The effect of early physical therapy intervention on case duration and physical therapy visits in acute work-related musculoskeletal injuries across body regions: A retrospective cohort study

Abstract

OBJECTIVE:

To evaluate how initiating physical therapy (PT) early affected (1) case duration and (2) the number of PT visits, in patients with acute work-related musculoskeletal disorders (WMSDs).

DESIGN:

A retrospective cohort study of 83 846 patients with WMSDs who were receiving occupational health services between January 1, 2021, and December 31, 2022.

METHODS:

Patients were categorized according to the time from injury to initiating PT (0–2 days, 3–7 days, 8–12 days, and 13+ days). Descriptive statistics were used to analyze case duration and PT visits across 7 diagnostic groups (lumbar spine, thoracic spine, cervical spine, shoulder/humerus, elbow/wrist/hand, knee, and ankle/foot). Kruskal-Wallis tests assessed the impact of PT timing on outcomes.

RESULTS:

Initiating PT early (0–2 days) was associated with significantly shorter case durations and fewer PT visits across all diagnostic groups. The median case duration for early PT was 14 days, compared to 28 days for initiating PT later (13+ days). Similarly, the early PT group required fewer PT visits (median: 4) than the late PT group (median: 5). These trends were consistent across all diagnostic groups.

CONCLUSION:

Initiating PT early, particularly within the first 2 days postinjury, was associated with shorter case durations and fewer PT sessions in people with acute WMSDs. Standardizing early PT protocols in occupational health settings could improve case durations and reduce health care use.

Work-related musculoskeletal disorders (WMSDs) result from physical activities in the workplace such as lifting, pulling, pushing, falling, and repetitive motions.¹⁴ WMSDs have a profound impact on workers and the broader economy. Overexertion injuries in the workplace cost US employers $12.49 billion anually.⁹ The overall financial burden of work-related injuries in the United States was $167 billion in 2022, which included lost wages and productivity, medical costs, and administrative expenses.^3,11

Given the substantial financial and societal impact of WMSDs, interventions that expedite recovery and minimize costs are vital. Physical therapy (PT) is a key intervention in managing WMSDs, with the primary goal of restoring function, reducing pain, and helping injured workers return to their jobs as quickly and safely as possible.^5,10 Patients who start PT soon after injury experience faster recovery, fewer complications, and lower overall health care costs.^{4,9,10,12,14,15} Initiating PT within 1 day of injury for lower back pain resulted in fewer physician visits, earlier discharge from the work-related health care episode, and fewer days with restricted work capacity compared to those who delayed PT for 8 days or more.¹⁸ Similarly, starting PT within 2 days of a lower back injury was linked to a shorter work-related health care episode, while delaying PT beyond 7 days led to poorer outcomes.² Early PT in military and primary care settings is also associated with reduced odds of advanced imaging, surgery, and prescription opioid medications.^1,2,6,14,15

While there is substantial evidence supporting the positive impact of early PT over “wait and see” approaches—which have been suggested in United States practice guidelines and reported clinical practice patterns¹²—there is no agreement on what constitutes “early” PT. Some define early PT as treatment within 0–14 days of injury, while others extend the window to 30 days or more.^1,6 The variability in definitions makes it difficult to establish standard treatment protocols and identify the ideal timeframe to initiate PT after an injury.

Much of the literature supporting early PT intervention is focused on spinal conditions, specifically neck and lower back pain. However, some studies have examined the effects of early PT on extremity injuries.^1,4,5,12,16 Injuries affecting the upper and lower extremities may present different rehabilitation challenges and recovery timelines compared to spinal injuries. A better understanding of the impact of early vs delayed PT across spinal and extremity conditions has important implications for treatment protocols, patient outcomes, and costs associated with WMSDs.

The primary aim of this study was to assess how different timing intervals for initiating PT after a work-related injury affect the overall case duration and the number of PT visits.

