Dogs usually wear their feelings—such as pain—on their sleeves, but cats keep theirs close to the vest. That makes it tough to identify feline discomfort—say, from arthritis.

A study of joint disease in cats showed the vast majority of our feline friends—even those less than a year old—have X-ray signs of arthritis involving at least one joint. A common way for their pain to manifest is through reduced activity and subtle behavior changes. For example, where your cat used to readily leap off a counter, now she might inch her way down instead.

Once you notice the changes, you can help your veterinarian treat your cat by recording your buddy’s activity on your phone, preferably in slow motion. Then whatever the treatment plan, documenting the changes can help determine if it’s working.