• J. Steele
  • J. Brown
  • P. Milburn


INTRODUCTION Analysing adaptations to injury displayed by functional chronic anterior cruciate ligament deficient (ACLD) patients can provide useful information concerning successful compensatory techniques used following ACL rupturel. This information may form the basis of rehabilitation programs provided foracutely ACL injured athletes or to develop strategies for preventing ACL rupture episodes. Therefore, the purpose of this study was to examine the influence of chronic ACLD on forces and moments of force actingat the knee joint during an abmpt deceleration task. Methods Eleven functional chronic unilateral ACLD patients and 11 matched controls with no history of knee disease or trauma participated in the study. Ground reaction forces (GRF) were sampled (1000 Hz) as each subject landed in single-limb stance on a KISTLER force platform after receiving a chest level pass and then decelerating abruptly. Data were collected for 5 trials for both the subjects' right and left lower extremity. Sagittal plane kinematics of each subject's landing action were digitized from 16 rnrn high speed film (200 Hz). Joint reaction forces and sagittal planar net moments of force for the knee (Mk) were calculated using Newtonian equations of motion and inverse dynamics. Tibiofemoral joint shear (Fs) and compressive (Fc) forces were calculated from the net joint reaction forces and the patellar tendon force occasioned by the net moments and inertia forces predicted to be acting about the knee2. Biomechanical data reported by Niell2 were used to model knee joint musculoskeletal geometry in calculating Fs and Fc. The anteriorly directed Fs were less than body weight at initial contact (IC) but increased to mean peak values of 3.4 - 4.4 BW. There was no significant main effect of either subject group or test limb on any of the Fs calculated during the deceleration task. In contrast, the ACLD subjects displayed a significantly greater mean Limb-to-limb difference in Fc (0.14 ± 0.32 BW, p = 0.04) and Mk (28.52± 40.7 N*m, p = 0.009) at IC than the controls (Fc = -0.87±1.82; Mk = -18.9 ±36.8). However, no significant differences were found for any of the joint forces or knee moments generated at peak resultant GRF or on the peak values generated during deceleration. CONCLUSIONS Abrupt deceleration tasks create high anterior loading at the tibiofemoral joint, loads that exceed the ultimate tensile strength reported for human ACL specimens. It was concluded that ACLD subjects were able to perform this task without giving way of the knee by increasing tibiofemoral joint compressive forces and knee flexion moments at IC to stabilize the tibia in preparation to withstand the high shear forces. REFERENCES McNair PJ et al. (1989). In RJ Gregor et al. (Eds.), Proceedings of the XI1 International Congress of Biomechanics (abstract no. 184). LA, California: UCLA. Kuster M et al. (1994.). Knee Surg, Sports Traumatol, Arthroscopy 2:2-7.