Anterior Cruciate Ligament (ACL) Rehabilitation: A Complete Guide

Understanding the Anterior Cruciate Ligament (ACL)

What is the ACL?

The anterior cruciate ligament (ACL) is a critical component of the knee joint, playing a vital role in stabilising the knee by preventing the tibia (shinbone) from sliding too far forward relative to the femur (thighbone). Additionally, the ACL helps control rotational movements and resists excessive side-to-side movements, contributing to overall knee stability.

Anatomy of the Knee and the ACL

The knee joint is comprised of three primary bones: the femur, the tibia, and the patella (kneecap). The ACL extends from the femur to the tibia, crossing diagonally in the middle of the knee. This ligament not only provides mechanical stability but also contains mechanoreceptors that contribute to proprioception—the body’s ability to sense joint position and movement.

The Role of the ACL in Knee Kinematics

The ACL is responsible for approximately 85% of the restraining force against anterior tibial translation and plays a significant role in preventing excessive tibial rotation and varus/valgus stresses. Due to its intricate function, an ACL injury is often considered a neurophysiological dysfunction rather than merely a peripheral musculoskeletal injury. This highlights the importance of a comprehensive rehabilitation programme to address both the physical and neurological aspects of knee stability.

Common Causes and Types of ACL Injuries

How Does an ACL Injury Occur?

ACL injuries are typically caused by sudden stops, changes in direction, awkward landings from a jump, or direct collisions. These types of movements are common in sports such as football, basketball, skiing, and rugby. Women are two to eight times more likely to sustain an ACL injury compared to men, often due to anatomical and hormonal differences that affect knee stability.

Types of ACL Injuries

• Mild Sprains: Involve partial tears of the ACL, leading to minor knee instability and pain.

• Severe Tears: Occur when the ligament is completely ruptured, causing significant instability and often requiring surgical intervention.

Associated Knee Injuries

ACL injuries rarely occur in isolation. They can be accompanied by damage to other structures within the knee, such as the medial collateral ligament (MCL), menisci, cartilage, or even result in microfractures and bone contusions. The presence of these additional injuries necessitates a tailored rehabilitation approach to ensure comprehensive recovery.

Goals of ACL Rehabilitation

The primary objectives of ACL rehabilitation are to:

1. Restore Full Range of Motion (ROM): Ensuring the knee can move freely without restriction.

2. Rebuild Muscle Strength: Strengthening the quadriceps, hamstrings, and other muscles supporting the knee.

3. Enhance Proprioception: Improving the body’s ability to sense joint position and movement for better stability.

4. Achieve Functional Stability: Ensuring the knee can support daily activities and sports-specific movements without instability.

5. Facilitate Return to Activity: Enabling a safe return to pre-injury levels of physical activity and sports.

Phases of ACL Rehabilitation

ACL rehabilitation is typically divided into several phases, each with specific goals and exercises designed to progressively restore knee function and strength.

1. Acute Phase (Weeks 1-2)

Objectives:

• Reduce pain and swelling

• Restore full knee extension

• Begin gentle flexion exercises

Key Interventions:

• PEACE & LOVE Protocol:

  • Protection: Avoid activities that may aggravate the injury.

  • Rest: Minimise use of the injured knee.

  • Ice: Apply ice packs for 10-15 minutes every few hours to reduce swelling.

  • Compression: Use a knee brace or compression bandage to manage swelling.

  • Elevation: Elevate the leg above heart level to decrease swelling.

  • Load: Gradually introduce weight-bearing activities as tolerated.

  • Optimism: Maintain a positive outlook to support the healing process.

  • Exercise: Begin gentle range of motion and strengthening exercises as pain permits.

Exercises:

• Passive Knee Extension: Assisted by a physiotherapist to achieve full extension.

• Heel Slides: Gently bending the knee while lying down.

• Quadriceps Sets: Isometric contractions to activate the quadriceps without moving the knee.

2. Pre-Surgical Phase or Conservative Treatment (Weeks 3-6)

Objectives:

• Maintain and improve ROM

• Enhance muscle strength and endurance

• Improve proprioception and balance

Key Interventions:

• Strengthening Exercises: Focus on the quadriceps and hamstrings to support the knee.

• Proprioceptive Training: Balance exercises using stability boards or single-leg stands.

• Gait Training: Ensuring a normal walking pattern to avoid compensatory movements.

Exercises:

• Static Quadriceps Contractions: Holding the muscle contraction without movement.

• Hamstring Curls: Strengthening the hamstrings by bending the knee against resistance.

• Balance Exercises: Standing on one leg or using a balance board to improve stability.

3. Post-Surgical Rehabilitation (Weeks 1-12)

Objectives:

• Protect the surgical site

• Restore ROM and muscle strength

• Begin functional training

Key Interventions:

• Early Weight Bearing: Gradually increasing the amount of weight placed on the injured knee.

• Closed Kinetic Chain (CKC) Exercises: Such as squats and leg presses to build functional strength.

• Open Kinetic Chain (OKC) Exercises: Controlled knee extensions to isolate the quadriceps.

Exercises:

• Heel Raises: Strengthening the calf muscles.

• Leg Presses: Building overall leg strength.

• Isometric Exercises: Maintaining muscle engagement without knee movement.

4. Advanced Rehabilitation (Months 3-6)

Objectives:

• Achieve full knee ROM

• Restore muscle strength to pre-injury levels

• Improve functional performance and sport-specific skills

Key Interventions:

• Plyometric Training: Jumping and bounding exercises to enhance explosive power.

• Agility Drills: Quick direction changes to mimic sports movements.

• Sport-Specific Training: Exercises tailored to the demands of the individual’s sport.

Exercises:

• Jumping Drills: Controlled jumps to build power and coordination.

• Agility Ladders: Enhancing footwork and quickness.

• Resistance Training: Using weights and resistance bands to further strengthen the knee.

5. Return to Sport (Months 6-9)

Objectives:

• Ensure knee stability and strength are sufficient for sports participation

• Minimise the risk of re-injury

• Achieve optimal performance levels

Key Interventions:

• Functional Testing: Assessing knee strength, stability, and performance through hop tests and agility drills.

• Gradual Return to Activity: Slowly increasing participation in sports-specific activities while monitoring knee response.

• Maintenance Program: Ongoing exercises to maintain knee health and prevent future injuries.

Exercises:

• Hop Tests: Single-leg hops to evaluate strength and stability.

• Cutting and Pivoting Drills: Mimicking sports movements to ensure readiness.

• Endurance Training: Building stamina to support prolonged physical activity.