Acute ankle sprain & rehabilitation (OSGAR-2) – Effectiveness of a sensorimotor training intervention - individually adjusted by functional diagnostic parameters - on ankle joint function after first-time acute lateral ankle sprain.

Status:

completed 11/2025

Aims:

Acute lateral ankle sprains with structural damage to the lateral ligament complex are among the most common injuries in sports and everyday life and are associated with high recurrence rates and a substantial risk of chronic ankle instability. Insufficient early objective functional assessment and the lack of structured, function-based rehabilitation are considered major contributors. The OSGAR II project aimed (1) to develop a valid and sensitive diagnostic inventory to detect functional ankle instability shortly after a primary acute lateral ankle sprain (OSGAR II.1) and (2) to evaluate the short- and long-term effectiveness of a multimodal sensorimotor training pro-gram (SMART) compared with standard-care (NORMT) (OSGAR II.2).

Activities/Methods:

This was a prospective, single-center study with two consecutive modules:

OSGAR II.1 (Diagnostics): controlled cross-sectional design using matched pairs comparing injured participants (IN-JURED; n=36) with healthy controls (CONTROL; n=36). From a multidimensional test battery (patient-reported out-comes, range of motion, gait/running, postural control, strength, jump/landing), the most discriminative parameter per domain was selected. Cut-offs were determined using ROC curves and the Youden index.

OSGAR II.2 (Training): randomized controlled longitudinal trial with 6- and 12-month follow-up. Individuals with a primary acute lateral ankle sprain underwent MRI 1–2 weeks post-injury to classify ligament severity and confirm eligibility (inclusion: significant lesion/rupture of ≥1 lateral ligament; exclusion: fractures, syndesmotic injury, oste-ochondral lesions, etc.). Participants were randomized to SMART (6-week progressive multimodal sensorimotor program starting 2–3 weeks after injury; supervised + home-based sessions; low-cost equipment) or NORMT (symp-tom-based physiotherapy/standard-care). Primary outcomes were CAIT and FAAM assessed at baseline (T1), post-intervention (T2), 6 months (T3), and 12 months (T4). Statistics: repeated-measures ANOVA with post-hoc tests (Bonferroni corrected).

Results:

OSGAR II.1: A practical diagnostic inventory with domain-specific cut-offs was established for early identification of functional instability. Key thresholds included CAIT <26, FAAM-Sport <86, reduced passive plantar-flexion (<44°) and total passive ROM (<72°), impaired postural control (SEBT composite <92.81), reduced concentric plantarflexion strength (<2.24 Nm/kg), altered jump/landing performance (drop-jump contact time >0.23 s), and gait-related indicators.

OSGAR II.2: Both groups improved substantially over time. For CAIT, a significant time×group interaction favored SMART, indicating faster recovery to clinically unremarkable levels in the SMART group (on average from T2) com-pared with NORMT (on average from T3). FAAM-Sport also showed a significant interaction with a steeper improve-ment in SMART. Over 12 months, 38% reported at least one recurrent sprain (SMART n=12; NORMT n=16); 9% met criteria consistent with chronic instability, predominantly in the NORMT group (SMART n=1; NORMT n=5).

Relevance and usability for statutory accident insurance and practice: The diagnostic inventory supports early screening (2–3 weeks) and deficit-guided rehabilitation planning. SMART provides a structured, low-threshold program (handout/PDF, QR-coded videos, home training, minimal equipment) that is feasible for routine implementation. Earlier functional recovery and potential reductions in recurrence/chronicity may help lower long-term costs (time off work, repeated injuries, persistent symptoms).

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