Time to First Injury After Knee Surgery in U.S. Army Soldiers: A Survival Analysis

Area of Science:

• Military medicine
• Orthopedic surgery
• Musculoskeletal injury epidemiology

Background:

• Knee injuries are a significant cause of disability in U.S. Army soldiers, often requiring surgical intervention.
• Existing research on post-surgical injury risk predominantly focuses on civilian populations, lacking military-specific timing data.

Purpose of the Study:

• To pinpoint peak injury risk periods following knee surgery in active-duty soldiers.
• To test the hypothesis that injury risk escalates around return to duty and persists post-rehabilitation.

Main Methods:

• Utilized U.S. Army administrative and medical data from the Soldier Performance, Health, and Readiness database.
• Employed an accelerated failure time model, adjusting for demographic, surgical, and military factors, to assess post-operative injury risk by procedure type.

Main Results:

• 71% of 7595 soldiers undergoing knee surgery (2017-2020) experienced a new musculoskeletal injury within 4 years.
• Peak injury risk occurred approximately 2.5 months post-surgery, coinciding with the lifting of physical activity restrictions.
• Soldiers with prior non-knee injuries were re-injured 11% sooner; a secondary injury likelihood increased around 14.3 months post-surgery.

Conclusions:

• Identified critical windows for injury prevention strategies around the end of rehabilitation and at 1 year post-surgery.
• Findings have implications for guiding clinical care, informing military post-operative policy, and enhancing long-term soldier outcomes.