Rehabilitation After Anterior Cruciate Ligament Reconstruction: Criteria-Based Progression Through the Return-to-Sport Phase Gregory D. Myer, MS, CSCS 1 Mark V. Paterno, PT, MS, SCS, ATC 2 Kevin R. Ford, MS 3 Carmen E. Quatman, BS 4 Timothy E. Hewett, PhD 5 Rehabilitation following anterior cruciate ligament (ACL) reconstruction has undergone a relatively rapid and global evolution over the past 25 years. However, there is an absence of standardized, objective criteria to accurately assess an athlete���s ability to progress through the end stages of rehabilitation and safe return to sport. Return-to-sport rehabilitation, progressed by quantitatively measured functional goals, may improve the athlete���s integration back into sport participation. The purpose of the following clinical commentary is to introduce an example of a criteria-driven algorithm for progression through return-to-sport rehabilitation following ACL reconstruction. Our criteria-based protocol incorporates a dynamic assessment of baseline limb strength, patient- reported outcomes, functional knee stability, bilateral limb symmetry with functional tasks, postural control, power, endurance, agility, and technique with sport-specific tasks. Although this algorithm has limitations, it serves as a foundation to expand future evidence-based evaluation and to foster critical investigation into the development of objective measures to accurately determine readiness to safely return to sport following injury. J Orthop Sports Phys Ther 2006 36(6):385-402. doi:10.2519/jospt.2006.2222 Key Words: anterior cruciate ligament, knee rehabilitation, lower extremity, sport injury 1 Sports Biomechanist, Cincinnati Children���s Hospital Research Foundation, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, OH. 2 Coordinator of Orthopaedic and Sports Physical Therapy, Cincinnati Children���s Hospital Research Foundation, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, OH Coordinator of Orthopaedic and Sports Physical Therapy, Division of Occupational Therapy and Physical Therapy, Cincinnati Children���s Hospital Medical Center, Cincinnati, OH. 3 Research Biomechanist, Cincinnati Children���s Hospital Research Foundation, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, OH Doctoral Student, University of Kentucky, Department of Kinesiology and Health Promotion, Lexington, KY. 4 Research Assistant, Cincinnati Children���s Hospital Research Foundation, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, OH Medical Student, Medical University of Ohio, Center for Diabetes and Endocrine Research, Toledo, OH. 5 Director, Cincinnati Children���s Hospital Research Foundation, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, OH Associate Professor, University of Cincinnati College of Medicine, Departments of Pediatrics and Orthopaedic Surgery, Rehabilitation Sciences and Bioengineer- ing, College of Engineering, Cincinnati, OH. Address correspondence to Gregory D. Myer, Cincinnati Children���s Hospital, 3333 Burnet Avenue, MLC 10001, Cincinnati, OH 45229. E-mail: greg.myer@chmcc.org Atechniquesinand dvances fixation methods other graft reconstruction have dra- matically improved surgical success with anterior cruciate ligament (ACL) recon- struction.16,21 The advances in sur- gical technique have resulted in consistently good surgical out- comes and may shift the potential for an athlete to return to his or her previous level of sport, to be more determined by differences in rehabilitation than by surgical pro- cedure.16,44,45 Traditional ACL re- habilitation that once included prolonged immobilization, non- weight bearing and slow progres- sion to activity, now emphasizes immediate motion, early weight bearing and accelerated return to sports participation for athletic pa- tients. Compared to past protocols, rehabilitation programs are now more aggressive and advocate the release of athletes to sports activi- ties in as early as 8 weeks after surgery.82,83 Athlete return to play is often dictated by graft stability (anterior- posterior tibiofemoral motion), pa- tient confidence, postsurgical Journal of Orthopaedic & Sports Physical Therapy 385 C L I N I C A L C O M M E N T A R Y

timeline, and subjective medical team opinion. Ap- propriate objective criteria that consider both graft strength and objective functional criteria to deter- mine advancement through the end stages of reha- bilitation and readiness to return to sport following ACL reconstruction remain elusive.44 Rehabilitation and ultimate return to sport, using objective tests that quantitatively measure functional ability, may increase athlete reintegration to sports at the same competi- tive level as prior to the injury. Rehabilitation following ACL reconstruction is commonly divided into early (immediate postopera- tive and subacute strengthening) and late rehabilita- tion phases (functional progression and return to sport), with specific goals and time since surgery as determinants for phase progression. Early phases of post-ACL reconstruction often utilize stringent, criteria-based guidelines for range of motion (ROM) and progression to full weight bearing and exercise selection. In contrast, the final phases of rehabilita- tion