METHODS AND DATA SOURCE

The data examined in this study included 108 644 injured workers seen at an integrated occupational health system (Concentra Medical Centers [Concentra]) across the United States from January 1, 2021, to December 31, 2022. Patients included in the study had a single WMSD classified under the International Classification of Diseases, 10th Revision (ICD-10) attached to their case and were referred to PT. The study was reviewed by the Institutional Review Board at Northern Arizona University. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist was used to guide the reporting of this study.¹⁷

Data were extracted from an electronic health record (Altera Touchworks) from patient cases seen in a Concentra occupational health location over a 2-year period from 2021 through 2022. All patients received collaborative ambulatory medical and therapy services within the Concentra system (locations across 41 states). Patients were initially evaluated by a primary care clinician with a physician license of MD (Doctor of Medicine), DO (Doctor of Osteopathic Medicine), PA (Physician Assistant), or NP (Nurse Practitioner). The primary care clinician determined if PT was needed based typically on a musculoskeletal condition with clear work-related cause. Objective musculoskeletal impairments observed during examination included, but were not limited to loss of strength, loss of range of motion and/or gait deviations, and a functional deficit noted that prevents the patient from working regular and customary duties.

Case inclusion criteria for the study were (1) age 18 to 65 years, (2) a WMSD with a single ICD-10 code, (3) referred to PT, and (4) completed all PT and medical visits within the Concentra system. Case exclusion criteria for the study were (1) age <18 or >65 years at time of injury, (2) nonmusculoskeletal conditions (eg, traumatic brain injury), (3) cases referred to PT with 2 or more ICD-10 codes, (4) cases referred to specialist outside of the occupational health system (eg, surgeon), (5) cases that did not have their first medical visit within 30 days of date of injury, and (6) cases that were closed and reopened were also excluded. A cutoff of 30 days was chosen to include only acute WMSD. Cases with multiple ICD-10 diagnosis codes were excluded to ensure accurate tracking of outcomes within a single body region. For example, if a patient sustained both a lumbar spine and shoulder injury, it would not be possible to determine when each injury improved individually—only when the entire work-related health care episode was closed. By limiting cases to a single ICD-10 code, we aimed to isolate the impact of PT timing on recovery within a specific body region. A total of 83 846 cases met these criteria.

The study variables were case duration, PT visits, and days from injury to the first PT visit (see TABLE 1). The primary outcome, case duration, was defined as the number of days from the initial medical visit to case closure, which occurred when the patient returned to prior functional status, achieved maximal medical improvement, and was released from the work-related episode by a medical clinician. The secondary outcome, PT visits, was measured as the total number of physical therapy sessions attended. The key independent variable, days from injury to the first PT visit, was categorized into 4 groups: 0–2 days, 3–7 days, 8–12 days, and 13 or more days. These categories were chosen to build upon prior work.^2,18 Our analysis expands their approach to other body regions beyond the spine to determine whether similar timing patterns affect recovery across different types of injuries.

TABLE 1.

Study Variables and Definitions

Variable	Definition	Measurement/Category
Case duration	Days from initial medical visit to medical case closure and release from care	Median (IQR) reported Range also presented
PT visits	Total number of PT sessions attended per patient	Median (IQR) reported Range also presented
Time to PT initiation	Days from injury to PT evaluation	Categorized as: 0–2 days, 3–7 days, 8–12 days, 13+ days
Diagnostic groups	Injury location based on ICD-10 coding	Lumbar spine, elbow/wrist/hand, shoulder/humerus, ankle/foot, knee, thoracic spine, cervical spine
Age	Patient’s age at the time of injury (in years)	Mean (SD) reported
Sex	Patient’s self-reported sex (male or female)	% Male, % Female

Abbreviations: ICD-10, International Classification of Diseases, Tenth Revision; IQR, interquartile range; PT, physical therapy; SD, standard deviation.

Based on the ICD-10, the dataset included 83 846 cases of work-related musculoskeletal injuries, categorized into 7 diagnostic groups: ankle/foot (grouped together), knee, lumbar spine, thoracic spine, cervical spine, shoulder/humerus (grouped together), and elbow/wrist/hand (grouped together). The grouped body regions were combined secondary to coding protocols within the informatics system that made it impossible to create more discrete groups. For each case, data were extracted on the number of days from injury to the first PT visit, total case duration (in days), and the total number of PT visits. Additionally, data were collected for the median total number of PT visits and case duration for each diagnostic group.

