Tarsal joint contracture in dogs with golden retriever muscular dystrophy.

Golden retriever muscular dystrophy (GRMD) is an X-linked myopathy homologous with Duchenne muscular dystrophy of human beings. Affected dogs have progressive clinical dysfunction due to muscle wasting and contractures. Deficits progress particularly rapidly between 3 and 6 months of age. To better characterize the role of contractures in this deterioration, the flexor surface, nonweight-bearing tarsal joint angle was measured in GRMD-affected dogs and clinically normal littermates at both ages. The mean +/- SD tarsal joint angle for clinically normal dogs decreased from 164.6 +/- 6.09 degrees to 145.6 +/- 8.80 degrees between 3 and 6 months (P < 0.0005). The value for GRMD-affected dogs decreased from 153.3 +/- 11.44 degrees to 117.6 +/- 24.55 degrees (P < 0.005). The angle for clinically normal dogs was greater than that for GRMD-affected dogs at both ages (P < 0.05 at 3 months and P < 0.01 at 6 months). The decrease in tarsal joint angle, at times to less than 90 degrees, correlated well with other phenotypic features of GRMD, such as loss of the ability to walk.