1998 Basmajian Student Award Paper: Movement patterns after anterior cruciate ligament injury: a comparison of patients who compensate well for the injury and those who require operative stabilization

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Abstract

The purpose of this study was to describe kinematic and kinetic differences between a group of ACL deficient subjects who were grouped according to functional ability. Sixteen patients with complete ACL rupture were studied; eight subjects had instability with activities of daily living (non-copers) and eight subjects had returned to all pre-injury activity without limitation (copers). Three-dimensional joint kinematics and kinetics were collected from the knee and ankle during walking, jogging and going up and over a step. Results showed that both groups mitigated the force with which they contacted the floor but non-copers consistently demonstrated less knee flexion in the involved limb. The copers used joint kinematics similar to those of their uninvolved knees and similar to knee motions reported in uninjured subjects. The reduced knee motion in the involved knee of the non-copers did not correlate directly with quadriceps femoris muscle weakness.

The data suggest that the non-copers utilize a stabilization strategy which stiffens the knee joint which not only is unsuccessful but may lead to excessive joint contact forces which have the potential to damage articular structures. The copers use a strategy which permits normal knee kinematics and bodes well for joint integrity.

Introduction

The principal function of the anterior cruciate ligament is to prevent anterior translation of the tibia relative to the femur. Anterior cruciate ligament rupture typically results in loss of knee joint stability, strength of the surrounding musculature, and function 6, 15. Patients often complain of the knee giving way after anterior cruciate ligament rupture, a symptom of instability. Patients usually require reconstructive surgery to reestablish functional stability of the knee 2, 5, 19. Several recent studies, however, have reported successful outcomes after non-operative management in patients who have ruptured the anterior cruciate ligament, but generally, only after they have adapted their lifestyles by mitigating activity levels 2, 5, 1, 4.

There are anterior cruciate ligament deficient individuals who can maintain high activity levels, experiencing neither instability, loss of function or weakness despite complete rupture of the anterior cruciate ligament 5, 18. The knee does not give way, even under stressful conditions like jumping and pivoting. These individuals are able to return to all pre-injury activities without reconstructive surgery [5]and often without the use of a brace [7]. We have categorized these people as copers, because they appear to have either an intrinsic, or rapidly developed mechanism of compensating for the ruptured ligament.

Historically, the effects of anterior cruciate ligament rupture on muscle strength and function have been compared to those of healthy subjects without regard for how well or how poorly the patients compensate for the ruptured ligament; inclusion in these studies involved the ligament rupture alone (e.g. ‘All subjects were anterior cruciate ligament deficient‘). Studies involving free speed walking have shown mixed results. Some authors report significant abnormalities 1, 28, whereas others do not 9, 12, 16, 27. Most authors agree that measurable disturbances in kinetics, kinematics and patterns of muscle activation exist during more stressful activities 4, 9, 12, 28; however, there is no consensus about what constitutes a typical response to stressful activities in the face of anterior cruciate ligament deficiency 2, 3, 8. Copers comprise a small percentage of the patient population with anterior cruciate ligament rupture but their ability to stabilize the ACL deficient knee during high level activities suggests that their movement patterns are different from those who cannot stabilize their knees. Failure to distinguish the copers from non-copers in studies of ACL deficient individuals may have resulted in the inconsistencies in movement patterns found in the literature.

It was expected that the non-copers in our sample would demonstrate gait abnormalities much like those previously reported in the literature. Since copers seem to function as if their ligaments were still intact we anticipated that their gait patterns would be more like those reported in healthy subjects [18]. We also predicted that to maintain normal gait patterns, copers would have stronger quadriceps femoris muscles than the non-copers. The purpose of this study was to describe the kinematic and kinetic differences between a group of subjects who compensated well for anterior cruciate ligament injury (copers) and a group who did not (non-copers).

Section snippets

Subjects

Sixteen subjects with complete rupture of the anterior cruciate ligament (documented via arthroscopy or magnetic resonance imaging), served as subjects for this study. Eight had reported instability with activities of daily living and were scheduled for reconstructive surgery; these subjects were categorized as non-copers. Eight subjects met our operational definition of coper by having returned to all pre-injury activity without limitation and by rating their current level of knee function as

Results

There was a trend toward less quadriceps muscle strength in the ACL deficient limbs of the non-coper group whose average quadriceps index was 88.3% (± 12.5%) compared to 98.9% (± 9.8%) in the coper group (t=1.844, p=0.088). The self rating scores, reported as a percentage of knee function prior to injury, were significantly different with the non-copers rating involved knee function at 53.6% (± 9.4%) whereas the copers rated involved knee function at 92% (± 8.4%) (t=8.259, p=0.000).