Statistical Analysis

Descriptive statistics were calculated for case characteristics and outcomes. Comparisons were made based on diagnostic group, days from medical evaluation to PT evaluation, median total number of PT visits, and median case duration in days. Informed consent was obtained, and the rights of participants were protected.

Descriptive statistics were used to summarize the data, with median values and interquartile ranges (IQRs) presented for nonnormally distributed variables such as case duration and PT visits. Due to the large sample size, normality was evaluated through visual inspection (ie, Q-Q plots and density distributions) and statistical test (ie, Shapiro-Wilk test). Case duration and PT visits normality plots and tests indicated nonnormal distribution skewed heavily to the right due to multiple extreme outliers. Thus, median and IQR, along with the Kruskal-Wallis tests (ie, nonparametric test of ranks), were used to account for the nonnormal distribution. The analysis was stratified by the diagnostic group to examine the impact of PT timing on outcomes across different diagnostic groups. A Kruskal-Wallis 1-way analysis of variance by ranks test was calculated to examine whether days from injury to first PT visit influenced Case Duration across all cases and within individual diagnostic groups. Data were analyzed using R statistical software. Characteristics of data analyzed are listed in TABLE 2.

TABLE 2.

Sample Characteristics (N = 83 846)

Characteristic	N (%)
Age in years (mean (SD))	38.7 (12.7)
Sex
Male	53 567 (63.9%)
Female	30 279 (36.1%)
Diagnostic group
Lumbar spine	31 718 (37.8%)
Elbow/wrist/hand	14 676 (17.5%)
Shoulder/humerus	14 204 (16.9%)
Ankle/foot	13 954 (16.6%)
Knee	5933 (7.1%)
Thoracic spine	1752 (2.1%)
Cervical spine	1609 (1.9%)
Time to initiation of PT
0–2 days	31 460 (37.5%)
3–7 days	28 514 (34.0%)
8–12 days	11 006 (13.1%)
13+ days	12 866 (15.3%)

Abbreviations: PT, physical therapy; SD, standard deviation.

RESULTS

There were 108 644 patients with a single ICD-10 WMSD who were referred to PT seen in Concentra Medical Centers from January 1, 2021, to December 31, 2022; 83 846 met our selection criteria. The mean age of the study population was 38.7 years (SD, 12.7), and 36.1% were females (see TABLE 2). Patients were separated by diagnostic group, with most in the lumbar spine (37.8%), elbow/wrist/hand (17.5%), shoulder/humerus (16.9%), and ankle/foot (16.6%) diagnostic groups. Based on the timing of initiation of PT, a majority of patients fell in the 0- to 2-day (37.5%) and 3- to 7-day (34.0%) categories. See TABLE 3 for PT initiation breakdown within each diagnostic group.

TABLE 3.

Number of Patients by Diagnostic Group and Days From Injury to First PT Visit

Diagnostic Group	Total N	0–2 Days From Injury to PT Evaluation	3–7 Days From Injury to PT Evaluation	8–12 Days From Injury to PT Evaluation	13+ Days From Injury to PT Evaluation
All groups	83 846	31 460 (37.5%)	28 514 (34.0%)	11 006 (13.1%)	12 866 (15.3%)
Lumbar spine	31 718	12 019 (37.9%)	11 306 (35.7%)	4098 (12.9%)	4295 (13.5%)
Elbow/wrist/hand	14 676	5041 (34.3%)	4719 (32.2%)	2091 (14.3%)	2825 (19.3%)
Shoulder/humerus	14 204	5106 (36.0%)	4726 (33.3%)	1901 (13.48%)	2471 (17.4%)
Ankle/foot	13 954	5780 (41.42%)	4689 (33.60%)	1687 (12.09%)	1798 (12.9%)
Knee	5933	2116 (35.76%)	1963 (33.19%)	828 (14.0%)	1026 (17.3%)
Thoracic spine	1752	742 (42.4%)	594 (33.9%)	213 (12.2%)	203 (11.6%)
Cervical spine	1609	656 (40.8%)	517 (32.1%)	188 (11.7%)	248 (15.4%)

Abbreviation: PT, physical therapy.

