CRPS-RISE Outcomes Registry

Inclusion Criteria: * Participants from CRPS-RISE 1. Completion of four infusions of IP (neridronate 100 mg over a \~ 10-day period \[or the renally modified dosing, as applicable\] or placebo) in CRPS-RISE . 2. Completed CRPS-RISE with a final trial visit at Week 6 (Visit 8) or later. Participants who meet both criteria will be provisionally enrolled pending post-trial unblinding and be included in the Provisionally Enrolled Study Cohort. After CRPS-RISE last patient last visit unblinding, only participants who meet the following neridronate exposure criterion #3 will continue in registry follow-up and be included in the Enrolled Study Cohort: 3. Completion of 4-infusions of neridronate 100 mg over approximately a 10-day period in CRPS-RISE. * Participants from the Open Label Extension (OLE) 1. Completion of 4 infusions of neridronate 100 mg over approximately a 10-day period (or the renally modified dosing, as applicable) in the OLE. 2. Completed OLE with a final trial visit at Week 6 (Visit 8) or later. Exclusion Criteria: There are no exclusion criteria.