David M. Hooper

Open and Closed Kinetic Chain Exercises in the Early Period after Anterior Cruciate Ligament Reconstruction: Improvements in Level Walking, Stair Ascent, and Stair Descent

Thirty-seven patients who had undergone anterior cruciate ligament reconstruction were tested in a gait analysis laboratory at 2 and 6 weeks after surgery. Between test sessions, patients were randomly assigned to a course of either closed or open kinetic chain resistance exercises (3 sessions per week for 4 weeks). Gait analysis consisted of bilateral calculations of knee joint angle, moment, and power during level walking, stair ascent, and stair descent. An analysis of variance on the effects of training group and test session indicated that the only variable to be significantly affected by the type of exercise program was the amount of knee flexion at the beginning of step-up (P<0.05). All other measures of knee angle, moment, and power (16 total variables) showed no significant difference between the exercise groups. All variables measured on the injured side showed significant improvement from test 1 to test 2 (P<0.05), but the injured leg remained functionally deficient when compared with the uninjured leg. These data suggest that there are no clinically significant differences in the functional improvement resulting from the choice of open or closed kinetic chain exercises in the early period after this surgery.

Gait analysis 6 and 12 months after anterior cruciate ligament reconstruction surgery.

Little is known about knee function after anterior cruciate ligament reconstruction in the vital activities of walking and stair use. Gait analysis was done on patients 6 months (n = 8) and 12 months (n = 9) after reconstruction of the anterior cruciate ligament. Paired t tests were used to compare the injured and uninjured knees. During level walking, the patients placed external flexion torques on their injured knees throughout midstance, indicating the absence of quadriceps avoidance gait. The peak external flexion torque (resisted by the knee extensor muscles) placed on the injured knee was significantly less than that of the uninjured knee when ascending stairs (at 12 months, 68.4 and 85.3 N-m in the injured and uninjured knees, respectively) and also when descending stairs (at 12 months, 70.8 and 81.7 N-m in the injured and uninjured knees, respectively). The injured knee produced significantly less power than the uninjured knee when ascending stairs, but this difference was not significant when descending stairs. These findings indicate that asymmetric gait patterns persisted up to 1 year after surgical reconstruction and were more pronounced during stair ascent and descent than in level walking. These results indicate that clinicians should include specific interventions targeted at improving knee function during stair use to restore normal function after anterior cruciate ligament reconstruction.

Reliability of leg muscle electromyography in vertical jumping

Abstract In this study we aimed to determine the reliability of the surface electromyography (EMG) of leg muscles during vertical jumping between two test sessions, held 2 weeks apart. Fifteen females performed three maximal vertical jumps with countermovement. The displacement of the body centre of mass (BCM), duration of propulsion phase (time), range of motion (ROM) and angular velocity of the knee and surface EMG of four leg muscles (rectus femoris, vastus medialis, biceps femoris and gastrocnemius) were recorded during the jumps. All variables were analysed throughout the propulsion and mid-propulsion phases. Intraclass correlation coefficients (ICC) for the rectus femoris, vastus medialis, biceps femoris and gastrocnemius were calculated to be 0.88, 0.70, 0.24 and 0.01, respectively. BCM, ROM and time values all indicated ICC values greater than 0.90, and the mean knee angular velocity was slightly lower, at 0.75. ICCs between displacement of the BCM and integrated EMG (IEMG) of the muscles studied were less than 0.50. The angular velocity of the knee did not correlate well with muscle activity. Factors that may have affected reliability were variations in the position of electrode replacement, skin resistance, cross-talk between muscles and jump mechanics. The results of this study suggest that while kinematic variables are reproducible over successive vertical jumps, the degree of repeatability of an IEMG signal is dependent upon the muscle studied.

Relationship of leg muscle strength and knee function in the early period after anterior cruciate ligament reconstruction.

The purpose of this descriptive study was to assess the relationship between knee function and the strength testing performance of various leg muscles in the early period after anterior cruciate ligament reconstruction (ACLR). Twenty‐four patients who had recent ACLR (seven females and 17 males, mean age=27 years) were tested for leg muscle strength and knee function 2 weeks after surgery. The concentric peak torques of the hip and knee extensors and knee flexors were measured at 210° s−1. In addition, the latter two muscle groups were measured at 60° s−1, and also isometrically (at a knee angle of 60°). Knee function was assessed using a three‐dimensional motion analysis system combined with a force platform. This system determined knee joint angles, torques and powers during level walking, stair ascent and stair descent. Pearsons correlation coefficients were calculated to assess the relationships between the injured knee function variables and the injured/uninjured strength ratios. The correlation coefficients ranged (in absolute value) from 0.03 to 0.81, and were generally higher for the stair tasks compared with level walking, and highest for the knee extensors (as compared with the knee flexors and hip extensors), and the strength test velocity appears much less important than the muscle group tested. These results contribute evidence indicating the importance of knee extensor strength to knee function in the early period after ACLR.