Case Duration

The median case duration for the entire study population was 17 days (IQR, 10–29). The median case duration for 0–2 days was 14 (IQR, 8–23), 3–7 days was 17 (IQR, 10–27), 8–12 days was 21 (IQR, 14–33), and 13+ days was 28 (IQR, 18–43). There was a statistically significant difference in case duration between the timing of PT initiation groups, χ²(3) = 8302.6, P<.001; all groups were significantly different from each other (P<.001). Cohen’s d effect sizes were calculated for each comparison (TABLE 4). The difference between 0–2 days and 13+ days was large (d = 0.9), whereas the differences between 0–2 days and 8–12 days (d = 0.5), and between 3–7 days and 13+ days (d = 0.7) were medium. The same trend was observed across each individual diagnostic group. See TABLE 5 and APPENDICES A–G for details on each individual diagnostic group.

TABLE 4.

Post Hoc Comparison of Case Duration by Days From Injury to PT

			Comparison Effect Size d
Days From Injury to PT Evaluation	Median Case Duration in Days (IQR)	Range in Days	0–2 Days	3–7 Days	8–12 Days	13+ Days
0–2 days	14 (8–23)	1–340	-	0.2a	0.5a	0.9a
3–7 days	17 (10–27)	1–723	-	-	0.3a	0.7a
8–12 days	21 (14–33)	1–266	-	-	-	0.4a
13+ days	28 (18–43)	1–438	-	-	-	-

Abbreviations: IQR, interquartile range; PT, physical therapy.

Bonferroni p value adjustment used. Cohen’s d effect size thresholds are 0.2 for small, 0.5 for medium, and 0.8 for large.

^aP<.001.

TABLE 5.

Case Duration by Days From Injury to PT for All Diagnostic Groups

Diagnostic Group	0–2 Days From Injury to PT Evaluation Median (IQR)	3–7 Days From Injury to PT Evaluation Median (IQR)	8–12 Days From Injury to PT Evaluation Median (IQR)	13+ Days From Injury to PT Evaluation Median (IQR)
All diagnostic groupsa	14 (8–23)b,c,d	17 (10–27)e,f	21 (14–33)f	28 (18–43)
Lumbar spinea	14 (8–24)b,c,d	16 (10–27)e,f	21 (13–32)g	28 (17–42)
Elbow/wrist/handa	14 (7–23)b,c,d	17 (10–27)e,f	22 (14–35)g	30 (19–47)
Shoulder/humerusa	14 (8–25)b,c,d	17 (10–29)e,f	22 (14–36)g	28 (18–44)
Ankle/foota	13 (7–23)b,c,d	17 (10–27)e,f	21 (14–33)g	29 (19–44)
Kneea	14 (8–24)b,c,d	17 (10–28)e,f	22 (14–34)g	28 (19–42)
Thoracic spinea	11 (6–18)b,c,d	14 (9–23)e,f	19 (12–30)g	27 (17–43.5)
Cervical spinea	10 (6–19)b,c,d	15 (9–24)e,f	18 (12–30)g	23 (15–38)

Abbreviations: IQR, interquartile range; PT, physical therapy.

^aKruskal-Wallis test significant, P<.001.

^b0–2 days significantly different than 3–7 days, P<.001.

^c0–2 days significantly different than 8–12 days, P<.001.

^d0–2 days significantly different than 13+ days, P<.001.

^e3–7 days significantly different than 8–12 days, P<.001.

^f3–7 days significantly different than 13+ days, P<.001.

^g8–12 days significantly different than 13+ days, P<.001.

PT Visits

The median number of PT visits was 4 (IQR, 2–6). Based on the timing of initiation of PT, the median number of PT visits for 0–2 days was 4 (IQR, 2–6), 3–7 days was 4 (IQR, 3–6), 8–12 days was 5 (IQR, 2–6), and 13+ days was 5 (IQR, 3–6). There was a statistically significant difference in PT visits between the timing of PT initiation groups, χ2(3) = 138.3, P<.001; all groups were significantly different from each other (P<.001), except there was no difference between 3–7 days and 8–12 days (P = 1.00) (see TABLE 6). The effect sizes were all trivial. The same trend was not observed across each individual diagnostic group. The knee group was not significant; within the cervical spine group, the effect sizes for each comparison to 0–2 days were all larger than those in each diagnostic group and all groups together (TABLE 7 and APPENDICES H–N).

