Algorithm Based ACL Rehabilitation

Justin Shaginaw MPT, ATCRevised 11/13/05

Algorithm Based ACL Rehabilitation

Justin Shaginaw MPT, ATCRevised 11/13/05

IntroductionIntroduction

Common contact and non-contact injury in athletes100,000 new cases annually (Bach, Boonos)Previously meant season ending, if not career ending injuryAthletes are returning to pre injury levels, at times within the same seasonOutcomes are accomplished through a post operative program focusing on functional rehabilitation and neuromuscular control activities

Common contact and non-contact injury in athletes100,000 new cases annually (Bach, Boonos)Previously meant season ending, if not career ending injuryAthletes are returning to pre injury levels, at times within the same seasonOutcomes are accomplished through a post operative program focusing on functional rehabilitation and neuromuscular control activities

Anatomy & BiomechanicsAnatomy & Biomechanics

ACL• 2 bands: anteromedial &

posterolateral• Functions

• Primary restraint to anterior tibial translation

• Significant restraint to hyperextension

• Limits tibial internal rotation

• Secondary restraint to varus/valgus stresses

ACL• 2 bands: anteromedial &

posterolateral• Functions

• Primary restraint to anterior tibial translation

• Significant restraint to hyperextension

• Limits tibial internal rotation

• Secondary restraint to varus/valgus stresses

PCL• 3 bundles:

Anteriolateral, Intermediate & Posteriomedial

• Functions• Primary restraint to

posterior tibial translation

• Secondary restraint to hyperextension & varus /valgus stress

PCL• 3 bundles:

Anteriolateral, Intermediate & Posteriomedial

• Functions• Primary restraint to

posterior tibial translation

• Secondary restraint to hyperextension & varus /valgus stress

MCL• 2 Layers: superficial and

deep• Functions

• Primary restraint to valgus stress

• 57 % at 0°• 78% at 25°

LCL• Functions

• Restraint to varus stress• 55% at 0°• 69% at 30°

MCL• 2 Layers: superficial and

deep• Functions

• Primary restraint to valgus stress

• 57 % at 0°• 78% at 25°

LCL• Functions

• Restraint to varus stress• 55% at 0°• 69% at 30°

Anatomy & Biomechanics

Medial Meniscus• Semi lunar or C shaped• Extensive capsular

attachmentLateral Meniscus• Circular shape• Minimal capsular

attachmentMeniscal functions• Shock absorption• Joint lubrication and

nutrition• Joint stability

Medial Meniscus• Semi lunar or C shaped• Extensive capsular

attachmentLateral Meniscus• Circular shape• Minimal capsular

attachmentMeniscal functions• Shock absorption• Joint lubrication and

nutrition• Joint stability

Anatomy & Biomechanics

Surgical ConsiderationsSurgical Considerations

Procedure• “Mini-open” vs all

arthroscopicGraft type• Autograft vs allograft

Fixation• Boney vs soft tissue

Graft properties• Tensile strength• Stiffnes

Graft “Ligamentization”

Procedure• “Mini-open” vs all

arthroscopicGraft type• Autograft vs allograft

Fixation• Boney vs soft tissue

Graft properties• Tensile strength• Stiffnes

Graft “Ligamentization”

Graft PropertiesGraft Properties

3023391Posterior TibialisTendon

4632352Quadriceps Tendon

7764108Quadruple Hamstring

8122376Bone Patella Bone

2422160Intact ACL

Stiffness (N/mm)Ultimate Strength (N)

From presentation by Arthur Bartolozzi MDFrom presentation by Arthur Bartolozzi MD

Fixation PropertiesUltimate Tensile Load (N)

Fixation PropertiesUltimate Tensile Load (N)

725-1600Cross-pin Technique

768Tandem Soft Tissue Washers

1126 Bone Mulch Screw

341 +/- 163Bioabsorbable Screw (7mm)

242 +/- 90 Metal Interference Screw (7mm)

588Staples

565Bioabsorbable Screw (9mm)

330-418Bioabsorbable Screw (7mm)

330-418Metal Interference Screw (15mm)

328Metal Interference Screw (13mm)

302Metal Interference Screw (11mm)

276 +/- 436Metal Interference Screw (9mm)

640 +/- 201Metal Interference Screw(7mm)

Direct Soft TissueDirect Soft Tissue Direct BoneDirect Bone

From presentation by Arthur Bartolozzi MDFrom presentation by Arthur Bartolozzi MD

