Table 1.

Characteristics and key findings of primary studies evaluating outcomes of early and delayed musculoskeletal injury treatment.

Study	Study Design	Participant Demographics	Definition of Early and Delayed Access to Treatment or Care	Summary of Key Findings
Childs et al. [22]	Retrospective cohort	Participants accessing the U.S. Military Health System (N = 753,450; age range = 18–60 years) for lower back pain (LBP)	Early access: Physical therapy visit occurring within 14 days of primary care index date visit Delayed access: Physical therapy visit occurring between 14–90 days after primary care index date visit	Early access participants who were adherent to physical therapy protocols had significantly lower healthcare use, including lower use of advanced imaging, lumbar spinal injections, lumbar spine surgery, and opioid medications, and lower total LBP-related costs *. * Compared to early (nonadherent), delayed (adherent), and delayed (nonadherent) participants
Ehrmann-Feldman et al. [42]	Prospective cohort	Workers’ compensation cohort from Quebec (Canada) experiencing back injuries (N = 2147)	Early access: Workers receiving physical therapy within 30 days of the injury Delayed access: Workers not receiving, or never referred to physical therapy, or referred more than 30 days following the injury	Receiving early access (i.e., within 30 days) to physical therapy reduced the odds of having an absence from work of more than 60 days following back injury when compared to not receiving early access to physical therapy (aOR = 0.13, 95% CI 0.06–0.3).
Fritz et al. [33]	Randomized Controlled Trial	Patients (general population) with lower back pain attending a primary care physician (N = 220; age range = 18–60 years).	Early physical therapy: Patients commenced treatment within 72 h of study enrolment and received four physical therapy sessions within the initial 4 weeks Usual care: Patients received education on back pain and a resource providing advice consistent with lower back pain guidelines. No further intervention received.	Those receiving early physical therapy had a statistically significant improvement in the Oswestry Disability Index (ODI) at four weeks and at 3 months, but not at 1 year, when compared to those receiving usual care. However, the level of improvement in the early physical therapy group did not reach minimum clinically important differences when compared to levels associated with usual care. Secondary outcomes of the study were mixed, with early care not showing benefits at follow-up time points for pain intensity, physical activity outcomes, and quality of life scales; while patient-reported success and overall health, and fear-avoidance beliefs scales showed significant improvements in the early care group when compared to usual care. There were no differences between groups at follow-up for health care utilisation.
Fritz et al. [36]	Retrospective cohort	Patient (general population) data retrieved from U.S. database of employer-sponsored healthcare plans (N = 32,070), inclusive of new primary care low back pain consultations. Note: patients enrolled in comparative groups share similar population demographic characteristics, index diagnoses, comorbidities, hospitalisations, and/or narcotic use.	Early access: Patients received physical therapy treatment ≤ 14 days following primary care index date. Delayed access: Patients received physical therapy treatment between 15 and 90 days following primary care index date.	Access to early physical therapy referral was associated with decreased levels of healthcare utilisation (advanced imaging, additional physician visits, lumbar spine injections, major surgeries, opioid medication use) and total medical costs when compared to delayed access.
Gellhorn et al. [35]	Retrospective cohort	Patients (general population) who received physician outpatient billing claims relating to lower back pain, sampled from the Centres for Medicare and Medicaid Services (N = 431,195; mean age = 76 years). Note: patients enrolled in comparative groups share similar population demographic characteristics, index diagnoses, comorbidities, and hospitalisations.	Early access (acute): Patients received physical therapy < 4 weeks following index physician visit. Normal access (subacute): Patients received physical therapy 4–12 weeks following index physician visit. Delayed access (chronic): Patients received physical therapy 3–12 months following index physician visit.	Lower risk of later medical service usage among patients who received physical therapy early after a back pain episode when compared to individuals who received physical therapy at later time points. Early physical therapy was strongly associated with decreased use of lumbosacral injections, physician office visits for low back pain, and lumbar surgery, when compared with physical therapy that occurred at later times. The authors also reported a positive dose–response relationship between time until physical therapy treatment commencement and risk of having to experience additional medical intervention.
Horn et al. [59]	Retrospective cohort	Patients (general population) with neck pain complaint presenting to physical therapy clinics in the U.S. (N = 1531; mean age of early treatment group = 46.2 ± 15.4 years, mean age of delayed treatment group = 52.4 ± 16.7 years).	Early management: Patients received physical therapy care < 4 weeks from self-reported symptom onset. Delayed management: Patients received physical therapy care > 4 weeks from self-reported symptom onset.	Early management was associated with increased odds of achieving clinical improvements that represented minimally clinically important differences (MCID) on the neck disability index (aOR = 2.01, 95% CI 1.57–2.56) and the numerical pain rating scale (aOR = 1.82, 95% CI 1.42–2.38) when compared to delayed management (reference group).