TABLE 6.

Post Hoc Comparison of PT Visits by Days From Injury to PT

			Effect Size d
Days From Injury to PT Evaluation	Median PT Visits (IQR)	Range	0–2 Days From Injury to PT Evaluation	3–7 Days From Injury to PT Evaluation	8–12 Days From Injury to PT Evaluation	13+ Days From Injury to PT Evaluation
0–2 days	4 (2–6)	1–28	-	0.05a	0.06a	0.11a
3–7 days	4 (3–6)	1–34	-	-	0.01	0.07a
8–12 days	5 (2–6)	1–35	-	-	-	0.06a
13+ days	5 (3–6)	1–44	-	-	-	-

Abbreviations: IQR, interquartile range; PT, physical therapy.

Bonferroni P value adjustment used. Cohen’s d effect size thresholds are 0.2 for small, 0.5 for medium, and 0.8 for large.

^aP<.001.

TABLE 7.

PT Visits by Days From Injury to PT for All Diagnostic Groups

Diagnostic Group	0–2 Days From Injury to PT Evaluation Median (IQR)	3–7 Days From Injury to PT Evaluation Median (IQR)	8–12 Days From Injury to PT Evaluation Median (IQR)	13+ Days From Injury to PT Evaluation Median (IQR)
All diagnostic groupsa	4 (2–6)d,e,f	4 (3–6)g	5 (2–6)h	5 (3–6)
Lumbar spineb	5 (3–6)k	5 (3–6)	5 (3–6)	5 (3–6)
Elbow/wrist/handa	4 (2–6)d,e,f	4 (2–6)g	4 (2–6)	5 (2–6)
Shoulder/humerusa	4 (2–6)f,i,j	5 (3–6)g	5 (3–6)	5 (3–6)
Ankle/foota	4 (2–6)f,i	4 (2–6)	4 (2–6)	5 (2–6)
Kneec	4 (2–6)	4 (2–6)	5 (2.75–6)	5 (3–6)
Thoracic spinea	4 (2–6)k	4 (2–6)	4 (3–6)	4 (3–6)
Cervical spinea	3 (2–5)d,f,j	4 (3–6)	5 (2–6)	5 (2.75–6)

Abbreviations: IQR, interquartile range; PT, physical therapy.

^aKruskal-Wallis test significant, P<.001.

^bKruskal-Wallis test significant, P<.05.

^cNot significant.

^d0–2 days significantly different than 3–7 days, P<.001.

^e0–2 days significantly different than 8–12 days, P<.001.

^f0–2 days significantly different than 13+ days, P<.0010.

^g3–7 days significantly different than 13+ days, P<.001.

^h8–12 days significantly different than 13+ days, P<.001.

ⁱ0–2 days significantly different than 3–7 days, P<.05.

^j0–2 days significantly different than 8–12 days, P<.05.

^k0–2 days significantly different than 13+ days, P<.05.

DISCUSSION

The timing of initiating PT affected case duration across all diagnostic groups. Initiating PT early (within 0–2 days postinjury) was associated with shorter case durations. Delays in initiating PT were associated with progressively longer case durations. This suggests that early PT expedited return to work and reduced the overall burden on health care systems by minimizing the number of sessions required.

Other studies have also examined the effects of early versus delayed PT intervention on health care use outcomes, such as case duration and the number of PT visits, with similar conclusions.^{1,2,4,7,12,13} In our analysis, the median case duration was 17 days, with the earliest intervention group (0–2 days) achieving the shortest duration (14 days) and the delayed intervention group (13+ days) experiencing the longest duration (28 days). These findings align with both those of Zigenfus et al¹⁸ and Horne and Fritz.⁷ Zigenfus¹⁸ found that their early PT group (0–2 days) for low back pain had the shortest mean case duration of 29 days, compared to 47 and 79 days in the moderately delayed (3–7 days) and significantly delayed (>7 days) groups, respectively. Similarly, Horne and Fritz⁷ assessed PT initiation in patients with neck pain and found a median duration of 49 days for early PT (within 14 days), compared to 139 days for delayed PT (15–90 days). While both studies demonstrated the same trend—longer case durations with delayed PT—the overall median case durations in our study were shorter, possibly due to differences in injury type, treatment protocols, or health care settings.

