Final answer:
The most relevant question a nurse should ask the client to assess their joint pain effectively is whether their pain level changes after taking medications.
Step-by-step explanation:
When assessing a middle-aged client's joint pain, the most appropriate question for the nurse to ask is: "Does your pain level change after taking medications?" This question directly addresses the impact of interventions on the client's pain and is part of a proper pain assessment, as it can provide crucial information on the effectiveness of the current pain management plan, which may include medications or other therapies. Furthermore, understanding the relationship between medication use and pain relief can be essential in diagnosing and treating joint pain that may be caused by various conditions, such as arthritis or wear and tear due to aging.