prescriptions are typically broader, with general categorizations of appropriate exercises and progres- sions, without specific milestones for when it is safe to introduce high-risk and high���joint-loading activi- ties.83,88,89 In addition, more conservative therapeutic approaches may limit progression to later stages of rehabilitation and possibly delay successful return to sport. Exercise prescription for an athlete���s progression through rehabilitation and back-to-sport participation should avoid stretching the graft in athletes who do not possess the strength and functional abilities necessary to protect the healing joint while undertak- ing high���joint-loading activities. Structurally, animal studies indicate that the graft���s strength may reach its weakest point at approximately 6 to 8 weeks postop- eratively14 and may only reach failure loads between 11% and 50% of the native ACL at 1-year postopera- tive.5 Controlled loading may enhance ligament and tendon healing,3,4 while excessive loading can poten- tially damage the healing graft and lead to increased anterior-posterior knee laxity.9 Graft healing proper- ties have been studied primarily in animal models, including rabbits,5 canines,9 and primates.14 These types of animal models present important informa- tion related to histological properties, stiffness, and ultimate load to failure intermittently over a 1-year span in the mammal. However, the properties of a healing graft in animal models may be limited in their generalizability to outcomes in the human ACL.5,9,13, 14 The limited data in humans makes the determination of the optimal load to place on the healing ACL reconstruction, as well as the optimal timing to place that load, difficult to determine.8 It is possible to return to pivoting, twisting, and rotational sports as early as 3 to 4 months postoperatively 82,83 however, this early return to sport may not be safe for athletes who do not have sufficient functional stability to protect the weakened, healing graft. Healing ACL grafts may be better protected if more aggressive post-ACL reconstruction rehabilitation protocols were to utilize objective measures of functional status to drive rehabilitation progression. Progression should be based on variables that determine functional stability and neuromuscular control. This may im- prove successful early (2-3 months) return to sport and good long-term outcomes.76 Concomitant with decreased biomechanical strength of the ACL graft relative to the native ligament, athletes may demonstrate decreased muscu- lar strength, joint position sense, postural stability, and force attenuation (significant limb-to-limb land- ing ground reaction force differences during bilateral tasks) for 6 months to 2 years after reconstruc- tion.19,25,51,62,71 Deficits evident in the early stages of rehabilitation (unique to the patient and possibly to the graft type), if left unaddressed, will likely persist beyond the late rehabilitative stages.19,51 Ongoing biomechanical deficits that contribute to neuromus- cular performance during competitive sport may limit dynamic support, which may compromise the already weakened graft. This may increase the risk of ipsilateral ACL reinjury in the first year following reconstruction.68,78 In addition to reduced graft strength and altered functional joint control, there are other factors that make late-phase ACL rehabilitation a high-risk period for the athlete. During this phase of rehabilitation, clinicians must be especially cognizant of the poten- tial gap between the athlete���s perceived versus actual sports readiness, as subjective scores often do not correlate to quantified function and strength scores in patients with ACL injuries and reconstruc- tions.61,65,77 Without objective measures that identify potential deficits, it may be difficult for therapists to justify sport restriction and the associated limitations, as well as to address additional physical areas of concern. Specific progressive guidelines, based on objective measures, can provide a goal-oriented reha- bilitation process that may be an appealing approach for athletes.16 In summary, there is currently a lack of objective criteria to reliably determine how and when to progress a patient through end stage rehabilitation. The purpose of this clinical commentary is to intro- duce an example of a criteria-driven progression through the return-to-sport phase of rehabilitation following ACL reconstruction. The outlined progres- sion has yet to be validated however, both docu- mented and empirical evidence is provided for each component and the clinical rationale for the algo- rithm is outlined. The authors acknowledge that further validation is needed to formalize the use of 386 J Orthop Sports Phys Ther ��� Volume 36 ��� Number 6 ��� June 2006