In terms of PT visits, the median number of sessions in our sample was 4, with the delayed groups (8–12 and 13+ days) requiring a median of 5 visits. These findings are consistent with those of Zigenfus,¹⁸ who reported that the early PT group required an average of 6 visits, compared to 9 and 12 visits for the moderately and significantly delayed groups, respectively. Horne and Fritz⁷ found a median of 3 visits in the early PT group and 4 visits in the delayed group. Similarly, Childs et al⁴ observed a mean of 7.3 visits in individuals with acute low back pain who received early PT (within 14 days). While the number of PT visits remained relatively stable across intervention timings, early initiation significantly shortened overall case duration. Starting PT earlier was beneficial, as it prevented the prolonged case durations, which typically accompanied delayed intervention, while maintaining a manageable number of visits.

The magnitude of benefit from early PT appears to be consistent across various body regions, with early intervention leading to reductions in both case duration and the number of PT visits. While the effects of early PT were most pronounced in the initial treatment phases, trends showed improvements across all diagnostic groups, reinforcing the broad applicability of early PT as an effective strategy. This is consistent with previous studies where early PT demonstrated positive effects in reducing opioid use in patients with shoulder, knee, and lower back pain.¹⁶

In Concentra’s integrated occupational health facilities, medical clinicians and physical therapists practiced in the same facility and used the same electronic health record (Touchworks). This interprofessional communication facilitated early identification and management of individuals who are unlikely to respond well to PT, while also identifying those ready for discharge, which reduces unnecessary health care use. This approach is supported by Helms et al,⁸ who emphasized the importance of interprofessional collaboration to improve patient outcomes. Prompt referral to PT services should be prioritized, particularly in cases of high-risk musculoskeletal injuries, to improve recovery and reduce disability. Standardizing early PT interventions across different body regions could drive more consistent and efficient health care use.

Limitations

The study was retrospective, used data from a single health care delivery system, and may not have direct translation to all health care systems treating occupational injuries. Date of injury was self-reported by patients, which may be inaccurate. Patients only had a single ICD-10 code associated with their case, which means we did not account for more complex injuries to multiple body regions or systems. Patients referred to specialists were excluded because we could not accurately track their case durations. This analysis did not control acute versus acute exacerbation of a chronic condition and only considered date of reported injury. There was no control over therapist or medical interventions applied. Number of PT visits and length of care were measured, no specific outcome or physical capability measures were included.

CONCLUSION

Starting PT early was a key determinant of favorable outcomes in work-related musculoskeletal injuries. Initiating PT early significantly reduced case durations and the number of PT visits across all diagnostic groups of WMSDs. Individuals who began PT within 0–2 days had a median case duration of 14 days, increasing to 17 days for those who initiated PT within 3–7 days, 21 days for those who started between 8–12 days, and 28 days for cases where PT was delayed for 13 or more days. The early PT group required a median of 4 visits compared to 5 visits for those who started later.

KEY POINTS.

FINDINGS:

Initiating PT early significantly reduced case duration across various body regions. Delays in initiating PT were associated with longer case durations and more PT sessions, indicating that early intervention was important for reducing case duration and more efficient use of health care resources.

IMPLICATIONS:

By initiating PT early, health care systems can potentially reduce the overall burden of work-related musculoskeletal injuries, decrease case durations, and reduce unnecessary health care resource use. Standardizing early PT practices could drive more consistent and effective rehabilitation, benefiting both patients and employers.

CAUTION:

The study’s retrospective nature and reliance on data from a single health care system limits the generalizability of the results. Variations in therapist practices and the lack of specific outcome measures constrain the applicability of the findings to other settings and injury types.

DATA SHARING:

Deidentified patient data used in this study are available upon request. These data are governed by a data-sharing agreement between Northern Arizona University and Select Medical Corporation. Requests for access to these data should be directed to the corresponding author (Michael Morgan via email at Michael.t.morgan@nau.edu). Data may be reused for research purposes in compliance with the terms of the agreement and applicable regulations.