The effect of open kinetic chain knee extensor resistance training at different training loads on anterior knee laxity in the uninjured.

BACKGROUND: The commonly used open kinetic chain knee extensor (OKCKE) exercise loads the sagittal restraints to knee anterior tibial translation. OBJECTIVE: To investigate the effect of different loads of OKCKE resistance training on anterior knee laxity (AKL) in the uninjured knee. STUDY DESIGN: non-clinical trial. METHODS: Randomization into one of three supervised training groups occurred with training 3 times per week for 12 weeks. Subjects in the LOW and HIGH groups performed OKCKE resistance training at loads of 2 sets of 20 repetition maximum (RM) and 20 sets of 2RM, respectively. Subjects in the isokinetic training group (ISOK) performed isokinetic OKCKE resistance training using 2 sets of 20 maximal efforts. AKL was measured using the KT2000 arthrometer with concurrent measurement of lateral hamstrings muscle activity at baseline, 6 weeks and 12 weeks. RESULTS: Twenty six subjects participated (LOW n = 9, HIGH n = 10, ISOK n = 7). The main finding from this study is that a 12-week OKCKE resistance training programme at loads of 20 sets of 2RM, leads to an increase in manual maximal AKL. CONCLUSIONS: OKCKE resistance training at high loads (20 sets of 2RM) increases AKL while low load OKCKE resistance training (2 sets of 20RM) and isokinetic OKCKE resistance training at 2 sets of 20RM does not.

Effect of repeated passive anterior loading on human knee anterior laxity.

BACKGROUND: Increased knee anterior laxity results when the anterior cruciate ligament is injured. This increased laxity can cause knee dysfunction. Until recently this laxity was believed to be only diminished through surgery. But recent findings indicate that knee anterior laxity may be decreased with repeated loading of the knee. OBJECTIVE: The purpose of this study was to test the hypothesis that regular passive anterior loading of the uninjured human knee would enhance its stiffness. STUDY DESIGN: Randomized controlled trial. METHODS: Knee anterior laxity was tested using an arthrometer in 22 young, uninjured females before, during and after a 3 month period during which passive anterior loading was applied by a trained physiotherapist over 5 sessions per week to a randomly assigned knee. RESULTS: Knee anterior laxity was not affected by the passive anterior loading of the knee. CONCLUSIONS: Given that in this study repeated passive loading of the knee did not change knee anterior laxity, it would be easy to conclude that this training is ineffective and no further research is required. We caution against this given the relatively short duration and possibly insufficient intensity of the training and the population studied; individuals with normal joint laxity. We recommend that future research be performed that consists of individuals with lax joints who receive training for prolonged periods.

The effect of knee extensor open kinetic chain resistance training in the ACL-injured knee.

PURPOSE: To investigate the effect of different loads of knee extensor open kinetic chain resistance training on anterior knee laxity and function in the ACL-injured (ACLI) knee. METHODS: Fifty-eight ACLI subjects were randomised to one of three (12-week duration) training groups. The STAND group trained according to a standardised rehabilitation protocol. Subjects in the LOW and HIGH group trained as did the STAND group but with the addition of seated knee extensor open kinetic chain resistance training at loads of 2 sets of 20 repetition maximum (RM) and 20 sets of 2RM, respectively. Anterior knee laxity and measurements of physical and subjective function were performed at baseline, 6 and 12 weeks. Thirty-six subjects were tested at both baseline and 12 weeks (STAND n = 13, LOW n = 11, HIGH n = 12). RESULTS: The LOW group demonstrated a reduction in 133 N anterior knee laxity between baseline and 12 weeks testing when compared to the HIGH and the STAND groups (p = 0.009). Specifically, the trained-untrained knee laxity decreased an average of approximately 5 mm in the LOW group while remaining the same in the other two groups. CONCLUSION: Twelve weeks of knee extensor open kinetic chain resistance training at loads of 2 sets of 20RM led to a reduction in anterior knee laxity in the ACLI knee. This reduction in laxity does not appear to offer any significant short-term functional advantages when compared to a standard rehabilitation protocol. These results indicate that knee laxity can be decreased with resistance training of the thigh muscles. LEVEL OF EVIDENCE: Randomised controlled trial, Level II.

The effect of thigh muscle activity on anterior knee laxity in the uninjured and anterior cruciate ligament-injured knee.

