Zdravniški Vestnik (Nov 2004)
INSTRUMENTAL MEASUREMENT OF KNEE LAXITY IN ANTERO-POSTERIOR DIRECTION
Abstract
Background. A magnitude of clinical tests (like Lachman test) are used to diagnose antero-posterior knee instability. They are easy to preform but they are very subjective. An experienced practitioner is often required. An alternative to standard clinical tests is the usage of arthrometer which requires a cooperative patient (maximal relaxation of thigh muscles).The aims of this study were to assess the antero-posterior laxity of both knees in the normal population (population without prior injury to the knee) and to determine knee laxity in terms of total relaxation (usage of miorelaxant) under general anaesthesia. We compared the difference between the left and right knee of the same individual and the influence of ageing and gender on knee laxity. We also studied the influences of diabetes and long-term corticosteroid therapy.We wanted to prove the following theories: complete relaxation of thigh muscles has an effect on measurement of knee laxity; the individual without prior knee injury has no statistically side to side difference; the laxity increases with age; women have grater ligamentous laxity than men; laxity increases as the result of diabetes and also as a result of longterm corticosteroid therapy.Methods. Arthrometer KT 1000/STM (Medmetric) was used in our survey. We analysed 90 individuals (aged 18–81) who haven’t had knee injuries in the past.Among them were 45 (50%) men and 45 (50%) women. 8 (8.9%) of them were diabetics and 4 (4.4%) of them received long-term corticosteroid therapy.We assessed the antero-posterior laxity of both knees of an individual under the effect of general anaesthetic. Each measurement was repeated thrice. The same procedure was used to determinate antero-posterior laxity without the usage of anaesthetic.Results. We concluded that muscle relaxation affects the antero-posterior laxity of the knee (all the differences were statistically significant, p < 0.001). Side to side difference was minimal (statistically unsignificant, p > 0.05). The average laxity between men and women showed no difference. We obtained the same results considering age. We couldn’t prove the effects of long-term corticosteroid therapy and diabetes on knee laxity.Conclusions. Our study has showed the importance of muscle relaxation on knee laxity. An individual who hasn’t experienced any knee trauma has practically no side to side difference. Women and men have the similar knee laxity, so do the younger and older individuals. Individuals on longterm corticosteroid therapy and those with diabetes showed no difference as compared to normal population. In a cooperative patient knee laxity under general anaesthetic (total muscle relaxation) approaches the one when awake. The difference is clinically irrelevant. Therefore we assume that arthrometer is very useful, particularly in measurements under the effect of anaesthetic. Comparison between men/women requires detailed investigation including hormone status and muscle strenght. The effect of age, diabetes and longterm corticosteroid therapy should be studied on a more representative sample.