Post Op EvaluationPost Op Evaluation

ROMStrengthGirth Patella mobilityObservationSwelling/joint effusionLachman’sGaitOther special tests

ROMStrengthGirth Patella mobilityObservationSwelling/joint effusionLachman’sGaitOther special tests

Protocol vs Algorithm Based Rehab

Protocol vs Algorithm Based Rehab

Protocols• Rehab programs that are usually

time based• Often times separated into

accelerated and non-accelerated programs

Algorithms• Allow all patients to follow the

same rehabilitation guidelines progressing according to specific goals irrespective of time frames

• “Phases” of algorithm based rehab

Protocols• Rehab programs that are usually

time based• Often times separated into

accelerated and non-accelerated programs

Algorithms• Allow all patients to follow the

same rehabilitation guidelines progressing according to specific goals irrespective of time frames

• “Phases” of algorithm based rehab

Protocol vs Algorithm Based Rehab

Protocol vs Algorithm Based Rehab

Protocol• Were developed according to

biological healing times• Based on time frames

Algorithm• Goal based rehab• Based on objective and

functional goals Algorithm allows for a more appropriate progression for each individual patient

Protocol• Were developed according to

biological healing times• Based on time frames

Algorithm• Goal based rehab• Based on objective and

functional goals Algorithm allows for a more appropriate progression for each individual patient

Initial Post Op PhaseInitial Post Op Phase

Goals to be achieved• PROM 0°-110°• Full active extension• Minimal joint effusion• Normal gait• Good quad control/tone• Normal patella mobility

Goals to be achieved• PROM 0°-110°• Full active extension• Minimal joint effusion• Normal gait• Good quad control/tone• Normal patella mobility

GaitGait

Focus on normal heel to toe patternStart with bilateral crutches and brace open to available AROMProgress out of brace before off of crutches

Focus on normal heel to toe patternStart with bilateral crutches and brace open to available AROMProgress out of brace before off of crutches

Proprioception & Neuromuscular Control

Proprioception & Neuromuscular Control

Three inputs: visual, tactile, vestibular• Try to challenge all three

Unilateral standing activities: slight knee flexion to eliminate stability from boney congruence and screw home mechanismLook to progress to activity/sport specific balance exercises“Toys”: Dyandisc, wobble board, foam pad, physioball, BOSU, balance beam

Three inputs: visual, tactile, vestibular• Try to challenge all three

Unilateral standing activities: slight knee flexion to eliminate stability from boney congruence and screw home mechanismLook to progress to activity/sport specific balance exercises“Toys”: Dyandisc, wobble board, foam pad, physioball, BOSU, balance beam

Strengthening and Muscle Re-Education

Strengthening and Muscle Re-Education

Quad tone/control• Russian/neuromuscular electric

stimulation with quad set during supine extension stretch

Strengthening• Initiate exercises focusing on

single plane/single muscle group• Progress to multiple

plane/multiple muscle group exercises

• Include proprioceptive/ neuromuscular control component

• Look to include activity/sport specific exercises

Quad tone/control• Russian/neuromuscular electric

stimulation with quad set during supine extension stretch

Strengthening• Initiate exercises focusing on

single plane/single muscle group• Progress to multiple

plane/multiple muscle group exercises

• Include proprioceptive/ neuromuscular control component

• Look to include activity/sport specific exercises

Strengthening ProgressionStrengthening Progression

Mini Squats → Leg Press →Unilateral Leg Press → Leg Press on Disc/Foam Roll/BallLeg Raises → Hip Machine → Walking/Stepping with TherabandProne Hamstring Curls →Standing Curls → Resisted Curls → Bilateral Curls on Physioball → Unilateral Curls on Physioball

Mini Squats → Leg Press →Unilateral Leg Press → Leg Press on Disc/Foam Roll/BallLeg Raises → Hip Machine → Walking/Stepping with TherabandProne Hamstring Curls →Standing Curls → Resisted Curls → Bilateral Curls on Physioball → Unilateral Curls on Physioball

Joint EffusionJoint Effusion

Some benefit with modalities initiallySign of healing within the jointWarmth sign of acute inflammationMonitor changes in joint effusion to assess tolerance with rehab program

Some benefit with modalities initiallySign of healing within the jointWarmth sign of acute inflammationMonitor changes in joint effusion to assess tolerance with rehab program

