Pivot Shift


Definition/Description

The pivot shift is a dynamic but passive test of knee stability, carried out by the examiner without any activity of the patient. It shows a dysregulation between rolling and gliding in the kneejoint. The patient lies in supine. The movement is a combination of axial load and valgus force, applied by the examiner, during a knee flexion from an extended position. When the test is positive, it indicates an injury of the anterior cruciate ligament. [1](A2)[2](B)

Clinically Relevant Anatomy
anatomical structure of the knee joint, fig 1

The kneejoint or articulatio genus is the biggest and most complicated synovial joint in the human body. It’s formed by the distal end of the femur and the proximal end of the tibia. Between these two, the medial and lateral meniscus are located. The anterior part of the femur (facies patellaris femoris) articulates with the patella which forms the patellofemoral joint. The cruciate ligaments, situated in the intercondylair space, and the collateral ligaments are important ligaments in the knee.
The anterior cruciate ligament (ACL) joins the area intercondylaris anterior with the medial aspect of the lateral condyle. This ligament extends upwards, dorsally and laterally from the tibial plateau. It prevents the tibia from moving ventrally.
The posterior cruciate ligament (PCL) joins the area intercondylaris posterior with the lateral apect of the medial femurcondyle. The ligament runs medially, straight up and slightly forward. The PCL prevents posterior instability in the knee joint, this means that the tibia doesn’t displace to posteriorly. (Fig 1) [3]
The PCL is stronger than the ACL. Both cruciate ligaments run in a torsion. They stabilize the knee in the sagittal plane. When the knee is in endorotation, the cruciate ligaments are strongly crossed. When in exorotation, they run more parallel. The cruciate ligaments are primarily located in the posterior part of the joint capsule, so the flexion and extension aren’t hampered.[4][5]

Purpose

The purpose of this test is to detect anterolateral rotary instability of the knee. The structures that could be compromised if this test is positive are the ACL, LCL, posterolateral capsule, arcuate complex and ITB.

Technique

The patient lies supine with legs relaxed. The examiner grasps the heel of the involved leg with examiners opposite hand placed laterally on the proximal tibia just distal to the knee. The examiner then applies a valgus stress and an axial load while internally rotating the tibia as the knee is moved into flexion from a fully extended position. [6] A positive test is indicated by subluxation of the tibia while the femur rotates externally followed by a reduction of the tibia at 30-40 degrees of flexion.

[7]

Key Research

Is the pivot shift test a reliable test?
The Pivot Shift test attempts to reproduce the rotary and transalatory instability in an ACL deficient knee. [8] The test has a sensitivity from 0.18 to 0.48 and a specificity from 0.97 to 0.99 for diagnosing an ACL tear. The mean sensitivity and specificity are respectively 0.32 and 0.98. [9] (A1) [10] (A1) [11] (A1) [12] (A1) [13] (A1) Although the test is clinically relevant and reproduces a functional movement of the knee joint, it is difficult to quantify. Recently a study was done using a navigation system to quantify measurements of knee laxity in individuals who underwent ACL reconstruction. The Pivot shift test was reliable with both patient self-assessment of laxity and with surgical performance. [14] This highlights the clinical relevance of the test. Traditionally, the Lachman or the less significant Anterior drawer test were used more often to measure knee laxity due to its quantifiability, however recent advances in technology have allowed for more objective and measurable observations of the motions involved in the pivot shift and may lead to the ability to make the test quanitifiable for research. [15]

(For more information about the accuracy of certain test, in case of an acute knee injury, such as the pivot shift and the lachman test: http://www.aafp.org/afp/2005/0315/p1169.html#afp20050315p1169-t1)

Grading the pivot shift  [2] [16]

“A number of variations of the basic pivot shift test also have been described (Hugston et al. 1976; Slocum et al. 1976; Losee, Johnson and Southwick 1978; Galaway and MacIntosh 1980). All these variations indicate anterior translation and rotational subluxation of the tibia on the femur.” [2]

