DIAGNOSIS OF KNEE INSTABILITY USING SONOGRAPHY

Objective. A sonographic method has been developed to diagnose knee jo int instabilities and to gain exactly quantifiable and reproducible me asurements. Design. Based on biomechanical considerations, a new posit ioning device to analyse knee instabilities sonographically has been d eveloped and tested in in vivo studies. Background. Common instrumenta l testing techniques are difficult to reproduce and show a lack of rel iability. Method. Using sonography the cortical line of the femur and tibia are observed. At the same time a translation of these two partne rs at the knee joint is provoked in a defined position using the speci al holding device and under a defined amount of stress. Using this met hod 142 healthy people, placed in different age groups, were tested to establish standard values for the physiological knee joint translatio n. A prearthroscopic stability analysis was performed on 101 patients. Results. This study proves that the special device developed, togethe r with the technique used, provides reliable and exact measurements fo r knee instability in different translation directions. In healthy sub jects the lateral compartment always showed a larger translation than the medial compartment. A gradual increase in translation was determin ed in the age groups over 30 years. A significant difference of 0.0001 was shown between knee stability and instabilities. Moreover, a furth er differentiation between partial and total ACL ruptures and chronic instabilities was determined. This provides an important advantage not offered by usual instrumental testing techniques. Conclusions. The ab ility to diagnose even a very low extent of instability and to differe ntiate between different kinds of instabilities enables exact controls to be carried out for both conservative and operative treatment. Rele vance Establishing the exact extent of knee instability during a norma l clinical examination can be difficult, and this becomes particularly obvious in ensuing check-ups and when comparing test results. Moreove r, in order to be able to decide whether an operation or a series of c heck-ups should be carried out, the exact extent of the knee instabili ty must first be determined, and this is almost impossible to do using common clinical tests. Copyright (C) 1996 Elsevier Science Ltd.