Bess, an 11-year-old cat suffering arthritis, is put through her paces on an underwater treadmill at the Friendship Hospital for Animals, a veterinary clinic in Washington D.C., the United States. Beyond traditional veterinary treatment, the clinic offers forms of care once reserved for humans, such as acupuncture and therapeutic ultrasound. In the United States, 84.9 million households, or 68 percent, have a pet, according to the American Pet Products Association.Xinhua/AFP