For the pivot shift test, the examiner applies with one hand an axial and valgus load. This hand is also going to control the rotational position of the tibia during the test. With the other hand, the foot is held firmly against the examiner.
The test can be carried out in three positions of rotation: medial, neutral and lateral rotation of the tibia. (Figs 1,2,3) [2]

figs 1, 2, 3 To show the position of the leg when performing the pivot shift test with endorotation, neutral and exorotation of the tibia.
The results of the pivot shift test are different according to the rotation.
  • Grade I pivot shift: When the tibia is held in maximal medial rotation, there is an abnormal movement that can be felt as a small and gentle sliding reduction. This does not occur in neutral or lateral rotation. A comment here is that it’s barely palpable when the patient is awake but more obvious when he’s under general anaesthesia. A grade I knee is the result of residual laxity or partial cruciate injury. The result is an instability wich is mainly anterolateral.
  • Grade II pivot shift: There is a definite ‘clunk’ when the tibia is in the medially rotated position and there is an abnormal movement in the neutral position. The test is negative when the tibia is held in a position of definite lateral rotation. Because of the clunk and the abnormal movement in neutral position, the difference between grade I and grade II can be detected. In a grade II knee is a more obvious anterior instability, due to a non- functioning ACL. This grade of pivot shift is seen after a fresh ‘isolated’ rupture of the anterior cruciate restraints and in chronic instability of moderate degree.
  • Grade III pivot shift: When the tibia is held in neutral or moderate lateral rotation, an abnormal movement with a pronounced clunk takes place. The tibia can follow its path to maximal anterior laxity. Due to gravity, the femur falls posteriorly and the tibia is located in an anteriorly translated position with a lateral rotation. With a medial rotation the shift is less obvious. With an acute injured knee with moderate to severe damage of the posteromedial and posterolateral structures, including a complete anterior cruciate rupture, we find a grade III pivot shift. This is also the case when the knee has a severe chronic instability and consequent stretching of the secondary posterior restraints.

Table 1. shows the displacement of the medial and lateral plateau of the knee, comparing different grades of severity of an injured knee in accordance with the pivot shift test.

Pivot shift Normal knee Grade I Grade II Grade III
Medial plateau 3mm 5mm 10mm 15mm
Lateral plateau 5mm 12mm 18mm 22mm

Remark: the lateral side of the tibiaplateau is always the most mobile.                                               Table 1 [2](B)

The advantage of repeating the test in different positions of rotation is that it gives a more accurate and reproducible way to quantify the test, unlike the subjective estimation of severity.
But the downside of this method is that it is not completely objective because the examiner must decide whether or not there is a positive pivot shift test. Except for grade III, there is an important positive difference in accuracy of the test when the estimation is done under anaesthesia. Even under anaesthesia it may be difficult to differentiate grades II and III. Such cases should be treated as grade II.
The anterior cruciate ligament is already non-functional from grade II. The difference between grade II and III is that when you have got a grade III, there is additional laxity on both medial and lateral sides. This involves secondary limitation in the posteromedial and posterolateral corners togheter with the purely lateral and medial structures.
Certain types of acute injury may prove difficult to grade and other evidence of complete rupture of the anterior cruciate ligament is needed. The lachman test can give a clear grading and will show that the tibial plateau is subluxating. (see table 2 for more information)
The Lachman test can be executed on a painful knee. This is not the case for the pivot shift test.

Table 2. Shows the subluxation of the knee, comparing different grades of severity of an injured knee in accordance with the Lachman test

Lachman Grade I Grade II Grade III

9mm 10-15mm >15mm

                                                                                                                                                     Table 2 [2](B)

Clinical Bottom Line

The meaning of the test, in determing the clinical significance, is that the different grades of the test can define the level and direction of the laxity, which have been called anteromedial, anterolateral and posterolateral. This results in a visualisation of the progression in chronic anterior cruciate injury. This is due to the successive use of the three positions of the tibial rotation. [2][16]

