Background: Systemic lupus erythematosus (SLE) is a complex autoimmune condition with varied clinical presentations, and musculoskeletal pain is one of the most commonly associated symptoms. However, fibromyalgia (FM) is a prevalent co-existing condition in SLE patients that can also cause widespread pain, and in patients with both conditions, it is often difficult to distinguish the underlying cause of musculoskeletal pain and provide optimal therapy. Methods: A retrospective cohort study was conducted including all adult SLE patients who received musculoskeletal ultrasound (US) examinations for joint pain at the Ohio State University Wexner Medical Center between 1 July 2012, and 30 June 2022. Binary and multiple logistic regression analyses were performed to determine predictors of US-detected inflammatory arthritis as well as improved musculoskeletal pain. Results: A total of 31 of 72 SLE patients (43.1%) had a co-existing diagnosis of FM. In binary logistic regression, a co-existing diagnosis of FM was not significantly associated with US-detected inflammatory arthritis. In multiple logistic regression analysis, clinically detected synovitis was significantly associated with US-detected inflammatory arthritis (aOR, 142.35,p< 0.01), and there was also a weak association with erythrocyte sedimentation rate (ESR) (aOR 1.04,p= 0.05). In separate multiple logistic regression analysis, US-guided intra-articular steroid injection was the only predictor of improved joint pain at follow-up visit (aOR 18.43,p< 0.001). Conclusions: Musculoskeletal US can be an effective modality to detect inflammatory arthritis as well as to guide targeted intra-articular steroid injection to alleviate joint pain in SLE patients with or without FM.