PhD Pinboard: Advancing On-Field Rehabilitation after ACL Injury
- Jo Clubb
- 8 minutes ago
- 13 min read
This PhD Pinboard article by Filippo Picinini explores on-field rehabilitation, workload monitoring, and return-to-play outcomes in ACL-reconstructed football players.
My name is Filippo Picinini, and I am a passionate and resilient Rehab and Performance coach who integrates my expertise as a strength and conditioning, rehabilitation, and physical performance specialist. I am employed full-time as Head of late-stage rehabilitation and Sports Science at Isokinetic Medical Group London, while I pursue my PhD at St Mary’s University, Twickenham.
My doctoral research builds on a long-standing line of work developed within the Isokinetic Education & Research Department, and focuses on one of the most critical challenges in football medicine: how we return players to the same pre-injury level of football after an Anterior cruciate ligament (ACL) injury with surgical reconstruction (ACLR).
Although my personal journey into this field began on the pitch—working daily with professional and amateur ACLR players—the conceptual foundations of this research trace back several years. The framework for on-field rehabilitation (OFR), the recognition of theoretical gaps, and the need for structured research in this area were initially identified and developed collectively by the Isokinetic Education & Research Department, established in 2000 by Dr. Stefano Della Villa, M.D., and currently led by Dr. Francesco Della Villa, M.D., with the scientific support from Dr. Matthew Buckthorpe, PhD, and, with important contributions during earlier stages from Matteo Parigino. My PhD represents the continuation and expansion of this programme, advancing the department’s long-term objective of generating robust scientific evidence to support ACL rehabilitation and the return-to-play (RTP) process.
Working clinically, I often questioned whether we were truly preparing players for the realities of football. Strength tests improve indoor, gym-based exercises are ticked off, but once players return to the pitch, the demands change dramatically. Football is chaotic, multidirectional, and physically intense. The gap between what we measure and what players experience outdoors is an issue that our department has been discussing for years.
Further, when we examined the literature, it was evident that despite extensive knowledge on early- and mid-stage rehabilitation, the OFR phase remained poorly documented. Existing publications were mostly single-case studies, commentary papers, or conceptual frameworks—highlighting a need for quantitative evidence. These reflections influenced the development of our current OFR-ACL research programme, and my doctoral projects aim to advance this established agenda, contributing new data to address longstanding evidence gaps.
Why does this research matter?
Every year, ACL injuries take players out of the game for months, sometimes more than a year (1). Despite advances in surgery and rehabilitation (2), too many athletes struggle to return to their previous level—or suffer a re-injury shortly after stepping back on the pitch (3). In professional football, around one in five male players will sustain a knee re-injury within two years of returning (4). For female and younger players, the risk can be as high as one in three (5,6).
Returning a football player to sport after an ACL injury with surgical reconstruction requires a criteria-based rehabilitation plan characterised by multiple rehabilitation stages on a timeline ranging between 6 and 12 months (7,2). While we’ve made progress in understanding ACL injury mechanisms and situational patterns (8,9), there’s a clear gap in evidence around the later stages of rehabilitation—especially when players transition from the gym-based environment back to the pitch and then with the team in training (10–14).
The on-field rehabilitation phase is crucial, as it acts as a bridge between gym-based rehabilitation and the competitive team environment (15). It strives to be an optimal rehabilitation environment to minimise the differences in workload that the athlete can experience during the RTP process (16,17).
Despite clear benefits in completing a period of OFR before returning to sport (18–20,4), evidence documenting optimal OFR workloads to progress ACLR players to the team in training safely is lacking, and the effectiveness of this rehabilitation phase across the return to sport (RTS) continuum hasn’t been defined yet (21).
Our ambition, as the Isokinetic Education & Research Department, is to shed more light on this topic via my PhD programme. Across four studies, we are investigating how OFR is administered in football settings, how much workload players accumulate during this phase, and whether completing a structured OFR programme influences RTP outcomes and ACL re-injury risk.