our criteria-driven algorithm into the mainstream clinic, but we desire to utilize the current clinical commentary to initiate critical evaluation of our current practice. Criteria for Progression Into the Return-to-Sport Phase Our return-to-sport neuromuscular training incor- porates a progression through specific criteria de- signed to provide structure and objective standardization to late-phase rehabilitation following ACL reconstruction. Figure 1 presents an algorithmic flow chart used to track the athlete���s progress through the late rehabilitation stages. Prior to initia- tion of return-to-sport training, our recommendation is that the patient meets the following minimum baseline criteria: (1) minimum International Knee Documentation Committee (IKDC) Subjective Knee Form score of 70 (Appendix 1) (2) either no postsurgical history of giving way or a negative pivot shift and (3) a minimum baseline strength knee extension peak torque/body mass of at least 40% (male) and 30% (female) at 300��/s, and 60% (male) and 50% (female) at 180��/s. Carefully documented and validated subjective as- sessment of the patient���s ability to progress in reha- bilitation may be a key factor in determining an athlete���s readiness to enter a return-to-sport program. The International Knee Documentation Committee (IKDC) Subjective Knee Form is a reliable and valid tool for the determination of a patient���s rating of knee symptoms, function, and ability to participate in sport following knee injury���specifically, ACL injury36 (Appendix 1). The constructs validated for the IKDC were swelling, pain level, and functional ability. Initial scoring of at least 70 on the IKDC knee subjective rating form on the involved limb is one of the requirements for our athletes post-ACL reconstruc- tion to enter return-to-sport training. An IKDC rating of 69 or more would put athletes within 1 standard deviation of a population-based average for males and females aged 18 to 24 years (1079 limbs).2 Athletes with increased functional abilities may achieve an IKDC rating of 70 or greater and be prepared to progress into the return-to-sport phase more rapidly (2-4 months). An IKDC knee rating below 70 may indicate that an athlete is in need of additional recovery time from postsurgical trauma and improve- ment in functional status prior to beginning return to sport training. Incorporation of a validated subjective knee-rating system like the IKDC may bridge the gap between patient-perceived function and objectively measured function to enhance progress through the proposed algorithm in the return-to-sport phase of rehabilitation. Functional stability, or the ability to avoid giving way of the knee using dynamic muscular restraints, protects the healing graft following ACL reconstruc- tion. Though mechanical stability may be restored via surgical reconstruction, the patient may continue to experience functional instability (giving-way episodes or perceived instability) or functional impair- ments.34,80,85 Return to high-level sports is a high-risk period for athletes during the first year postrecon- struction.68,78,87 Return of a patient to high-level sports before functional stability is achieved may increase the potential for poor outcome. In addition, inadequate functional stability may be related to decreased confidence in the injured knee and to decreased ability to return to preinjury sports partici- pation.45 The inability of the patient to develop dynamic muscular joint stabilization through neuromuscular control during walking and activities of daily living (ADL) should exclude the patient from progression into an aggressive return-to-sport rehabili- tation phase.6,66 Therefore, the athlete should have no giving-way episodes prior to entering the return- to-sport phase. However, a giving-way episode may represent a deficiency in active (neuromuscular re- straint) or passive (static restraint) stability or a combination of both. A positive pivot shift indicates mechanical instability and is related to subjective reports of poor functional outcome.43,46 A patient who reports a previous history of giving-way episodes and a negative pivot shift likely possesses sufficient mechanical stability to safely enter into advanced rehabilitation exercises designed to address the func- tional instability.38 Measurable functional deficits that may relate to past giving-way episodes may be correct- able if the athlete participates in safe and progressive return-to-sport training. Prior to initiation of return-to-sport training, the athlete should demonstrate sufficient strength to improve potential for success.48 The absence of sufficient strength may result in an inability to initiate dynamic movements, to attenuate ground reaction forces, or to achieve high levels of performance during dynamic tasks.41,48 Normative ranges for postpubescent adolescents and adults for isokinetic knee extension peak torque-body mass ratio at 300��/s are 40% to 55% for men and 30% to 45% for women, and at 180��/s are 58% to 75% for men and 50% to 65% for women.10 We use a minimum quadriceps torque-body mass ratio of 40% for males and 30% for females at 300��/s, and 60% for males and 50% for females at 180��/s, for return-to-sport training for the athletic population. These values are the low ranges of normative data that we hypothesize are the baseline levels of strength that athletes should demonstrate for a safe and successful introduction into the initial stages of the return-to-sport program. J Orthop Sports Phys Ther ��� Volume 36 ��� Number 6 ��� June 2006 387 C L I N I C A L C O M M E N T A R Y