 
 
Rehabilitation Protocol for ACI Trochlea Patella 
  
This protocol is intended to guide clinicians through the post-operative course for Trochlea Patella Autologous 
Chondrocyte Implantation (ACI), a surgical procedure for the treatment of full thickness chondral lesions of the knee 
joint. The first stage is an arthroscopic procedure in which a sample of healthy cartilage is harvested from a non-weight 
bearing surface of the knee joint.  These cartilage cells are preserved and cultivated onto a scaffolding which is sized 
according to the individual's defect. The second stage (performed openly 3-5 weeks later) involves the implantation of 
these cartilage cells / scaffolding into the defect and sealed with fibrin glue.  The cells grow / mature to eventually form 
hard cartilage tissue over the next 24 months. Overall, the phases of the protocol are based on the 4 stages of cartilage 
maturation:  Proliferation, Transition, Remodeling, Maturation. The size and location of an individual’s defect guides the 
rehabilitation progression and may change the duration of the phases. Specific intervention should be based on the 
needs of the individual and should consider exam findings and clinical decision making. The timeframes for expected 
outcomes contained within this guideline may vary based on surgeon’s preference, additional procedures performed, 
and/or complications. If a clinician requires assistance in the progression of a post-operative patient, they should consult 
with the referring surgeon. 
  
The interventions included within this protocol are not intended to be an inclusive list of exercises. Therapeutic 
interventions should be included and modified based on the progress of the patient and under the discretion of the 
clinician.  
 
Considerations for the Post-operative ACI Trochlea Patella 
Many different factors influence the post-operative ACI Trochlea Patella rehabilitation outcomes, including the origin, 
size, and location of the defect as well as concomitant injury. Additional procedures may include a tibial tubercle 
osteotomy.  
 
PHASE I: IMMEDIATE POST-OP (Day 0 - 6 WEEKS AFTER SURGERY) 
Rehabilitation 
Goals 
• Protect healing graft / tissue (joint surface & wound)   
• Decrease knee / lower extremity (LE) swelling   
• Enhance volitional control of quad  
• Achieve full knee extension 
• Gradually restore knee flexion range of motion (ROM)   
• Restore patellofemoral joint mobility  
Weightbearing 
Status/ Brace / 
Things to Avoid 
Precautions:  
• Weeks 0-2: passive range of motion (PROM) only, limited knee flexion 0-40 degrees 
• No active knee extension from 40-70 degrees  
• No repetitive closed chain knee flexion from 40-70 degrees 
• Avoid forceful motion into pain (some mild pain with passive extension is acceptable) 
 
Weight Bearing:  
• Tibial Tubercle Osteotomy:  
- Touch down weightbearing in locked brace 
• No Osteotomy:  
- Immediately post-op: 25% weightbearing in locked knee brace 
- Week 2: progress to 50% weightbearing in locked knee brace 
- Weeks 3-4: progress to 75% weightbearing in locked knee brace 
- Weeks 5-6: progress to weightbearing as tolerated in unlocked knee brace 
Brace:  
• Locked at 0 degrees for ambulation and at night 
 
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• Removed for continuous passive motion / exercises 
• May lie in supine without brace in 0 degrees extension, if in safe protected position 
• Gradually open up brace with WB as quad control improves 
• Weeks 4-6: unlock to 20-30 degrees with ambulation if able to perform SLR without lag 
• Can discharge brace at 6 weeks if SLR without lag 
Interventions  
Pain/Effusion Management:  
• Electrical stimulation for quadriceps  
• Ice, compression, elevation (check with MD: cold therapy) 
• Retrograde effleurage  
• Ankle pumps 
 
Joint Mobilization: 
• Grade III superior and inferior patellofemoral joint (PFJ) mobilization (should be painfree) 
 
ROM:    
• PROM by therapist  
- Weeks 0-2: 0-40 degrees only 
- Weeks 2-6: gradually increase per patient tolerance 
 
Continuous Passive Motion (CPM): 
• Limit 0-40 degrees for Weeks 0-2, then increase CPM range by 5-10 degrees per day based on 
tolerance  
• CPM 6-8 hours/day in 2 hour blocks 
• Start 1 cycle per minute at full extension to a knee flexion angle that is comfortable. Advance as 
tolerated 
 
Therapeutic Exercise:  
• Heel prop  
• Seated knee flexion AAROM (limit 0-40 degrees Weeks 0-2) 
• Heel slides 
• Supine knee flexion (limit 0-40 degrees Weeks 0-2) 
• Quad sets 
• Hamstring isometrics 
• Straight leg raise (SLR) 
• Sidelying hip abduction 
• Stationary bike with elevated seat height(start at Week 4 only if patient has 90 degrees knee 
flexion) 
 
Additional Interventions: 
• Biofeedback for quad/VMO control 
• Blood Flow Restriction Therapy (BFRT) with quad set and SLR 
• Pool walking – axilla/chest deep (begin at Week 4 if incision is fully healed)  
- Chest deep (25% body weight)  
- Waist deep (50% body weight) 
Criteria to 
Progress 
• SLR with no lag (without brace) 
• Full passive knee extension 
• Knee flexion – 90 degrees by Week 4, >120 degrees by Week 6 
• Normal patellofemoral mobility  
• Controlled swelling 
 
PHASE II: INTERMEDIATE POST-OP (6 – 12 WEEKS AFTER SURGERY) 
Rehabilitation 
Goals 
• Protect healing graft 
• Achieve full knee flexion  
• Return to full weightbearing with normalized gait pattern 
• Progress quad strength and lower extremity control  
 
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Weightbearing 
Status / 
Precautions 
Precautions:  
• No active open chain knee extension from 40-70 degrees 
• Avoid repetitive closed chain knee flexion from 40-70 degrees 
• Avoid significant/persistent pain during or after exercise  
 