PhD Structure and Key Findings
We started by mapping the field. A survey conducted by Armitage et al., 2024 in English professional football has reported information on who is responsible for delivering OFR in a football club and which evidence they use, drill choices, progressions, and OFR monitoring tools (21). Despite more clarity around OFR practices in professional football clubs, evidence documenting the optimal amount of time, OFR sessions and workloads that ACLR football players are recommended to complete during a period of OFR and before returning to the team in training remains anecdotal (17).
Through an international survey, which is currently underway, involving physiotherapists, strength and conditioning coaches, and other practitioners who deliver the OFR phase in a professional football club setting, we are collecting information on how OFR is administered and incorporated into the RTP process for players returning to competitive 11-a-side football post-ACLR. The questions implemented in the survey will bring light to the following areas of the OFR and RTP process:
OFR frameworks used, clinical experience in planning and delivering OFR sessions and progression strategies
Workload management during the OFR phase and technologies used to monitor internal and external workloads, with specific emphasis on the use of the GPS technology in monitoring and benchmarking players during the RTP process
Approach to transition ACLR players to the team in training and GPS-based thresholds typically used to determine whether the player is ready for the transition.
Retrospective Analysis of Return to Play
The second study forms part of the broader departmental objective to quantify the value of OFR within the RTP continuum, building on conceptual work conducted in earlier project phases (19). We designed this study to investigate the impact of OFR on RTP and 2nd ACL injury risk in ACLR football players. It was hypothesised that players completing more OFR sessions would show i) a higher RTP rate at the same level and ii) a lower 2nd ACL injury rate compared to the current literature.
Data from 401 male football players who underwent primary ACLR between 2010 and 2014 were retrospectively analysed. All players took part in a standardised rehabilitation protocol, involving a period of OFR. Participants were stratified by competitive level (professionals and amateurs), and between-group differences in RTP and re-injury outcomes were documented. The predictive value of OFR volume (overall number of sessions completed before RTP) and weekly frequency for each outcome was assessed using logistic regressions, controlling for competitive level.
Eighty-four percent of players returned to their pre-injury competitive level, with professionals (88%) and amateurs (83%) returning in 5.9 ± 2.1 and 6.9 ± 3.2 months, respectively. Greater OFR volume (OR, 1.06; 95% CI, 1.00–1.12; p = 0.034) and OFR weekly frequency (OR, 1.53; 95% CI, 1.00–1.07; p = 0.014) were associated with increased RTP likelihood. High compliance in OFR (volume and frequency) increased RTP probability by more than 2.5 times (OR=2.62, p=0.003) with a combined RTP of 91% of the players.
We identified an OFR volume of ≥24 sessions completed as predictive for professional players returning to the same pre-injury level of football, whereas the cut-off for amateurs was ≥11.
Forty-two players (10%) sustained a 2nd ACL injury, of which 20 were ipsilateral and 22 contralateral. No professional reported an ipsilateral re-injury. OFR variables were not significantly associated with 2nd ACL injury; however, compliance in OFR reduced the likelihood of sustaining an ipsilateral re-injury by 77% (OR=0.23, p=0.041) in young players <20 years old.
Incorporating Physical Workloads
A significant contribution from our Isokinetic Education & Research Department was updating our OFR approach, which now consists of four key pillars (Figure 1) (15), incorporating the use of GPS technology to monitor our players during this phase. The current OFR framework served as the foundation for designing the workload studies included in my PhD.
My contribution, via the third and fourth prospective cohort study, was to zoom in on the workloads players accumulate during our 5-staged OFR programme to advance the anecdotal evidence base supporting this framework. (Figure 2) (17).
We wanted to investigate how much workload ACLR 11-a-side male footballers, competing at different levels (professional vs. amateur), complete following an indoor criteria-based rehabilitation process, and before being cleared to RTP. Ultimately, we were determined to understand if there are differences among levels of play (professional versus amateurs) and if the load can act as a moderator in increasing the RTS rate and decreasing the risk of re-injury.
The project is still underway, but we have published some preliminary findings. We found that professionals completed more OFR sessions (20.6±7.7 vs. 13.2±7.7, p<0.001) over a shorter period (44.7±30.3 vs. 59.3±28.5 days, p=0.044) compared to amateurs, and achieved higher workloads mostly in the high-speed GPS metrics at each OFR stage.
