A criteria-based rehabilitation model emphasizes objective progression markers to guide clinical decision-making and reduce re-injury risk.

Early Rehabilitation Priorities

The initial phase of ACL rehabilitation focuses on restoring foundational joint function and controlling post-operative symptoms.

Key clinical objectives include:

• • Restoration of full knee extension

• • Reduction of pain and effusion

• • Early quadriceps activation

• • Establishment of symmetrical weight-bearing patterns

Weight-bearing progression is influenced by surgical protocols and patient response. Current evidence supports early, controlled loading when tolerated, provided movement quality and symptom response remain appropriate.

Progression Criteria: Moving Beyond TimelineProgression between rehabilitation phases should be determined by measurable clinical criteria, not elapsed time alone.

Common early-phase progression markers include:

• • Full extension with minimal swelling

• • Knee flexion approaching ~120°

• • Straight leg raise without lag

• • Symmetrical gait without compensatory strategies

• • Absence of dynamic valgus during functional tasks

These criteria establish readiness for increased loading and strengthening.

Objective Strength Assessment and Limb Symmetry

Quadriceps strength is a central determinant of functional recovery after ACL reconstruction. Objective strength assessment enables clinicians to quantify deficits and monitor progress across phases.

Handheld dynamometry provides reliable measurement of:

• • Peak force output

• • Limb Symmetry Index (LSI)

• • Strength progression over time

Digital systems such as the Fitmust Digital Dynamometer allow repeatable testing, longitudinal tracking, and clear comparison between involved and uninvolved limbs. Progression to higher-demand phases is typically considered when quadriceps LSI exceeds ~70%, alongside acceptable movement quality.

Strength and Neuromuscular Control Phase

As strength improves, rehabilitation emphasis shifts toward:

• • Closed-chain strengthening

• • Functional squatting patterns

• • Single-limb balance and proprioceptive training

• • Hip and trunk control to reduce knee valgus moments

Interventions are progressed based on movement quality, load tolerance, and symptom response, rather than pre-defined timelines.

Running, Plyometrics, and Functional Testing

Preparation for running and sport-specific activities requires further objective confirmation of readiness.

Key indicators include:

• • Quadriceps and hamstring strength symmetry approaching ~80% LSI

• • Pain-free performance of single-limb tasks

• • Controlled alignment during hopping and change-of-direction drills

• • Resolution of post-exercise symptoms within 24 hours

Hop testing provides valuable insight into limb loading capacity and neuromuscular coordination during higher-velocity tasks.

Psychological Readiness and Confidence

Physical recovery alone does not determine successful RTP. Psychological readiness—including fear of re-injury and confidence under load—plays a significant role in outcomes.

Objective performance data supports psychological recovery by:

• • Providing visible evidence of improvement

• • Reinforcing readiness through measurable benchmarks

• • Improving athlete trust in clinical decision-making

Regular feedback using objective metrics enhances both engagement and compliance.

Return-to-Play Criteria

Final RTP decisions should integrate multiple domains:

• • Strength symmetry ≥95% LSI (via dynamometry)

• • Hop test symmetry ≥95%

• • Acceptable quadriceps-to-hamstring strength balance

• • Absence of pain, swelling, or instability

• • Clean movement patterns during sport-specific tasks

• • Satisfactory psychological readiness measures

Meeting isolated criteria is insufficient; comprehensive readiness across domains is essential.

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Clinical Implications

A criteria-based ACL rehabilitation framework:

• • Reduces reliance on subjective assessment

• • Improves communication with athletes and coaching staff

• • Supports defensible RTP decisions

• • Aligns with modern sports medicine standards

Objective measurement tools such as digital dynamometry play a critical role in enabling consistent, data-driven progression.