References

  1. Musahl V., Citak M., O’Loughlin PF., Choi D., Bedi A., Pearle AD. The effect of medial versus lateral menisectomy on the stability of the anterior cruciate ligament-deficient knee. Am J Sports Med 2010;38(8):1591-7. http://www.ncbi.nlm.nih.gov/pubmed/20530720?dopt=AbstractPlus full text: http://ajs.sagepub.com.ezproxy.vub.ac.be:2048/content/38/8/1591.full.pdf+htmlfckLR(accessed 19 Nov 2010). Level of evidence: A2
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Jakob RP., Staubli HU., Deland JT. Grading the pivot shift, objective tests with implications for treatment. VOL 69-B, No.2 1987. http://web.jbjs.org.uk/cgi/reprint/69-B/2/294.pdf (accessed 16 Nov 2010). Level of evidence: B
  3. http://www.taosortho.com/patientinfo/Medical/knees/ACL.htm (figure 1)
  4. Schünke M., Schulte E., Schumacher U., Voll M., Wesker K., Anatomische atlas Prometheus, Algemene anatomie en bewegingsapparaat. Onderste extemiteit: Botten, banden en gewrichten. Houten, 2008.p394, 396.
  5. Kapandji IA. Bewegingsleer, de onderste extremiteit deel 2. De functie van de kruisbanden. Houten, 2009. p135.
  6. Baxter R. Pocket guide to musculoskeletal assessment, second edition. Elsevier Science 2003.
  7. Physiotutors. The Lateral Pivot-Shift Test for Anterior Cruciate Ligament Rupture. Available from: https://www.youtube.com/watch?v=qqy5IfkEvfw
  8. Lane CG, Warren R, Pearl AD. The pivot shift. J Am Acad Orthop Surg. 2008 Dec;16(12):679-88.
  9. Scholten RJPM, Opstelten W, van der Plas CG, Bijl D, Deville WLJM, Bouter LM (2003)fckLRAccuracy of physical diagnostic tests for assessing ruptures of the anterior cruciate ligament:fckLRa meta-analysis. J Fam Pract 52:689-94 http://www.ncbi.nlm.nih.gov/pubmed/12967539 fckLR full text: http://web.ebscohost.com.ezproxy.vub.ac.be:2048/ehost/pdfviewer/pdfviewer?hid=18&sid=25c1a906-13aa-4c59-ba43-a64e200c3c12%40sessionmgr13&vid=2 (accessed 18 Nov 2010. Level of evidence: A1
  10. Briggs KK, Lysholm J, Tegner Y, Rodkey WG, Kocher MS, Steadman JR (2009) ThefckLRreliability, validity, and responsiveness of the Lysholm score and Tegner activity scale forfckLRanterior cruciate ligament injuries of the knee: 25 years later. The American journal of sportsfckLRmedicine 37:890-897 http://ajs.sagepub.com.ezproxy.vub.ac.be:2048/content/37/5/890.full.pdf+html (accessed 18 Nov 2010). Level of evidence: A1
  11. Prins M. The lachman test is the most sensitive and the pivot shift the most specific test for the diagnosis of ACL rupture. Fysiotherapeuten nr 8, 2006. http://www.fysioterapeuten.no/xp/pub/mx/filer/0806_Cap.pdf (accessed 17 Nov 2010). Level of evidence: A1
  12. Van der Plas CG., Opstelten W., Devillé WLJM., et al. Fysische diagnostiek - de waarde van enkele gebruikelijke tests voor het aantonen van een voorstekruisbandruptuur: meta-analyse. Ned Tijdschr Geneeskd. 2005;149:83-8. http://www.ntvg.nl/publicatie/fysische-diagnostiek-de-waarde-van-enkele-gebruikelijke-tests-voor-het-aantonen-van-een-v/volledig (accessed 16 Nov 2010) Level of evidence: A1
  13. Ostrowski JA. Accuracy of 3 Diagnostic Tests for Anterior Cruciate Ligament Tears.J Athl Train 2006; 41(1): 120–121. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1421494/ (accessed 16 Nov 2010) Level of evidence: A1
  14. Lopomo N, Zaffagnini N, Bignozzi S, Visani A, Marcacci M. Pivot Shift Test: Analysis and Quantification of Knee Laxity Parameters using a Navigaion System. J Orthop Res. 2009 July 29.
  15. Katz JW, Fingeroth RJ. The Diagnostic Accuracy of Ruptures of the Anterior Cruciate Ligament comparing the Lachman Test, the Anterior Drawer Sign, and the Pivot Shift Test in Acute and Chronic Knee Injuries. Am J Sports Med. 1986 Jan-Feb;14(1): 88-91.
  16. 16.0 16.1 Heijboer MP. Indicatie, fysische diagnostiek van de knie. Chronische knieklachten. Universiteit van Utrecht 2004. p5 and 7 (http://www.scopie.info/files/Website-elementen/kniecursus2004.pdf (accessed 20 Nov 2010)