Jack Russell Terrier can suffer from dislocated kneecaps (luxating patellas), eye problems, deafness, and Legg - Perthes disease, a disease of the hip joints. (puppiesndogs.com)
Gundogan dislocated his kneecap in training at the start of May and was also sidelined for the 2014 World Cup with a back problem that ruled him out for almost the entire 2013 - 14 season. (bbc.com)
Other health concerns include dislocated kneecaps, back problems, cataracts, low blood sugar, eye irritations, and possible problems with whelping. (puppiesndogs.com)