My Wife Has Experienced Sharp Shoulder Pain For About A

My wife has experienced sharp shoulder pain for about a year. She describes it as "like a needle in the joint". This is not a constant pain, but she has episodes with ever increasing frequency. Each episode lasts about 3-5 days. She will not take NSAIDs. She says that one aspirin helps some. She has not had a chest X-ray. She quit smoking 40 years ago. (She is now 69) Do you have any idea as to what she should do to investigate this pain? She has a primary care physician.