and Function After Anterior Cruciate Ligament Reconstruction

Implications of the Pivot Shift in the ACL-Deficient Knee.

Relationship Between the Pivot Shift and Lachman Tests: a Cadaver Study

“Anatomic” Single-Bundle Anterior Cruciate Ligament Reconstruction Reduces Both Anterior Translation and Internal Rotation During the Pivot Shift