Final answer:
Gastrointestinal disturbance is the side effect that should be discussed with a client prescribed naproxen for osteoarthritis, as NSAIDs like naproxen commonly cause such issues.
Step-by-step explanation:
The potential side effect from naproxen that the nurse should discuss with the client who has osteoarthritis is gastrointestinal disturbance. Naproxen is a nonsteroidal anti-inflammatory drug (NSAID), and this class of drugs is known to cause a variety of side effects including gastrointestinal issues such as indigestion, heartburn, stomach pain, nausea, and a more serious risk of gastrointestinal ulcers and bleeding, particularly with long-term use. Other side effects of NSAIDs can include an increased risk of heart attack and kidney damage, but these are not options listed in your question.
Gastrointestinal disturbance is the most directly related side effect to naproxen use, among the options provided. It is important for the client to be aware of this potential side effect so they can take the medication with food, or discuss alternative treatments with their healthcare provider if they experience any adverse effects.