Osteoarthritis of the knees in mice is a genetically governed disease in which multiple genes are involved. They have an overall recessive behavior without major sex linkage. Genetic dissociation between the joint disease, obesity and plasma lipids is demonstrated. Osteoarthritis del genu in le mus es un geneticamente regulate morbo in que multiple genes es interessate. 1110s es, in lor generalitate, de comportamento recessive e es libere de major ligage sexual. Es demonstrate dissociation genetic inter le morbo articular, obesitate, e lipidos del plasma.
HAT DEGENERATIVE JOINT DISEASE is genetically influenced has
T been suggested both by clinical studies of Heberden's nodes in man1 and by the demonstration of strain differences in the occurrence of osteoarthritis in mice.2 The following studies were carried out in an attempt to characterize the inheritance cf the lesions in mice and their relationship to several other genetically influenced attributes. The special features studied most intensively dealt for the most part with certain aspects of lipid metabolism that are reported ~eparately.~ In addition, however, body size, weight, sacral polymorphism, coat color, hemoglobin and hematocrit, hepatoma and pulmonary adenoma formation have been analyzed.
METHODS AND MATERIALS Experimental Procedures
Three inbred parent lines4 were studied: STR/lN, DBA/2JN and A/LN. The STR/lN ( hereafter designated S ) mice were selected because they consistently developed severe spontaneous osteoarthritis of the knees, and the A/LN ( A ) strain because it regularly does not. DBA/2JN ( D ) mice frequently have osteoarthritis of milder degree than the s animals. Reciprocal crosses were made between the S and D and between the S and A mice. Matings were designed to provide 25 individuals of each of the parent lines ( P ) : 50 of each reciprocal F, cross; 100 F,' s from each of the F, reciprocal crosses; and 100 each of the two types of back-crosses ( B C ) to each parental line. Figure 2 indicates all types of matings made, the female parent being listed first. Inasmuch as the experiments were terminated when the animals were 16 months old, approximately 50 per cent in excess