A Dynamic Approach to Spinal Instability: Part Ii: Hesitation and Giving-way During Interspinal Motion

Study Design. Human lumbar functional spinal units (FSUs) were moved throughout their range of motion in sagittal and lateral bending, while the dynamics of this movement were computed in vitro. Functional spinal units were tested intact and after subsequent discectomy and unilateral facetectomy. Objective. To determine whether the patterns of small jerks observed during intersegmental motion are sensitive to spinal instability. Summary of Background Data. Small jerks have been observed as hesitation during increasing velocity and as giving way during decreasing velocity in the experiments described in Part I of this study. Methods. Human lumbar functional spinal units were moved from extension to flexion, flexion to extension, left to right, and right to left, by a pure moment. Range of motion and velocity and acceleration patterns of the main and coupled motions were evaluated in six degrees of freedom by position changes of attached infrared light‐emitting diodes recorded by cameras. Functional spinal units were tested in three surgical conditions (intact, discectomy, and unilateral facetectomy) under two preload conditions (no preload and 400‐N preload). Discontinuous accelerations and decelerations (jerks) were computed in these motions and their location in relation to the main angular motion determined. Results. Jerks were observed in almost all motions, in the intact functional spinal units and after surgery. The parameters describing the magnitude of the jerk decreased with increasing component instability. In the sagittal plane, there was a surgical condition by motion direction interaction (P < 0.014) regarding the location of the jerk. Independent from the motion direction, the jerk occurred around the neutral position (in relation to the primary angular motion) in the intact functional spinal units, whereas it shifted from the neutral position toward the beginning of the motion with increasing component instability. Conclusion. The results suggest that a small jerk is a normal component of fast intersegmental motion. The jerk has a certain magnitude and location in an intact functional spinal unit, whereas both of the parameters describing the jerk are sensitive to component instability.

Gait adaptations in patients with chronic posterior instability of the knee

OBJECTIVE A retrospective analysis was performed to assess gait in individuals with a long history of posterior knee instability. DESIGN Descriptive study. BACKGROUND There are few studies in the literature concerning evaluation of the biomechanics of the knee in patients with knee posterior instability. METHODS Nine individuals with posterior knee instability and a matched control group of uninjured subjects were tested in regards to knee kinematics and kinetics while walking and ascending and descending stairs. The mean follow up time for the individuals with posterior instability was 11.1 years. Individual satisfaction with the knee was measured by having participants complete the Flandry (also known as Hughston Clinic) self-assessment questionnaire. RESULTS It was found that patients with knee posterior instability who indicated a higher level of satisfaction on the Flandry score walked in a manner that demonstrated greater peak knee extensor torque during stance phase, while less satisfied patients with knee posterior instability demonstrated lower peak knee extensor torque. There was a significant correlation between the self-assessment score and the peak knee extensor torque during level walking (P=0.003). During stair ascent and descent, patients with posterior instability averaged lower knee extensor torque and power than the control subjects, but those differences were only statistically significant in power while descending stairs (P=0.048). CONCLUSIONS Individuals with chronic knee posterior instability modify their gait, and the adaptation can be predicted based upon the individuals self-assessment of their knee using the Flandry questionnaire. RELEVANCE These data suggest that gait retraining may be a valuable addition to the traditional muscle strengthening programs, which are commonly used during conservative management of knee posterior instability.

Validation of the Hughston Clinic subjective knee questionnaire using gait analysis.

