When Nick began 2018, it was with good posture and mobility. As the year progressed, Nick began to display indications of low back and hip arthritis. The primary indication is that that standing posture slowly deteriorates from an erect stand to a slouch like that shown in the featured image. Note that neither rear paw is being dragged or knuckling over during gait. Gait is normal but maybe bowlegged or somewhat stiff.
Low back and hip arthritis is common in greyhounds and in humans. As with humans, it reduces quality of life by causing pain that the critter accommodates by reducing activity volume and diversity.
As with humans, there are things you can do to maintain quality of life including use of supplements, pain management via medication, and physical therapies such as acupuncture. After the break, the Head Moocher will talk about what is helping Nick.