The tuberositas tibiae and extension in the knee joint.

In all 56 tibiae from Lapps and 56 from Norwegians have been studied. These ethnic groups represent different weight bearing situations. Variables dealing with the extension in the knee joint are dealth with. The bone is mainly studied in the AP and the ML planes. The material is analyzed statistically. The distribution form is examined and the deviations from normality are found to be moderate. Chiefly positive skewness occurs. Platykurtosis is found equally often as leptokurtosis. The deviations from a standard normal distribution are not supposed to affect the results significantly. There is a non-systematic pattern of distribution. The variability is generally lower in Lapps than in Norwegians. The variability is about the same in linear and angular variables and in indices. In linear variables females and Lapps show lower mean values than males and Norwegians, respectively. Lapps show the largest indices. In linear variables, contrary to in angular variables and indices, the sex differences exceed the differences between the ethnic groups. As a rule sex differences are largest in Lapps. The variations of the tuberositas tibiae are supposed to be in particular the results of muscular forces in bone remodeling. The relationship between the habitual knee position and extension is discussed.