Weight Bearing:    
At 6 weeks, progress weight bearing as tolerated to full weight bearing by Weeks 8-9 
Additional 
Intervention 
*Continue with 
Phase I 
interventions as 
indicated 
Therapeutic Exercise: 
*ensure proper dynamic control with all exercises to avoid excessive shear on joint 
 
*all exercises below should be limited to ROM from 0-40 degrees knee flexion 
• Short arc knee extension (may begin at Week 9) 
• Standing heel raise 
• Bridging 
• Terminal knee extension  
• Mini squats  
• Wall slides  
• Step ups 
• Lateral step down  
• Resisted side stepping (band at thighs)  
 
Balance/Proprioception Exercise:  
• Single leg balance: begin at Week 8 
- Static – shoes on / eyes open 
- Varied surface  
- Vision – eye / head movements, eyes closed 
- Task (throw and catch)  
• Single leg balance with lower extremity swings 
• Single leg balance with upper extremity reach: Begin at Week 10 
 
Aerobic Exercise: 
• Stationary bike (no/minimal resistance for emphasis on range of motion) 
• Treadmill walking 
• Aquatic flutter or straight leg kicks with kickboard 
Criteria to 
Progress 
• Full knee ROM 
• Minimal/no swelling at baseline 
• Normal gait mechanics 
• Pain-free sit to stand  
 
PHASE III: LATE POST-OP (12 – 24 WEEKS AFTER SURGERY) 
Rehabilitation 
Goals 
• Protect healing graft 
• Progress single leg strength, control, and load tolerance 
• Progress balance/proprioception work in all 3 planes of motion  
Precautions  
Precautions: 
• Significant pain during activity 
• Significant swelling after activity 
• Post activity soreness > 24 hours 
• No active knee extension from 40-70 degrees 
Avoid repetitive closed chain knee flexion from 40-70 degrees 
Additional 
Intervention 
*Continue with 
Phase I-II 
Interventions as 
indicated 
Therapeutic Exercise:  
• Single leg dead lift 
• Leg press <40 degrees flexion 
• Single leg squat  <40 degrees flexion 
• Seated hamstring curl machine 
• Standing resisted knee flexion 
 
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• Double leg mini squat 
• SLR with weight 
• Small step up with weight if appropriate 
 
Balance/Proprioception Exercise:  
• Progress single leg balance with lower extremity reaching and perturbations 
 
Aerobic Exercise: 
• Treadmill forward and retro walking 
• Aquatics: flutter kicking (no whip kicks) and aqua jogging 
Criteria to 
Progress 
• Bilateral squat to 40 degrees flexion with good mechanics without pain 
• Single leg squat depth to at least 40 degrees knee flexion with good control without pain 
• All activities of daily living (ADLs) performed without pain or swelling 
 
PHASE IV: ADVANCED STRENGTHENING (24+ WEEKS AFTER SURGERY) 
Rehabilitation 
Goals 
• Progress active knee flexion in full range of motion 
• Hamstring and calf strength within 80% of the contralateral limb 
• Ability to ambulate long distance (5-10 km) without pain 
• Ability to effectively negotiate uneven terrain 
• Return to pre-operative low-impact recreational activities 
Additional 
Intervention 
• Progression of phase II-III exercises incorporating increased knee flexion (now permitted to 
perform knee flexion 40-70 degrees) 
Criteria to 
Progress 
• No effusion/pain after exercise 
• Return to low-impact recreational activities without pain or swelling 
• Ability to perform bilateral and single leg squat in increased range of motion with good control 
without pain 
 
PHASE V: EARLY RETURN TO SPORT (9-12 MONTHS AFTER SURGERY) 
Rehabilitation 
Goals 
• Quadriceps strength within 90% of the contralateral limb 
• Ability to perform all activities of daily living pain free 
• Initiate return to running program 
Additional 
Intervention 
*Continue with 
Phase II-IV 
interventions as 
indicated 
• Begin sub-maximal sport-specific training in the sagittal plane 
• Interval running Program 
-  Return to Running Program 
• Progress to plyometric and agility program 
- Agility and Plyometric Program 
Criteria to 
Progress 
• Clearance from MD and ALL milestone criteria have been met 
• Completion of jog/run program without pain/effusion/swelling 
• Functional Assessment: 
- Quadricep/hamstring/glute index >90% HHD mean or isokinetic testing at 60 
degrees/second 
- Hamstring/quad ratio >66% 
- Hop testing >90% compared to contralateral side, demonstrating good landing 
mechanics 
 
PHASE VI: UNRESTRICTED RETURN TO SPORT (12 MONTHS AFTER SURGERY) 
Rehabilitation 
Goals 
• Continue strengthening and proprioceptive exercises 
• Symmetrical performance with sport-specific drills 
• Safely progress to full sport 
Additional 
Intervention 
*Continue with 
Phase II-V 
• Multi-plane sport-specific plyometrics program 
• Multi-plane sport-specific agility program 
• Include hard cutting and pivoting depending on the individuals’ goals 
• Non-contact practice → full practice → full play 
 
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interventions as 
indicated 
Criteria to 
Progress 
• Functional Assessment: 
- Quadricep/hamstring/glute index >90% HHD mean or isokinetic testing at 60 
degrees/second 
- Hamstring/quad ratio >66% 
- Hop testing >90% compared to contralateral side, demonstrating good landing 
mechanics 
• KOOS-sports questionnaire > 90%  
• International Knee Committee Subjective Knee Evaluation > 93 
   Revised 12/2022 
 
Contact 
Please email MGHSportsPhysicalTherapy@partners.org with questions specific to this protocol 