Controlled Activity PhaseControlled Activity Phase

Goals to be achievedFull strength with manual muscle testingNo joint effusionPROM 0°-125° +Passing isokinetic test at 85%Passing functional hop test at 85%Running initiated in this phase

Goals to be achievedFull strength with manual muscle testingNo joint effusionPROM 0°-125° +Passing isokinetic test at 85%Passing functional hop test at 85%Running initiated in this phase

Proprioception & Neuromuscular Control

Proprioception & Neuromuscular Control

Progress sport specific activitiesInitiate speed ladder for agility and foot workInitiate weight acceptance/attenuation activitiesMust develop limb confidence

Progress sport specific activitiesInitiate speed ladder for agility and foot workInitiate weight acceptance/attenuation activitiesMust develop limb confidence

Neuromuscular ControlNeuromuscular Control

Replicate demands place on lower extremityInclude activity specific inputBe creative and think activity/sport/position specific!

Replicate demands place on lower extremityInclude activity specific inputBe creative and think activity/sport/position specific!

StrengtheningStrengthening

Incorporate neuromuscular control componentWork on both muscle power and enduranceIsokinetic exercises

Incorporate neuromuscular control componentWork on both muscle power and enduranceIsokinetic exercises

Criteria to Initiate Running ProgramCriteria to Initiate Running Program

Isokinetic test at least 75% of uninvolved No patellofemoral symptomsNo joint effusion Start on treadmill; progress to outside due to running mechanics

Isokinetic test at least 75% of uninvolved No patellofemoral symptomsNo joint effusion Start on treadmill; progress to outside due to running mechanics

Return to Sport/Activity Phase

Return to Sport/Activity Phase

Slow progression into practices• Simple straight plane

drills• Progress to

multidirectional drills• Non-contact

progressing to contact drills

Follow up isokinetic testing as indicated

Slow progression into practices• Simple straight plane

drills• Progress to

multidirectional drills• Non-contact

progressing to contact drills

Follow up isokinetic testing as indicated

Advanced TrainingAdvanced Training

Initiated during Return to Sport/Activity Phase of post operative rehabilitationRemember training should include both rehabilitation and integration into practice

Initiated during Return to Sport/Activity Phase of post operative rehabilitationRemember training should include both rehabilitation and integration into practice

Advanced TrainingAdvanced Training

Goals are to return theathlete to pre injurylevels

• Neuromuscular control

• Strength• Endurance• Power• Limb confidence• Sport specific skills

Goals are to return theathlete to pre injurylevels

• Neuromuscular control

• Strength• Endurance• Power• Limb confidence• Sport specific skills

Lower Extremity Strength and Conditioning

Lower Extremity Strength and Conditioning

Must return to pre injury levels of strength, power, and enduranceMust be sport specific as well as position specificMany athletes return to sport activities prior to reaching pre injury levelsShould be based on principals of periodization

Must return to pre injury levels of strength, power, and enduranceMust be sport specific as well as position specificMany athletes return to sport activities prior to reaching pre injury levelsShould be based on principals of periodization

PeriodizationPeriodization

Strength and conditioning program based on cyclic program of work and recovery/rest phasesIs systematic, sequential, and progressiveMust integrate individual’s rehabilitation program into team’s/coach’s seasonal program

Strength and conditioning program based on cyclic program of work and recovery/rest phasesIs systematic, sequential, and progressiveMust integrate individual’s rehabilitation program into team’s/coach’s seasonal program

Lower Extremity Strength

Lower Extremity Strength

Strength: the ability to exert maximum forceCan be assessed manually, isokineticallyor in weight roomSAID principleContinuation of rehabilitation exercisesShould incorporate dynamic exercises

Strength: the ability to exert maximum forceCan be assessed manually, isokineticallyor in weight roomSAID principleContinuation of rehabilitation exercisesShould incorporate dynamic exercises

Lower Extremity Endurance

Lower Extremity Endurance

Endurance: ability to maintain optimal levels of strength, power and neuromuscular controlNeeds to be sport, position, and level of play specificBoth aerobic and anaerobic

Endurance: ability to maintain optimal levels of strength, power and neuromuscular controlNeeds to be sport, position, and level of play specificBoth aerobic and anaerobic

Lower Extremity Endurance

Lower Extremity Endurance

Can be measured isokinetically (?)Aerobic vs Anaerobic conditioningMust be sport, position, and level specificNeeds to be performed within the context of the sport

