After improving knee range of motion (ROM) and quadriceps activation, reducing pain and swelling, and normalizing walking in Phase 1: Protect & Activate, Phase 2 focuses on building strength, improving control, and preparing the body for higher-level activity—including the eventual return to running.
At Evolve Physical Therapy, we continue our criterion-based progression. Our ACL rehab protocol follows a progressive, systematic approach, ensuring that each phase of recovery is based on objective milestones rather than time alone:
Phase 2 (Weeks 7–16): Strength & Control
Goals:
- Achieve full, symmetrical knee range of motion
- Restore lower extremity strength (especially quadriceps) to 80%
- Reinforce normalized walking mechanics
- Improve neuromuscular control and balance
- Prepare for the return to running
Aim of Phase 2:
The goal of Phase 2 ACL reconstruction rehabilitation is to build strength and control while maintaining proper mechanics, protect the integrity of the repair, and prepare the knee for higher-level activity. Progress should be measurable every 2–3 weeks, with improvements in loading capacity and tolerance assessed using hand-held dynamometer (HHD) testing and Limb Symmetry Index (LSI). This structured progression ensures the knee is ready for Phase 3: Dynamic Strength & Running.
Limb Symmetry Index (LSI) Testing
A key component of Phase 2 is the objective measurement of lower-extremity strength using the Limb Symmetry Index (LSI). LSI compares the strength of the surgical leg to the non-surgical leg, providing a clear benchmark for progress. At Evolve Physical Therapy, we use a hand-held dynamometer (HHD) to measure quadriceps, hamstring, and hip strength.
For Phase 2, the target is at least 80% limb symmetry, meaning the surgical leg is at least 80% as strong as the uninvolved leg. This ensures patients are developing sufficient strength to safely progress toward running, functional movements, and eventual return-to-sport testing in later phases. LSI testing also guides exercise selection and load progression to optimize recovery and prevent compensatory patterns.
Building on Phase 1
Before entering Phase 2, patients should demonstrate:
- Full knee extension and improving flexion
- Minimal to no swelling or pain
- Normalized walking mechanics
- Strong quadriceps activation
- Ability to ambulate with normalized mechanics (with or without assistive devices)
- Readiness to progress into strengthening and controlled loading
These milestones ensure readiness for increased loading and progression.
Restoring Full Range of Motion
Phase 2 continues to emphasize symmetrical knee motion, ensuring:
- Full extension is maintained
- Flexion is restored to match the uninvolved side
This is critical for efficient movement and future running mechanics.
Progressive Strength Training
Phase 2 is where meaningful strength gains occur.
Key areas include:
- Quadriceps strengthening
- Glute and hip strength
- Hamstring co-contraction
- Core stability
Exercises include:
- Single-leg squats:
We emphasize movement quality and control over load.
Reinforcing Normal Walking
Even after gait is restored in Phase 1, Phase 2 ensures it becomes automatic and symmetrical under load.
Focus includes:
- Equal weight distribution
- Full knee extension during stance
- Elimination of subtle compensations
This is essential before introducing higher-impact activities, such as running.
Preparing for Running with the Boost 3
A major milestone in Phase 2 is preparing the body for running. At Evolve Physical Therapy, we use the Boost 3 Microgravity Treadmill to introduce running in a controlled, reduced-bodyweight environment—often beginning around week 12, once patients meet the appropriate criteria.
Benefits include:
- Reduced joint stress during initial running
- Ability to maintain proper mechanics
- Gradual reintroduction of impact
- Increased patient confidence
This allows for a safer and more progressive transition into running compared to traditional methods.
Neuromuscular Control & Balance
Patients continue to develop:
- Single-leg stability
- Proprioception
- Movement coordination
These are essential for safely progressing into dynamic activity.
Criteria to Progress to Phase 3
Patients must demonstrate:
- Full, symmetrical ROM
- Minimal to no swelling
- Strong quadriceps and lower extremity strength at 80% LSI
- Proper mechanics with functional movements
- Readiness for running progression
Next step: Phase 3: Dynamic Strength & Running
Common Mistakes
- Progressing too quickly due to reduced pain
- Ignoring subtle gait compensations
- Inadequate quadriceps strength
- Attempting to run before meeting criteria
The Big Picture
Phase 2 builds the strength and control necessary for higher-level activity. By preparing for and introducing running using the Boost 3 Microgravity Treadmill and monitoring objective strength with LSI testing, patients can transition safely into Phase 3 while minimizing stress on the healing knee and reducing the risk of setbacks.
Evidence-Based, Patient-Centered Care
We are committed to using evidence-based practices at Evolve Physical Therapy to ensure optimal recovery following ACL reconstruction. Our comprehensive rehabilitation program integrates scientific research, cutting-edge technology, and individualized care to help our patients return to their daily activities and sports safely and efficiently.
If you or someone you know is undergoing ACL reconstruction, contact us today to learn how we can support your recovery journey with our expert-led rehabilitation services.
Thank you for reading Optimizing ACL Reconstruction Rehab: A Comprehensive, Evidence-Based Approach | Phase 2.
We will have new blog posts focusing on Phases 3 and 4 in the coming months. Stay tuned!
Our physical therapists have advanced training in sports injuries, including hands-on (manual therapy) soft-tissue treatment, joint mobilization, joint manipulation, and progressive exercise. Our comprehensive evaluation and one-on-one treatment go beyond alleviating symptoms; we strive to have you return to the sports and activities you love. Visit our Sports Injuries page for more information.
For a thorough evaluation and individualized treatment, contact our Physical Therapy Sherwood clinic or our Physical Therapy Bethany clinic today and be seen in less than 48 hours.
More Posts in This Series:
- Optimizing ACL Reconstruction Rehab: A Comprehensive, Evidence-Based Approach | Phase 3 (With Videos)
- Optimizing ACL Reconstruction Rehab: A Comprehensive, Evidence-Based Approach | Phase 2 (WITH VIDEOS)
- Optimizing ACL Reconstruction Rehab: A Comprehensive, Evidence-Based Approach | Phase 1 WITH VIDEOS
