Abstract
Purpose: The aim of this paper is to draw delegates’ attention to the published evidence that exists about these injuries and to challenge the concept that these laxities can be ignored, especially when associated with injuries to the ACL and PCL.
Background: The common impression that injuries to the PLC occur infrequently, require major force and are best treated by early repair, is true for Grade III injuries. Grade II injuries are more common, more difficult to detect clinically and may develop insidiously.
Even enhanced MR imaging cannot reliably assess grade II injuries to the PLC. This can result in patients with lack of trust in the knee, pain on kneeling, difficulty with twisting, slopes and rough ground, being reassured by their surgeon that their knee is stable, when both know that this is not the case.
Failure to detect a Grade II injury to the PLC in association with an ACL or PCL tear may result in ongoing subtle symptoms of instability, overloading and possible failure of a cruciate reconstruction.
Methods: A careful literature review was carried out with particular emphasis on the biomechanical studies which provide the scientific basis on which the common clinical tests are based.
Results:
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Significant damage to the popliteus mechanism is required to produce a clinically detectable increase in ER.
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Grade II lesions of the PLC may fail to reach that threshold.
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Of the traditional tests, only the Dial test and electronic Goniometer test can be easily used towards extension. The former is not very sensitive, the latter is time consuming.
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Increased posterior tibial translation (PTT) is a more reliable assessment of Grade II lesions and biomechanical studies support the prominent role of the posterolateral corner at 20° of knee flexion
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Only two obscure clinical tests and the unpublished posterior Lachman test assess PTT below 30° of knee flexion
Conclusion: Until surgeons specifically test for increased PTT at 10–20° of knee flexion, Grade II lesions of the PLC will largely go unrecognised.
Correspondence should be addressed to: Tim Wilton, BASK, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
