Knee instability after injury to the anterior cruciate ligament

Abstract

W e have measured anterior and posterior displacement in 563 normal knees and 487 knees with chronic deficiency of the anterior cruciate ligament (ACL). We performed stress radiography using a simple apparatus which maintained the knee at 20° of flexion while a 9 kg load was applied. There was no significant difference in posterior translation dependent on the condition of the ACL. Measurement of anterior translation in the medial compartment proved to be more reliable than in the lateral compartment for the diagnosis of rupture of the ACL, with better specificity, sensitivity and predictive values. We have classified anterior laxity based on the differential anterior translation of the medial compartment and identified four grades in each of which we can further distinguish four subgrades for laxity of the lateral compartment. Within each of these subgroups, either internal or external rotation may dominate and sometimes there is a major translation of both compartments. Radiological evaluation of displacement of the knee in 20° of flexion provides conclusive evidence of rupture of the ACL. A detailed study of pathological displacement is the basis for a classification of laxity. It is then possible to decide for each type of laxity, the surgical treatment which is specifically adapted to the lesion, and to define a reference value for judging outcome.

Reliability of Navigated Knee Stability Examination

“…3,15,36 Further concepts such as the Computerized Accurate Ligament Tester, Knee Signature System, Knee Instability Tester, roentgen stereophotogrammetric analysis or planar stress radiography, and electromagnetic tracking devices have not been routinely used because of the complexity of design and restricted intraoperative applicability. 7,26 A reliable tool for measuring multiplanar motions preoperatively, intraoperatively, and postoperatively has yet to be validated.…”

Technical note: MRI device for active stress of the knee. The practical approach and preliminary data

“…In all patients, tibiofemoral joint alterations demonstrated by the Knee Loader® prototype in clinically stable patients corresponded with those described in the literature and were therefore considered within normal range [15,18,19].…”

“…Il prototipo Knee Loader® in tutti i casi da noi esaminati ha messo in evidenza modificazioni dei rapporti articolari femoro-tibiali che, in pazienti clinicamente stabili, corrispondevano a quanto già descritto in letteratura e quindi considerate da noi nell'intervallo di normalità [15,18,19].…”

What Really Happens during the Lachman Test?

“…The literature regarding stress radiography shows a wide variation of medial and lateral anterior tibial translation during knee examinations similar to that used in our study. 8,12,14,16,21,30 Some studies show a relative increase in anterior tibial translation in the lateral compared to medial compartment, 14,21,30 whereas others have shown the reverse. 8 In vitro and in vivo studies have suggested that in the normal knee, anterior tibial translation is also associated with internal rotation of the tibia relative to the femur.…”