Can be measured isokinetically (?)Aerobic vs Anaerobic conditioningMust be sport, position, and level specificNeeds to be performed within the context of the sport

Lower Extremity PowerLower Extremity Power

Power: the ability to exert maximal force in the shortest timeAbility to convert strength to movementFunctional/sport specific progression of strengthening exercisesIncludes plyometric training

Power: the ability to exert maximal force in the shortest timeAbility to convert strength to movementFunctional/sport specific progression of strengthening exercisesIncludes plyometric training

Plyometric TrainingPlyometric Training

Training of stretch shortening cycle of muscle actionGoals of Plyometrics• Improve explosive power• Tolerate greater stretch

loads• Attenuate ground reaction

forcesIsn’t a conditioning activity

Training of stretch shortening cycle of muscle actionGoals of Plyometrics• Improve explosive power• Tolerate greater stretch

loads• Attenuate ground reaction

forcesIsn’t a conditioning activity

Advanced Training Program ComponentsAdvanced Training

Program Components

Flexibility programDynamic Stabilization exercisesStrength programCore ProgramSpeed and Agility exercisesAnaerobic ConditioningAerobic Conditioning

Flexibility programDynamic Stabilization exercisesStrength programCore ProgramSpeed and Agility exercisesAnaerobic ConditioningAerobic Conditioning

Flexibility ProgramFlexibility ProgramShould include both static and dynamic stretchesLower extremity should focus on• Hamstrings• Quads• Gastroc/soleus• Hip flexor• Hip rotators• Illiotibial band

Should include both static and dynamic stretchesLower extremity should focus on• Hamstrings• Quads• Gastroc/soleus• Hip flexor• Hip rotators• Illiotibial band

Dynamic Stabilization Exercises

Dynamic Stabilization Exercises

Proprioceptive/ neuromuscular control exercises for the lower extremityShould include• Balance exercises (balance

boards, disc, etc)• Manual rhythmic

stabilization and PNF exercises

• Partner balance exercises (ball toss, manual perturbations)

Proprioceptive/ neuromuscular control exercises for the lower extremityShould include• Balance exercises (balance

boards, disc, etc)• Manual rhythmic

stabilization and PNF exercises

• Partner balance exercises (ball toss, manual perturbations)

Strength ProgramStrength Program

Should include both bilateral and unilateral exercisesThink sport and position specificEmphasize quad and hamstring exercises

Should include both bilateral and unilateral exercisesThink sport and position specificEmphasize quad and hamstring exercises

Core TrainingCore TrainingCore: Lumbar-pelvic-hip complexAll movement begins with the coreAccelerates, decelerates and dynamically stabilizes the bodyAllows the body to work as an integrated unitCan improve performance and prevent injury

Core: Lumbar-pelvic-hip complexAll movement begins with the coreAccelerates, decelerates and dynamically stabilizes the bodyAllows the body to work as an integrated unitCan improve performance and prevent injury

Core ProgramCore Program

Need to teach draw in maneuverIncorporate stabilization with all rehabilitation exercisesNot just “ab” workExamples• Bridging progression• Plank exercises• Reverse curl ups• Leg raises• Physioball exercises

Need to teach draw in maneuverIncorporate stabilization with all rehabilitation exercisesNot just “ab” workExamples• Bridging progression• Plank exercises• Reverse curl ups• Leg raises• Physioball exercises

Speed and Agility Exercises

Speed and Agility Exercises

Straight Ahead Speed• Includes acceleration, top

speed, speed endurance, deceleration

Lateral Speed and Agility• Includes acceleration, change

of direction, decelerationSpeed and agility exercises• Speed ladder• Resisted running• Assisted running• Change of direction drills

Straight Ahead Speed• Includes acceleration, top

speed, speed endurance, deceleration

Lateral Speed and Agility• Includes acceleration, change

of direction, decelerationSpeed and agility exercises• Speed ladder• Resisted running• Assisted running• Change of direction drills

Anaerobic ConditioningAnaerobic Conditioning

Interval trainingNeeds to be sport, position, and level of play specific• Frequency• Duration• Intensity • Distance

Interval trainingNeeds to be sport, position, and level of play specific• Frequency• Duration• Intensity • Distance

Aerobic ConditioningAerobic Conditioning

General Fitness BaseRecovery activityNeeds to be sport, position, and level of play specific

General Fitness BaseRecovery activityNeeds to be sport, position, and level of play specific

