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More than 45 p. cent of patients with degenerative knee arthritis are obese. The overweight is more marked when the medial tibio-femoral and the lateral femoro-patellar aspects are affected. With the same degree of weight gain, the relationship between obesity and degenerative knee arthritis is more marked in women than in men. The significance of the overweight increases the probability of developing degenerative knee arthritis, increasing its functional severity. The obesity precedes the arthritis, and is not its consequence. It is a mechanical effect by increase of the articular strains. It is unknown how long the obesity must be present in order to be pathogenic for the knee and what functional and anatomical improvement may be expected from a weight loss.

Teleradiographic examinations of the lower limb, from the frontal position with the patient standing, were conducted in 50 men over 65 years of age who had never had painful knees. One knee (out of 100) was found to have an internal femoro-tibial arthrosis. The femoro-tibial angle in the arthrosis-free knees was -0.27" (+/- 2.83 degrees) on the right and -1.10" (+/- 3.05 degrees) on the left. The mean femoro-tibial angle was -0.68" (standard deviation 2.9 degrees), and normal values are therefore -5.5 degrees to +5.1 degrees. There was no evidence, therefore, of statistically significant physiological genu valgum in the population studied. Marginal osteophytes and tibial spines are frequently observed and have no pathological significance. A meniscochondrocalcinosis was present in 8 percent of the subjects.

Radiographs were taken in profile, and femoropatellar axial projection with 60 degrees flexion, in 50 men over 65 years of age who had never complained of symptoms related to their knees. Visible osteophytes of the patella are very frequently noted in profile radiography and were present in 35 subjects. Painless femoropatellar arthrosis is also frequent and this was noted on 60 degrees axial radiography in 7 subjects; unilaterally in 3 cases and bilaterally in 4 subjects. In 9 cases the femoropatellar arthrosis was external, while in 2 cases it was present both externally and internally. Detection of a patellar osteophyte on profile radiography does not necessarily imply the existence of femoropatellar arthrosis detectable radiologically on axial projection. This study was also able to define values for a certain number of the parameters of radiological morphology of the knee.

Statistical comparison of the weight index of patients presenting arthritis of the knee with that of a control group of matching sex and age, has enabled to demonstrate a definite weight gain in the most frequent topographical varieties of knee arthritis in women: lateral femoro-patellar, medial femoro-tibial, combination of the two. In men, the excess weight was only demonstrated in medial femoro-tibial arthritis.

Fifty women over 65 who had never suffered from knee problems had a frontal teleradiography of the lower limbs in a vertical standing position. Two knees (out of one hundred) were affected by an external femoro-tibial arthrosis. The femoro-tibial angle of the knees without arthrosis was very close to 0 (0.02). The typical difference was 2.46. The normal level is thus approximately -5 to +5 degrees, and there was thus no "physiological" genu-valgum in the population studied. Marginal osteophytosis and the tibial spines is very frequent and has no pathological significance. A menischondrocalcinosis was found in 14 per cent of subjects.

Measurement of the femorotibial angle was performed in 244 patients (134 women and 110 men) without knee arthrosis with roentgenograms taken in the upright position. The values were grouped according to sex and to decade of life. The average value was approximately 0. As defined by the average upper and lower values of the two types of angulation, the normal value in women was 4 degrees of varus and 4 degrees of valgus. In men, the normal value of the right leg was 5 degrees of varus and 5 degrees of valgus; the left leg demonstrated up to 6 degrees of varus and 5 degrees of valgus. After sixty years of age, 5 percent of patients had angulation above these normal values in valgus and varus.