Gait mechanics in chronic ACL deficiency and subsequent repair Reed Ferber a, * , Louis R. Osternig b , Marjorie H. Woollacott b , Noah J. Wasielewski b , Ji-Hang Lee b a Department of Physical Therapy, University of Delaware, 301 McKinly Lab, Newark, DE 19716-2591, USA b Department of Exercise and Movement Science, University of Oregon, Eugene, OR 97403, USA Received 23 October 2001; accepted 1 March 2002 Abstract Objective. To determine how normal gait patterns may change as a result of chronic anterior cruciate ligament deficiency and subsequent reconstructive surgery. Design. Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and 3 months following reconstructive surgery, and 10 uninjured controls. Background. There is controversy whether persons with chronic anterior cruciate ligament deficiency develop a ‘‘quadriceps avoidance’’ pattern and how anterior cruciate ligament reconstructive surgery influences gait mechanics in these same individuals. Methods. Gait analysis was employed to determine kinematic, kinetic, and muscle Electromyographic data. Results. Prior to surgery, no anterior cruciate ligament deficient subject exhibited a quadriceps avoidance pattern. Following surgery, the subjects exhibited a significantly greater knee extensor moment during early stance as compared to the control group. Prior to and following surgery, anterior cruciate ligament deficient subjects demonstrated a significantly greater hip extensor mo- ment possibly to reduce anterior tibial translation. Conclusions.Thesedatasuggestthat(1)developmentofaquadricepsavoidancepatternislesscommonthanpreviouslyreported, (2) anterior cruciate ligament deficient subjects accommodate through alterations of hip joint mechanics, (3) surgical repair sig- nificantly alters lower extremity gait patterns, and (4) re-establishment of pre-injury gait patterns takes longer than 3 months to occur. Relevance The results suggest that chronic anterior cruciate ligament deficient subjects do not exhibit a quadriceps avoidance gait pattern. Surgicalinterventionsignificantlyalterslowerextremitygaitmechanicsinapopulationthathasaccommodatedtoanteriorcruciate ligament deficiency. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Anterior cruciate ligament; Quadriceps avoidance; Gait; Surgery 1. Introduction It has been hypothesized that injury and subsequent repair of the anterior cruciate ligament (ACL) leads to alterations in lower extremity joint kinetics, kinematics, and energetic patterns during gait. These gait patterns may develop as a result of muscle adaptations and neuromuscular reprogramming, possibly in response to pain or instability, to stabilize the knee and to prevent re-injury during gait [1–3]. It has also been demon- strated that acute (<1 month post-injury) ACL injured patients exhibit significantly different knee moment pat- terns during gait compared to chronic (>2 years post injury)ACLdeficientsubjects[1,2].Individualswhohad recently suffered ACL injury exhibited a sustained knee extensor moment throughout stance compared to non- injuredcontrolsubjects[2].Thisgaitpatternmayresult from factors such as knee joint swelling, joint tissue derangement, or muscle inhibition due to pain. It has been suggested that, over time, ACL deficient individ- uals develop a sustained knee flexor moment during mid-stance (MS). This has been termed a ‘‘quadriceps avoidance’’ pattern, possibly serving to reduce ante- rior tibial shear during gait [1,3–6]. However, other in- vestigations have found no evidence of a quadriceps * Corresponding author. E-mail address: reedferb@udel.edu (R. Ferber). 0268-0033/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0268-0033(02)00016-5 Clinical Biomechanics 17 (2002) 274–285 www.elsevier.com/locate/clinbiomech