INTRODUCTION Subjective questionnaires, completed by the patient, are often used to document the status of a disabled knee. The purpose of this study was to validate the Hughston Clinic subjective knee questionnaire by describing how knee kinematics and kinetics correlated to subjective knee scores after knee injury and surgery. METHODS Five groups were studied: patients 2 (N = 37), 6 (N = 37), and 24 (N = 8) wk after ACL reconstruction (ACLR); patients with a chronic PCL deficiency (N = 9); and uninjured controls (N = 8). A three-dimensional motion analysis system and force platform were used to measure flexion angles and knee moments during level walking and stair climbing. RESULTS Hughston Clinic questionnaire scores were significantly correlated to mechanical descriptors measured during stair ascent and descent in the 2- and 6-wk ACLR groups (P < 0.05). The Hughston Clinic questionnaire score was correlated to several kinematic variables in the ACL reconstructed knee at 24 wk postoperative, e.g., knee flexion during walking. In the PCL deficient group, the Hughston Clinic questionnaire score was correlated with several kinetic measures, e.g., the peak moment (knee extensors). The Hughston Clinic questionnaire score was not correlated to knee mechanics in the control group. CONCLUSION The Hughston Clinic questionnaire score has been shown to be valid in this study as it reflects some mechanical descriptors during activities of daily living in the first 6 wk post ACL reconstruction. The questionnaire also provides information on gait modifications by people coping with knee injuries.

Range of Motion Specificity Resulting From Closed and Open Kinetic Chain Resistance Training After Anterior Cruciate Ligament Reconstruction

The purpose of this study was to examine whether joint angle specificity occurs in open and closed kinetic chain resistance training of the knee extensors after anterior cruciate ligament reconstruction (ACLR). Isokinetic knee extensor strength was measured at 60 and 210°·s-1 in 32 patients, 2 and 6 weeks after surgery. Between test sessions, patients participated in a 4-week program of injured leg resistance training of the knee extensors in either open kinetic chain (OKC) knee extension or leg press exercises. Isokinetic testing knee range of motion (ROM) was divided into 5 equal portions from flexion to extension, and the mean torque was calculated over those divisions: 0–20%, 20–40%, 40–60%, 60–80%, and 80–100% ROM. Analysis of variance indicated that there were no significant differences between patients in the knee extension or leg press exercise groups.

Three dimensional moments in the lumbar spine during asymmetric lifting

OBJECTIVE: To better understand the loads placed on the spine during asymmetric lifting. DESIGN: Analysis of variance was used to test the effects of asymmetry (0, 45, 90 degrees ), event (up, down, min and max), and trial (first and second) on applied spine moments and resulting EMG signals in the lumbar spine. BACKGROUND: Loading conditions resulting from symmetric lifting are well documented in the literature, yet free-style asymmetric tasks have not been intensively studied. METHODS: Infrared markers and EMG electrodes were fixed to ten subjects. Subjects were asked to lift a 45 N weight from three different positions in relation to the sagittal plane. External loads on the L3-L4 and L4-L5 disc planes were calculated. Maximum moments and EMG were compared with those at lift off and set down of the burden. All lifts were repeated twice. RESULTS: Introducing asymmetry to the lift increased lateral bending and twisting moments. Flexion moments increased by approximately 5% after lift off of the load. During the second repetition of the lift, flexion and twisting moments decreased and increased, respectively. EMG signals were greater on the contralateral side during asymmetric lifts. CONCLUSIONS: Asymmetric lifting places complex loads across the trunk, which may become increasingly asymmetric with repeated trials. RELEVANCE: Individuals should take precautions to perform lifts in a symmetric manner and to avoid repetitive asymmetric lifting if possible. Past study indicated that twisting and lateral bending loads, when coupled with flexion loads, resulted in much greater disc compression and should be avoided. This work described the degree to which lateral bending and twisting loads were introduced as lifts deviated from the sagittal plane.

Velocity specificity in early training of the knee extensors after anterior cruciate ligament reconstruction.

Abstract Resistance-training velocity specificity is known to occur in isotonic training of uninjured subjects and in isokinetic training of injured patients. Whether velocity specificity occurs with isotonic training in injured patients has not been tested, despite the common use of this exercise mode in patients. Thirty-two patients recovering from anterior cruciate ligament reconstruction (ACLR) surgery were tested at approximately 2 and 6 weeks after surgery. The isokinetic injured/uninjured strength ratios of the knee extensors were compared for the test velocities of 60° · s−1 and 210° · s−1, as assessed before and after a 4-week training period. Isotonic training of the knee extensors at 60° · s−1 was applied in formal sessions three times per week. The isokinetic injured/uninjured strength ratios were compared for the two test velocities, and there was no indication that training velocity specificity occurred in these patients. Possible reasons for this finding, which contrasts with previous work, are discussed.