Two independent medical practices in Minnesota once hoped to expand operations but have spent the past year struggling to recover from the cyberattack on a vast UnitedHealth Group payment system.

Odom Health & Wellness, a sports medicine and rehabilitation outfit, and the Dillman Clinic & Lab, a family medicine practice, are among the thousands of medical offices that experienced sudden financial turmoil last year. The cyberattack against Change Healthcare, a division of United, paralyzed much of the nation’s health-care payment system for months.

Change lent billions of dollars to medical practices that were short on cash but has begun demanding repayments.

Dillman and Odom are suing United in U.S. District Court in Minneapolis, accusing the corporation of negligence related to the cyberattack and claiming they sustained excessive expenses because of the attack’s fallout.

In addition, Odom and Dillman asserted in court filings that the company’s insurance arm, UnitedHealthcare, has in turn been denying claims to cover patient care for being submitted late.

Lawmakers viewed the chaos caused by the cyberattack as a result of United’s seemingly insatiable desire to buy up companies like Change, alongside doctors’ practices and pharmacy businesses. The widespread disruption was a reminder of how deeply United’s sprawling subsidiaries had become embedded in the nation’s health care system.