External running loads progressed over the course of the 5-staged OFR program, and those players who completed it by reaching Stage 5 effectively restored the total distance and the high-speed running demands necessary for team training. Acceleration and deceleration distances and peak running speeds achieved in stage 5 remained sub-optimal with respect to football team training demands (TD: 106%, HID: 104%, PS: 88%, ACC: 110%, DEC: 48%). All metrics were low in relation to match play demands (TD: 44%, HID: 51%, PS: 82%, ACC: 63%, DEC: 26%), corroborating OFR as a rehabilitation phase that prepares for reintegration for team training, but not match play (Figure 3).
After completing the data collection, the final step is to investigate if the workload accumulated during a period of OFR can act as a moderator in increasing the RTP rate and decreasing the risk of ACL re-injury. Our hypothesis is that completing more workloads during a period of OFR leads to improved RTP outcomes and reduced risk of re-injury in ACLR 11-a-side football players. Specifically, we are keen to understand if a certain type of workload quantified by different GPS metrics (e.g., accelerations/decelerations, high-speed running, etc.) is more predictive of RTP and 2nd ACL injury.
How can we apply these findings in practice?
Several RTP frameworks have been published (16,23,24), but the role and value of the on-field rehabilitation phase remain unclear in the ACL rehabilitation journey and RTS continuum (21). Information on OFR activities and workloads completed by large cohorts of ACLR football players, published during my PhD journey, with data presented according to level of play, will support practitioners operating in both professional and amateur football by providing more evidence to complement published single case studies, anecdotal frameworks, and clinical experience.
Ultimately, we want to provide practitioners with clearer evidence and benchmarks to guide decision-making in this critical stage of the recovery process, to safely progress their ACL-reconstructed players across the on-field rehabilitation phase and towards return to competitive match play, with a lower risk of re-injury.
Final Thoughts
The burden of ACL injuries in football remains high due to prolonged recovery, significant player time lost, and high financial costs for the club (25). Returning to play after an ACL injury in football requires a complex, criteria-based approach, often accompanied by high pressure and limited time available, and no gold standard pathway exists to rehab this injury (26,27).
Although my PhD studies investigate substantial datasets comprising homogeneous groups of male ACLR football players—both professional and amateur—it's important to remember that players are individuals. Rehabilitation protocols must be thorough and personalised, progress should depend on players’ responses to gradual and appropriate loading, and multidisciplinary collaboration is essential for successful rehabilitation.
The findings emerging from my PhD belong to the broader work of our Isokinetic Education & Research Department, whose long-term commitment to ACL rehabilitation research has enabled a unique, structured, and internationally relevant programme of study.
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Frequently Asked Questions (FAQ)
What is on-field rehabilitation (OFR) in the context of ACL reconstruction?
On-field rehabilitation is a structured, criteria-based phase that follows gym-based rehabilitation and precedes full team training. Its purpose is to progressively reintroduce football-specific movement patterns, physical loads, and technical demands in a controlled environment. Current evidence indicates that structured OFR completion is associated with improved return-to-play outcomes at the same competitive level.
Can on-field rehabilitation workloads be used as predictors of return-to-play outcomes?
Emerging evidence suggests that greater exposure to OFR—both in terms of session volume and weekly frequency—is associated with a higher likelihood of returning to the same pre-injury level. Thresholds appear to differ by competitive level, highlighting the importance of context-specific benchmarks. Ongoing work is investigating whether specific workload components (GPS variables) act as stronger predictors.
Why are acceleration and deceleration demands still limited at the end of on-field rehabilitation?
Despite progression through advanced OFR stages, acceleration and deceleration loads remain substantially lower than those observed in team training and match play. This likely reflects the need to balance tissue protection with progressive overload. These findings also suggest that ACL-reconstructed players may require greater OFR exposure to adequately restore acceleration–deceleration demands, identifying a potential target for future optimisation.
Does successful completion of on-field rehabilitation equate to readiness for match play?