Hultman et al. [48]	Non-randomized interventional trial	Swedish patients (general population) presenting to a local hospital emergency department (N = 65; age range = 18–65 years)	Early access (intervention) group: Patients offered physiotherapy visits at 1–14 days (median = 4 days) following ED presentation. Follow-ups relating to outcomes measures were recorded at 3 weeks, 6 weeks, and 3 months. Delayed access (control) group: Patients contacted for follow-ups at 6 weeks and 3 months following ED presentation.	Early access group achieved significant increases (improvements) on the foot and ankle outcome score (FAOS) scale and on questions relating to self-evaluated physical activity and ankle function, at 6 weeks and 3 months, when compared to the delayed access group. No differences between groups were observed in clinical measures relating to joint range of motion, weight-bearing activity, or postural control.
Kucera et al. [56]	Case-control	Union-affiliated carpenters’ compensation claims related to back injuries in Washington State (U.S.); N = 4241.	Early access: Medical care initiated in less than 30 days from date of injury Delayed access: Medical care initiated 30 days or more after date of injury.	A delayed return to work after back injury (>90 days of paid lost work time) was more likely if there was a ≥30-day delay to accessing medical care than when access to medical care occurred sooner (aOR 3.6, 95% CI 2.1–6.1)
Nordeman et al. [37]	Randomized Controlled Trial	Patients (general population) presenting to primary healthcare centers in Sweden with lower back pain (N = 60; mean age of early treatment group = 39.2 ± 12.1, mean age of delayed treatment (control) group = 40.8 ± 11.1).	Early access: Patients received physiotherapy within two days of enrolment in study Control, delayed access: Patients received physiotherapy treatment after 4 weeks following enrolment in study	No significant differences in pain were reported between the groups at discharge. At 6 months of follow-up, pain was significantly lower in the early access group compared to the control group (p = 0.025); however, there were no differences in long-term disability, sick leave, or functional assessment.
Park et al. [51]	Randomized Controlled Trial	Patients (general population) presenting to a South Korean General Hospital with lateral epicondylitis (N = 31; mean age = 50 years)	Early access: Patients received treatment intervention immediately Delayed access: Patients received the treatment intervention after a 4-week period	Early access cohort had significantly greater improvements in pain levels when compared to the delayed group (p < 0.01) at 1 month follow-up time-point. There were no significant differences observed between the groups at 3-, 6-, or 12-month follow-up time points.
Rhon et al. [50]	Retrospective cohort	Individuals receiving care for ankle sprains within the U.S. Military Health System (N = 6150)	The study largely used a statistical approach that did not employ clear cut-points relating to early and delayed rehabilitation. Delay in commencing rehabilitation was instead calculated as a daily effect of each day that passed. One portion of the analysis utilised the following cut-points: Early access: Individuals received care within 4 weeks. Delayed access: Individuals received care within 8–12 weeks.	Receiving delayed rehabilitation increased the odds of a recurrence of ankle sprain when compared to earlier rehabilitation (OR = 1.28, 95% CI 1.10, 1.49). Compared to individuals receiving rehabilitation within 4 weeks, the odds of ankle sprain recurrence in individuals who received rehabilitation between 8–12 weeks were substantially higher (OR = 1.97, 95% CI not reported). Individuals receiving delayed rehabilitation care had greater odds of requiring additional rehabilitation (medical) visits (OR = 1.22, 95% CI 1.16, 1.27). With each additional day of delay in receiving rehabilitation care, there was a linear increase in the associated total treatment costs (OR 1.13, 95% CI 1.10, 1.17).
Rosenfeld et al. [39]	Randomized Controlled Trial	Patients (general population) presenting to primary healthcare centres in Sweden with acute whiplash injuries (N = 89)	Early access: Treatment provided within 96 h of injury Delayed access: Treatment provided after 14 days following injury	There were no significant differences in individual outcome measures associated with early versus delayed access to treatment at 6-month or 3-year follow-up, with passage of time from injury time-point the sole factor associated with pain level and measures of range of motion. However, when considering time to access treatment and treatment type in combination, only early active treatment achieved total cervical ranges of motion 3 years subsequent to their neck injury that matched those of uninjured controls. Those who received delayed access to treatment continued to have reduced cervical range of motion at that 3-year time point.
Rosenfeld et al. [40]	Prospective randomized trial	Patients (general population) presenting to primary healthcare centres in Sweden with acute whiplash injuries (N = 88; mean age of early treatment group = 32, mean age of delayed treatment group = 38).	Early access: Treatment provided within 96 h of injury Delayed access: Treatment provided after 14 days following injury	There were no significant differences in outcomes for early compared to delayed groups, with passage of time following injury the only factor associated with pain levels and measures of range of motion.
