Targeting repeated injection users with education interventions aimed at highlighting the extent of their current use and increasing awareness of the oral preparation options may reduce unnecessary injection use. The aim of this retrospective observational study was to investigate the patient factors related to repeated use of injection formulation analgesics in patients with musculoskeletal disorders who were frequent users of ambulatory healthcare services. Population-based national health insurance claims data for the time period July 2011 - December 2011 were analyzed. Patients aged 18 - 80 years with a musculoskeletal disorder, attended ambulatory healthcare settings > 25 times, and were prescribed pain relievers such as non-steroidal anti-inflammatory drugs and narcotic analgesics in an oral formulation for ≥ 14 days or in an injection formulation ≥ 3 times during the study period were included in the study. There were 742,675 repeated systemic analgesic users, and 64.1% (n = 476,021) of these patients were injection users. The average use of injections per patient during the 6-month period was 8.3. Tramadol was the most frequently prescribed medication for injection, followed by diclofenac, piroxicam, and ketorolac. Statistical analyses showed significant correlations between prevalent injection formulation use and patient factors such as gender, age, area of residence, days of healthcare utilization, number of healthcare centers visited, type of healthcare center visited, total medical expenditure, and total out-of-pocket expenditure. These factors could possibly be used to determine the target population for educational interventions aimed at changing behavior relating to the preference for injectable formulations.