OFR is designed to prepare players for reintegration into team training rather than direct return to competition. Even at advanced OFR stages, workloads typically remain below match-play demands, underscoring the need for a progressive return-to-competition strategy.
References
1. Ardern CL, Webster KE, Taylor NF, Feller JA. Return to sport following anterior cruciate ligament reconstruction surgery: a systematic review and meta-analysis of the state of play. Br J Sports Med. 2011 Jun;45(7):596–606.
2. Mayer MA, Deliso M, Hong IS, Saltzman BM, Longobardi RS, DeLuca PF, et al. Rehabilitation and Return to Play Protocols After Anterior Cruciate Ligament Reconstruction in Soccer Players: A Systematic Review. Am J Sports Med. 2024 Apr 15;3635465241233161.
3. Waldén M, Hägglund M, Magnusson H, Ekstrand J. ACL injuries in men’s professional football: a 15-year prospective study on time trends and return-to-play rates reveals only 65% of players still play at the top level 3 years after ACL rupture. Br J Sports Med. 2016 Jun;50(12):744–50.
4. Della Villa F, Hägglund M, Della Villa S, Ekstrand J, Waldén M. High rate of second ACL injury following ACL reconstruction in male professional footballers: an updated longitudinal analysis from 118 players in the UEFA Elite Club Injury Study. Br J Sports Med. 2021 Dec;55(23):1350–6.
5. Webster KE, Feller JA. Exploring the High Reinjury Rate in Younger Patients Undergoing Anterior Cruciate Ligament Reconstruction. Am J Sports Med. 2016 Nov;44(11):2827–32.
6. Webster KE. Return to Sport and Reinjury Rates in Elite Female Athletes After Anterior Cruciate Ligament Rupture. Sports Med [Internet]. 2021 Apr 1 [cited 2025 Dec 10];51(4):653–60. Available from: https://doi.org/10.1007/s40279-020-01404-7
7. van Melick N, van Cingel REH, Brooijmans F, Neeter C, van Tienen T, Hullegie W, et al. Evidence-based clinical practice update: practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus. Br J Sports Med. 2016 Dec;50(24):1506–15.
8. Della Villa F, Buckthorpe M, Grassi A, Nabiuzzi A, Tosarelli F, Zaffagnini S, et al. Systematic video analysis of ACL injuries in professional male football (soccer): injury mechanisms, situational patterns and biomechanics study on 134 consecutive cases. Br J Sports Med. 2020 Dec;54(23):1423–32.
9. Lucarno S, Zago M, Buckthorpe M, Grassi A, Tosarelli F, Smith R, et al. Systematic Video Analysis of Anterior Cruciate Ligament Injuries in Professional Female Soccer Players. Am J Sports Med. 2021 Jun;49(7):1794–802.
10. Wright RW, Haas AK, Anderson J, Calabrese G, Cavanaugh J, Hewett TE, et al. Anterior Cruciate Ligament Reconstruction Rehabilitation: MOON Guidelines. Sports Health. 2015 May;7(3):239–43.
11. Schwellnus M, Soligard T, Alonso JM, Bahr R, Clarsen B, Dijkstra HP, et al. How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness. Br J Sports Med. 2016 Sep;50(17):1043–52.
12. Soligard T, Schwellnus M, Alonso JM, Bahr R, Clarsen B, Dijkstra HP, et al. How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury. Br J Sports Med. 2016 Sep;50(17):1030–41.
13. Andrade R, Pereira R, van Cingel R, Staal JB, Espregueira-Mendes J. How should clinicians rehabilitate patients after ACL reconstruction? A systematic review of clinical practice guidelines (CPGs) with a focus on quality appraisal (AGREE II). Br J Sports Med. 2020 May;54(9):512–9.
14. Rambaud AJ, Neri T, Dingenen B, Parker D, Servien E, Gokeler A, et al. The modifying factors that help improve anterior cruciate ligament reconstruction rehabilitation: A narrative review. Ann Phys Rehabil Med. 2022 Jun;65(4):101601.
