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Mobility data from the Apple Health app may serve as a valuable tool for assessing patient recovery following surgery for traumatic injuries of the lower extremity, such as tibial plateau, distal femur, and femoral shaft fractures, according to a study presented at the 2025 Annual Meeting of the American Academy of Orthopaedic Surgeons.

Using mixed-effect models to compare certain Apple Health mobility parameters, the researchers were able to objectively measure improvement by using a patient’s mobility data prior to injury as a baseline metric.

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“Our goal as orthopaedic surgeons is to help patients regain mobility and resume the activities they enjoy,” said Dane J. Brodke, MD, MPH, an assistant professor at Oregon Health & Science University in Portland and one of the study authors.

“In cases of traumatic leg injuries, assessing functional recovery has traditionally been challenging due to a lack of objective data. Since smartphone-based platforms like Apple Health collect data passively in the background, we have a unique opportunity to measure mobility both before and after an injury, providing valuable context for patient recovery. This baseline information is vital to contextualizing a patient’s recovery and is generally unavailable with other functional outcome measures.”

Comparing Pre- and Post-Injury Data

The cross-sectional study aimed to assess whether the outcome measures from Apple Health captured mobility changes associated with injury and early recovery, correlated with patient-reported outcomes (PROs), and could distinguish between patients with and without nonunion.

The authors included adult patients with lower extremity fractures who owned iPhones and had at least 6 months of post-injury follow-up. Participants shared Apple Health data and completed Patient Reported Outcomes Measurement Information System (PROMIS) surveys to analyze physical function and pain.

The key metrics analyzed included:

• Daily step count
• Walking asymmetry
• Double support time
• Walking speed
• Step length

Using mixed-effects models, the researchers compared mobility parameters at 3 critical time points:

• Pre-injury (28 days prior)
• Acute post-injury (first 28 days after injury)
• 6 months post-injury (days 152-180)

Correlations between mobility parameters and PROMIS physical function and pain interference were assessed.

Study Findings

As the researchers expected, the study found that all 5 Apple Health mobility parameters showed significant changes from pre-injury to post-injury:

• Step count decreased by 93%
• Walking speed decreased by 9%
• Step length decreased by 6%
• Walking asymmetry increased by 88%
• Walking double support increased by 1%

Six months following the injury, the team observed the following improvements:

• The average daily step count was 2,430, a 655% increase from early post-injury, but a 52% decrease from pre-injury.
• Walking speed and step length continued to decrease during the first 6 months of recovery, while walking asymmetry and double support time increased.
• Compared with pre-injury, walking asymmetry remained 198% higher and speed 15% lower.

Step count was the only mobility parameter to show a moderate or stronger correlation with patient-reported physical function. Notably, patients with nonunion] demonstrated a 55% slower recovery in daily step counts compared to those who healed normally.

Study Implications

“These finding suggest that smartphone-measured step counts not only correlate with adverse clinical outcomes, but may also predict them, allowing for earlier intervention and improved patient care,” said study author Nathan O’Hara, PhD, MHA, an associate professor of orthopaedics at University of Maryland Medical System in Baltimore.

“Conversely, when a patient’s recovery plateaus, it may indicate they have reached their maximum potential improvement. While the PROMIS survey offers valuable insights from a patient’s perspective, it remains subjective. For the first time, the objective data from Apple Health provides a clearer, more reliable understanding of a patient’s recovery.”

The team is currently developing an app that patients can download during their initial orthopaedic surgeon visit, with the goal of enrolling more participants to track their Apple Health data. By leveraging this technology, the team hopes to empower patients with personalized insights that support their recovery and help them safely return to an active lifestyle.

Source

Brodke DJ, Sheer B, O’Hara N. The future is mobile: validating apple health as a novel orthopaedic trauma outcome metric. Presented at the 2025 Annual Meeting of the American Academy of Orthopaedic Surgeons, March 10-14, 2025, in San Diego, California.