Return to PracticeReturn to Practice

Initiated in advanced training phaseSystematic return to full sport activatesNon-contact drillsFull contact drillsScrimmagesFull practice

Initiated in advanced training phaseSystematic return to full sport activatesNon-contact drillsFull contact drillsScrimmagesFull practice

Non-Contact PracticeNon-Contact Practice

Start with straight line drills Add sport specific inputProgress to change of direction drillsAdd sport specific inputNo symptoms and equal quality of movement and neuromuscular control side to side before progressing to non-contact scrimmages

Start with straight line drills Add sport specific inputProgress to change of direction drillsAdd sport specific inputNo symptoms and equal quality of movement and neuromuscular control side to side before progressing to non-contact scrimmages

Contact PracticeContact Practice

Must pass return to sport criteria before initiating contact drillsNo symptoms and equal quality of movement and neuromuscular control side to side before progressing to full practiceNeed coaches input to determine if the player is “back to where they were pre-injury”

Must pass return to sport criteria before initiating contact drillsNo symptoms and equal quality of movement and neuromuscular control side to side before progressing to full practiceNeed coaches input to determine if the player is “back to where they were pre-injury”

Return to Sport CriteriaReturn to Sport Criteria

Functional testing at 85% of uninvolvedIsokinetic testing at 85% of uninvolvedSatisfactory performance with sport specific testingMinimal symptoms with testing and no joint effusion

Functional testing at 85% of uninvolvedIsokinetic testing at 85% of uninvolvedSatisfactory performance with sport specific testingMinimal symptoms with testing and no joint effusion

Return to Full Game Status

Return to Full Game Status

Will already be participating in contact practiceEqual quality of movement and neuromuscular control side to sideMinimal symptoms and no joint effusionShould pass all team fitness criteriaShould have at least 2 full weeks of contact practice before playing

Will already be participating in contact practiceEqual quality of movement and neuromuscular control side to sideMinimal symptoms and no joint effusionShould pass all team fitness criteriaShould have at least 2 full weeks of contact practice before playing

Other ConsiderationsOther Considerations

Meniscal Repair• Avoid flexion past 90° in weight bearing for

first 6 weeks• Avoid pivoting/twisting with flexion in weight

bearing• Weight bearing as tolerated in full extension

for 3-4 weeks• Continue brace for first 6 weeks; limited to

90° of flexion with ambulation• Look to initiate running in 3-4 months

Meniscal Repair• Avoid flexion past 90° in weight bearing for

first 6 weeks• Avoid pivoting/twisting with flexion in weight

bearing• Weight bearing as tolerated in full extension

for 3-4 weeks• Continue brace for first 6 weeks; limited to

90° of flexion with ambulation• Look to initiate running in 3-4 months

Other ConsiderationsOther Considerations

Bone Bruise• Limit weight bearing early on• Good candidate for aquatic rehab

Chondral Lesion• Need to know what procedure if any was performed• If micro fracture procedure or osteochondral grafting

done, will be a restriction in their weight bearing status early on

• Need to limit shear forces

Bone Bruise• Limit weight bearing early on• Good candidate for aquatic rehab

Chondral Lesion• Need to know what procedure if any was performed• If micro fracture procedure or osteochondral grafting

done, will be a restriction in their weight bearing status early on

• Need to limit shear forces

ConclusionConclusionRehab based on objective findings and measurable goals versus time framesMake rehab sport/activity specificConsider biological healing times of concomitant procedures

Rehab based on objective findings and measurable goals versus time framesMake rehab sport/activity specificConsider biological healing times of concomitant procedures

Thank YouThank You

ReferencesReferencesBach BR Jr, Boonos CL: Anterior cruciate ligament reconstruction.AORN J. 2001 Aug;74(2):152-64Buss DD, Warren RF, Wickiewicz TL, Galinat BJ, and Panariello R: Arthroscopically assisted reconstruction of the anterior cruciate ligament with use of autogenous patellar-ligament grafts. Results after twenty-four to forty-two months J Bone Joint Surg Am 1993 75: 1346-1355. Fitzgerald GK: Open versus closed kinetic chain exercise: issues in rehabilitation after anterior cruciate ligament reconstructive surgery.Phys Ther. 1997 Dec;77(12):1747-54. Falconiero RP, DiStefano VJ, Cook TM: Revascularization and ligamentization of autogenous anterior cruciate ligament grafts in humans.Arthroscopy. 1998 Mar;14(2):197-205. Grontvedt T, Engebretsen L, Benum P, Fasting O, Molster A, Strand T: A prospective, randomized study of three operations for acute rupture of the anterior cruciate ligament. Five-year follow-up of one hundred and thirty-one patients.J Bone Joint Surg Am. 1996 Feb;78(2):159-68. Martin SD, Martin TL, Brown CH: Anterior cruciate ligament graft fixation.Orthop Clin North Am. 2002 Oct;33(4):685-96. McFarland, E: ACL Update: The Biology of Anterior Cruciate Ligament Reconstructions. Orthopedics 1993 April;16(4)

