Participants in Phase 1 of this study will be separated into the following four groups: people with OA and insomnia; people with OA, but without insomnia; people without OA, but with insomnia; and people without OA or insomnia. All participants will attend two study visits. During Visit 1, participants will complete questionnaires and an interview and will provide a urine sample and a set of recent x-rays. A diary, which will be used to record activity levels for 2 weeks, will also be given to all participants.