There was a

Discussion

Our hypothesis that the coper and non-coper samples would demonstrate different gait patterns that were unrelated to the amount of joint laxity was supported by the data. Neither group, however, walked ‘normally’. The classification of anterior cruciate ligament deficient subjects into copers and non-copers allowed us to clarify the gait abnormalities in this population. The copers in this study were selected based on their being ‘the best of the best’ and served as a template for how

Conclusions

Copers are a distinct subset of the anterior cruciate ligament deficient population who are able to fully compensate for the absence of the ligament. Despite ligamentous laxity that was greater and chronicity of injury that was longer than that of the non-copers, the copers in this study had quadriceps femoris muscle strengths, and knee joint motion in walking and jogging indistinguishable from their uninvolved knees. Non-copers compensate for the absence of the anterior cruciate ligament

Dr. Snyder-Mackler is an Associate Professor in the Department of Physical Therapy at the University of Delaware. She also holds a faculty appointment at Allegheny University and is the Director of Sports Medicine Research for the Orthopedic Sports Medicine Fellowship at Thomas Jefferson University in Philadelphia. She maintains an active Sports Physical Therapy practice at the University of Delaware and serves as a rehabiltation consultant to several professional teams. She is a Board

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    • Knee flexion angle and muscle activations control the stability of an anterior cruciate ligament deficient joint in gait

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      Citation Excerpt :

      Lower VL activity without any decrease in VM was also observed in the ACLD limbs when compared to their intact contralateral limbs during gait (Busch et al., 2019). Smaller flexion moments have been recorded in the early stance of noncopers (Alkjaer et al., 2003; Hurd and Snyder-Mackler, 2007; Kaplan, 2011; Rudolph et al., 1998) and copers (Rudolph et al., 1998) alike. At the second half of stance (i.e., 50 and 75%) under external extension moments (knee flexors activated), the stabilizing strategy involved smaller forces in gastrocnemii whereas larger forces in hamstrings with forces in quadriceps remaining nearly constant (Fig. 6).

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    Dr. Snyder-Mackler is an Associate Professor in the Department of Physical Therapy at the University of Delaware. She also holds a faculty appointment at Allegheny University and is the Director of Sports Medicine Research for the Orthopedic Sports Medicine Fellowship at Thomas Jefferson University in Philadelphia. She maintains an active Sports Physical Therapy practice at the University of Delaware and serves as a rehabiltation consultant to several professional teams. She is a Board Certified Sports Physical Therapist and concentrates her clinical practice and research in the areas of knee, back and shoulder rehabilitation, and electrical stimulation of muscle. She has authored a textbook on electrotherapy and many research publications in the areas of knee, shoulder and back rehabiltation and neuromuscular electrical stimulation. She served as Head Trainer for the beach volleyball venue at the '96 Olympic Games in Atlanta.

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    Michael Axe, a partner in First State Orthopedics, received his M.D. from Jefferson Medical College in Philadelphia. He completed his orthopedic residency at the University of Pittsburgh and a fellowship in sports orthopedic medicine at the Hughston Sports Medicine Hospital in Columbus, Georgia. He is a clinical associate professor and course director in the physical therapy department at the University of Delaware. He is a member of the American College of Sports Medicine and a fellow of the Anerican Academy of Orthopedic Surgeons. He is the regional physician for the United States Weightlifting Federation and has made numerous presentations and published many articles related to orthopedics and sports medicine.

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    Katherine Rudolph received a B.S. in Geology from Syracruse University, and an M.S. in Physical Therapy from Boston University in 1989. She joined the staff of the Physical Therapy Department of the Massachusetts General Hospital in 1989 and in 1991 became the Clinical Research Physical Therapist in the Orthopedic Biomechanics Laboratory of the Shriner's Hospital, San Francisco Unit. Ms. Rudolph is currently a doctoral candidate in the Interdisciplinary Program in Biomechanics and Movement Science at the University of Delaware and is a member of the American Association for Physical Therapy and the North American Society for Gait and Clinical Motion Analysis.

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    Martha Eastlack received a B.S. in Biology from Oglethorpe University, an M.S. in Physical Therapy from Boston University, and a Ph.D. in Physiology and Anatomy from the University of Delaware. She has had clinical experience at the National Rehabilitation Hospital in Washington, D.C. and in orthopedics and sports medicine in Newark and Wilmington, DE. The focus of her research is in the areas of muscle morphology and muscle performance. Dr. Eastlack is a member of the Sections for Research, Orthopedics and Education of the APTA and is a member of the American College of Sports Medicine.

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