15. Buckthorpe M, Della Villa F, Della Villa S, Roi GS. On-field Rehabilitation Part 1: 4 Pillars of High-Quality On-field Rehabilitation Are Restoring Movement Quality, Physical Conditioning, Restoring Sport-Specific Skills, and Progressively Developing Chronic Training Load. J Orthop Sports Phys Ther. 2019 Aug;49(8):565–9.
16. Buckthorpe M, Frizziero A, Roi GS. Update on functional recovery process for the injured athlete: return to sport continuum redefined. Br J Sports Med [Internet]. 2019 Mar 1 [cited 2024 Sep 4];53(5):265–7. Available from: https://bjsm.bmj.com/content/53/5/265
17. Buckthorpe M, Della Villa F, Della Villa S, Roi GS. On-field Rehabilitation Part 2: A 5-Stage Program for the Soccer Player Focused on Linear Movements, Multidirectional Movements, Soccer-Specific Skills, Soccer-Specific Movements, and Modified Practice. J Orthop Sports Phys Ther [Internet]. 2019 Aug [cited 2024 Sep 4];49(8):570–5. Available from: https://www.jospt.org/doi/10.2519/jospt.2019.8952
18. Roi GS, Creta D, Nanni G, Marcacci M, Zaffagnini S, Snyder-Mackler L. Return to official Italian First Division soccer games within 90 days after anterior cruciate ligament reconstruction: a case report. J Orthop Sports Phys Ther. 2005 Feb;35(2):52–61; discussion 61-66.
19. Della Villa S, Boldrini L, Ricci M, Danelon F, Snyder-Mackler L, Nanni G, et al. Clinical Outcomes and Return-to-Sports Participation of 50 Soccer Players After Anterior Cruciate Ligament Reconstruction Through a Sport-Specific Rehabilitation Protocol. Sports Health. 2012 Jan;4(1):17–24.
20. DELLA VILLA F, RICCI M, PERDISA F, FILARDO G, GAMBERINI J, CAMINATI D, et al. Anterior cruciate ligament reconstruction and rehabilitation: predictors of functional outcome. Joints [Internet]. 2016 Jan 31 [cited 2024 Sep 5];3(4):179–85. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4739537/
21. Armitage M, McErlain-Naylor SA, Devereux G, Beato M, Buckthorpe M. On-field rehabilitation in football: Current knowledge, applications and future directions. Front Sports Act Living. 2022;4:970152.
22. Armitage M, McErlain-Naylor SA, Devereux G, Beato M, Iga J, McRobert A, et al. On-field rehabilitation in football: current practice and perceptions. A survey of the English Premier League and Football League. Sci Med Footb. 2024 Mar 8;1–10.
23. Taberner M, Allen T, Cohen DD. Progressing rehabilitation after injury: consider the ‘control-chaos continuum’. Br J Sports Med. 2019 Sep;53(18):1132–6.
24. Mitchell A, Gimpel M. A Return-to-Performance Pathway for Professional Soccer: A Criteria-based Approach to Return Injured Professional Players Back to Performance. JOSPT Open [Internet]. 2024 Jul [cited 2024 Sep 4];2(3):166–78. Available from: https://www.jospt.org/doi/10.2519/josptopen.2024.1240
25. Bahr R, Clarsen B, Ekstrand J. Why we should focus on the burden of injuries and illnesses, not just their incidence. Br J Sports Med [Internet]. 2018 Aug 1 [cited 2025 Oct 7];52(16):1018–21. Available from: https://bjsm.bmj.com/content/52/16/1018
26. Ardern CL, Glasgow P, Schneiders A, Witvrouw E, Clarsen B, Cools A, et al. 2016 Consensus statement on return to sport from the First World Congress in Sports Physical Therapy, Bern. Br J Sports Med. 2016 Jul;50(14):853–64.
27. Dingenen B, Gokeler A. Optimization of the Return-to-Sport Paradigm After Anterior Cruciate Ligament Reconstruction: A Critical Step Back to Move Forward. Sports Med Auckl NZ. 2017 Aug;47(8):1487–500.
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