Bach BR Jr, Boonos CL: Anterior cruciate ligament reconstruction.AORN J. 2001 Aug;74(2):152-64Buss DD, Warren RF, Wickiewicz TL, Galinat BJ, and Panariello R: Arthroscopically assisted reconstruction of the anterior cruciate ligament with use of autogenous patellar-ligament grafts. Results after twenty-four to forty-two months J Bone Joint Surg Am 1993 75: 1346-1355. Fitzgerald GK: Open versus closed kinetic chain exercise: issues in rehabilitation after anterior cruciate ligament reconstructive surgery.Phys Ther. 1997 Dec;77(12):1747-54. Falconiero RP, DiStefano VJ, Cook TM: Revascularization and ligamentization of autogenous anterior cruciate ligament grafts in humans.Arthroscopy. 1998 Mar;14(2):197-205. Grontvedt T, Engebretsen L, Benum P, Fasting O, Molster A, Strand T: A prospective, randomized study of three operations for acute rupture of the anterior cruciate ligament. Five-year follow-up of one hundred and thirty-one patients.J Bone Joint Surg Am. 1996 Feb;78(2):159-68. Martin SD, Martin TL, Brown CH: Anterior cruciate ligament graft fixation.Orthop Clin North Am. 2002 Oct;33(4):685-96. McFarland, E: ACL Update: The Biology of Anterior Cruciate Ligament Reconstructions. Orthopedics 1993 April;16(4)

ReferencesReferencesRougraff B, Shelbourne KD, Gerth PK, Warner J: Arthroscopic and histologic analysis of human patellar tendon autografts used for anterior cruciate ligament reconstruction.Am J Sports Med. 1993 Mar-Apr;21(2):277-84. Scranton PE Jr, Lanzer WL, Ferguson MS, Kirkman TR, Pflaster DS:Mechanisms of anterior cruciate ligament neovascularization and ligamentization.Arthroscopy. 1998 Oct;14(7):702-16. Snyder-Mackler L, Delitto A, Stralka SW, Bailey SL: Use of electrical stimulation to enhance recovery of quadriceps femoris muscle force production in patients following anterior cruciate ligament reconstruction.Phys Ther. 1994 Oct;74(10):901-7.Shelbourne KD, Nitz P Accelerated rehabilitation after anterior cruciate ligament reconstruction.Am J Sports Med. 1990 May-Jun;18(3):292-9. PMID: 2372081 Wilk KE, Reinold MM, Hooks TR: Recent advances in the rehabilitation of isolated and combined anterior cruciate ligament injuries.Orthop Clin North Am. 2003 Jan;34(1):107-37

Rougraff B, Shelbourne KD, Gerth PK, Warner J: Arthroscopic and histologic analysis of human patellar tendon autografts used for anterior cruciate ligament reconstruction.Am J Sports Med. 1993 Mar-Apr;21(2):277-84. Scranton PE Jr, Lanzer WL, Ferguson MS, Kirkman TR, Pflaster DS:Mechanisms of anterior cruciate ligament neovascularization and ligamentization.Arthroscopy. 1998 Oct;14(7):702-16. Snyder-Mackler L, Delitto A, Stralka SW, Bailey SL: Use of electrical stimulation to enhance recovery of quadriceps femoris muscle force production in patients following anterior cruciate ligament reconstruction.Phys Ther. 1994 Oct;74(10):901-7.Shelbourne KD, Nitz P Accelerated rehabilitation after anterior cruciate ligament reconstruction.Am J Sports Med. 1990 May-Jun;18(3):292-9. PMID: 2372081 Wilk KE, Reinold MM, Hooks TR: Recent advances in the rehabilitation of isolated and combined anterior cruciate ligament injuries.Orthop Clin North Am. 2003 Jan;34(1):107-37