PURPOSE: The main purpose of this study was to describe the nature of the relationship between hamstring muscle activity and anterior knee laxity. METHODS: This was a cross-sectional study. Anterior knee laxity was measured at 133N and manual maximal forces using the KT2000 knee arthrometer, in 8 ACL-injured and 13 uninjured individuals. Electromyographic activity of the lateral hamstrings was measured during laxity testing. Subjects contracted the hamstrings during anterior knee laxity testing at eight predetermined levels of maximal voluntary isometric contraction. RESULTS: Volitional contraction of the lateral hamstrings reduced anterior knee laxity logarithmically for both the 133N and manual maximal tests in both the ACL-injured and uninjured knees. A simple linear regression model, with the log of percentage of maximum lateral hamstrings activity as the sole predictor, explained approximately 70-80% of the variation in anterior knee laxity. Both ACL-injured and uninjured subjects reduced anterior knee laxity at the same rate with increases in muscle activity. However, initial lateral hamstrings muscle activity had a greater effect on percentage anterior knee laxity scores in the ACL-injured as compared to the uninjured knee. CONCLUSIONS: Lateral hamstrings activity reduces anterior knee laxity in a nonlinear manner, whereby the initial lower level of activation produces the greatest change in anterior knee laxity. Therefore, hamstrings muscle activity must be monitored during anterior knee laxity testing.

Bench testing of a knee joint arthrometer.

The KT1000 and KT2000 knee joint arthrometers (MEDmetric Corp, San Diego, California) have been shown to overestimate the measurement of knee joint sagittal laxity. The purpose of this study was to investigate the accuracy of the KT arthrometers as measures of anterior and posterior linear displacement. The anterior and posterior linear displacements of 3 KT arthrometers (2 KT1000 arthrometers and 1 KT2000 arthrometer) were compared with the simultaneous displacement measured by a precision linear Vernier Dial Test Indicator (Davenport Ltd, London, United Kingdom). The displacement calculated using the analog output of the KT2000 was also compared with the values on the KT2000 displacement dial. Compared with the Vernier Dial Test Indicator, the KT arthrometers overestimated anterior linear displacement by between 22% and 24%. True anterior displacement for all 3 arthrometers, as recorded by the Vernier Dial Test Indicator, was found by multiplying the KT value by 0.79. When compared with the Vernier Dial Test Indicator, the KT arthrometers underestimated posterior linear displacement by between 18% and 19%. True posterior displacement, as recorded by the Vernier Dial Test Indicator, was found by multiplying the KT1000 value by 1.17 and the KT2000 value by 1.16. The internal apparatus of the KT2000 and KT1000 knee joint arthrometers overestimates anterior displacement and underestimates posterior displacement with a predictable relative systematic error. Future validation studies should use these correction equations to assess the accuracy of the KT arthrometers. Sagittal plane knee laxity measured with the KT devices requires systematic correction for optimal accuracy.

Robotic knee laxity testing: reliability and normative data.

PURPOSE: To evaluate the reliability of the GeNouRoB knee arthrometer and present normative values of knee anterior laxity using this device on young females. METHODS: Anterior laxity in both knees was tested in two groups of young, uninjured females using the hamstrings electromyography biofeedback feature of the device. There were 13 participants in the group tested for reliability and 23 for the normative study. Laxity (mm of movement of the proximal tibia in the anterior direction relative to the femur) was calculated at test forces of 134 N and 250 N with values presented for the unstandardised and standardised (relative to stabilisation force) conditions. RESULTS: The relative reliability (95% limits of agreement) of the device for laxity at a test force of 134 N was 2 to 3mm. Left knee anterior laxity was almost 1mm greater than the right. CONCLUSIONS: The relative reliability of the GeNouRoB arthrometer is comparable to the KT device. In agreement with previous work on the nonrobotic KT arthrometer, the knee anterior laxity values found with the GeNouRoB are greater in the left as compared to the right knee.

The immediate effects of open kinetic chain knee extensor exercise at different loads on knee anterior laxity in the uninjured.

BACKGROUND: There is evidence that anterior laxity may be affected by knee extensor open kinetic chain (OKC) exercise with responses being load-dependent. The aim of this study is to evaluate the immediate and short-term changes in passive knee anterior laxity following a single session of OKC knee extensor exercise. METHODS: Thirty two participants were randomly allocated to perform either high load (20 sets of 2 repetitions) or low load (2 sets of 20 repetitions) knee extensor OKC exercise with knee anterior laxity assessed before exercise, immediately after exercise and 45 and 90min after exercise with a KT-2000 arthrometer using a 133N force. RESULTS: A significant effect of time was observed on knee laxity (p<0.001). However, a significant interaction of time and group was not found (p=0.54) and so the results presented here are for the combined (low and high load) group mean±standard deviation knee anterior laxity (mm) in the exercised leg: 7.2±2.2 (baseline), 8.2±2.3 (immediate post exercise, 14% change from baseline), 8.1±2.3 (45min post exercise, 12% change from baseline), and 7.7±2.2/0.29 (6.9) (90min post exercise, 7% change from baseline). CONCLUSION: OKC knee extensor exercise at high loads and low loads causes an immediate increase in knee laxity that begins to decrease within 90min.