Rundell et al. [34]	Prospective cohort	Patients (general population) presenting to primary healthcare settings for a new back pain visit (N = 3705; age ≥ 65 years). Note: This population is outside the active service age for military service members. However, physical function of this age group has a strong bearing on areas of veteran health service delivery.	Early access: Physical therapy initiated ≤ 28 days from index physician visit Delayed access: No form of treatment provided until >28 days from index physician visit	There were no or marginal differences in pain, functional measures, and health-related quality measures at the 3-, 6-, or 12-month follow-up time-points among those who received early access when compared to the matched delayed access group. However, the early access group did have higher odds of improved function at the 12-month time-point (measured via Roland-Morris Disability Questionnaire) when compared to the matched group (OR 1.58, 95% CI 1.04–2.40). NOTE: Total actual received number of physical therapy sessions among the early group was highly variable.
Sohil et al. [32]	Retrospective cohort	Patients (general population) presenting to hospital emergency departments (ED) in Singapore for neck and back pain complaints (N = 125)	Early access: Patients received early physiotherapy evaluation and treatment (EPET) at a median of 4 days from index ED visit. Delayed access: Patients received standard care (SC) at a median of 34 days from index ED visit.	Patients in the early access (EPET) group had significantly lower levels of neck disability (9.0% vs. 33.4%, p < 0.001; measured via the neck disability index questionnaire) and pain (median value 1 vs. 4 points, p < 0.001; measured via the Modified Oswestry Low Back Pain Disability Questionnaire (MODI)) than delayed access (SC) patients (mean delay in treatment of 34 ± 22 days).
Wand et al. [38]	Single-blinded Randomized Controlled Trial	Patients (general population) presenting to primary physician care (i.e., general practitioners or emergency department) in London (England) for acute low back pain (N = 102; 35 ± 8.5 years).	Early access: Patients received immediate physiotherapy treatment following baseline assessment. Delayed access: Patients received treatment at 6 weeks from baseline assessment.	Early access patients demonstrated significantly better levels of disability, mood, general health, and quality of life compared to the delayed access group (p < 0.05) at 6-weeks of follow-up. At longer-term follow-up (i.e., >3 months) there were no significant differences between groups in the primary outcome measures of disability and pain. However, early access group patients did exhibit significantly less anxiety, depressive symptoms, and distress outcomes; and greater ratings of general, mental and emotional health.
Young et al. [49]	Retrospective cohort	Individuals receiving care for patellofemoral pain within the U.S. Military Health System (N = 74,408)	Early access cohort one (i.e., first): Individuals received physical therapy on the same day as diagnosis Early access cohort two (i.e., early): Individuals received physical therapy between 1 and 30 days after initial diagnosis Delayed access: Individuals received physical therapy between 31 and 90 days after initial diagnosis	Reduced odds of requiring additional healthcare (e.g., medical imaging, prescription medications, medical injections) for the diagnosed condition were observed in the early access cohorts (aORs * = 0.09–0.61) when compared to the delayed access cohort (aORs * = 1.64–2.20) [reference for calculation of aORs appears to have been overall cohort]. 2-year total health care costs for patellofemoral pain were significantly lower in the early access cohorts than in the delayed cohort. Odds of injury recurrence were higher in the delayed access cohort (aOR * = 1.78, 95% CI 1.36–2.33) than in the early access (first) cohort (aOR* = 0.55, 95% CI 0.37–0.79). * Statistically significant (p < 0.05).
Zigenfus et al. [41]	Case-control	Workers’ cases of acute low back disorders were extracted from an occupational health care provider database (N = 3867; mean age of early treatment cohort = 35.1 ± 10.4 years, mean age of delayed treatment cohort (1) = 36.4 ± 10.8 years, mean age of delayed treatment cohort (2) = 36.9 ± 11.4 years)	Early access: Workers had an initial physical therapy session within ≤ 1 day of the injury (i.e., day of, or day after initial injury) Delayed access cohort one: Workers had an initial physical therapy session 2–7 days following injury Delayed access cohort two: Workers had a physical therapy session 8–197 days following injury	Early access workers experienced significantly lower numbers of physician visits (p < 0.01), injury case durations (p < 0.01), durations of restricted work (p < 0.01), and days away from work (p < 0.05) compared to both of the delayed access cohorts.

OR: Odds Ratio; aOR: Adjusted Odds Ratio; ED: Emergency Department; SC: Standard Care; EPET: Early Physical Therapy Evaluation and Treatment; MODI: Modified Oswestry Low Back Pain Disability Questionnaire; ODI: Oswestry Disability Index; FAOS: Foot and Ankle Outcome Score: MCID: Minimal Clinically Important Difference; LBP: Lower Back Pain.