- 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.
Implications of the Pivot Shift in the ACL-Deficient Knee.
Relationship Between the Pivot Shift and Lachman Tests: a Cadaver Study