assesses degree of incapacitating dysfunction in knee with anterior crucitate ligament (ACL) deficiency and secondary restraint deficiency
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
various methods of eliciting pivot-shift phenomenon have been described
during test, patient is supine and examiner holds patient's leg with both hands
is important to abduct the hip to relax the IT band 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 with aplication of valgus stress and internal rotation stress;
knee extension: posterior capsule holds reduction
slowly flex the knee while valgus and internal rotation is maintained;
knee flexion: at 40 degrees: 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 degrees
this is a difficult test because meniscal involvement, such as with bucket handle tears of the medial meniscus, may limit range of motion and muscle guarding to produce a false-negative
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