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BACKGROUND: Menstrual cycle phase has been correlated with risk of noncontact anterior cruciate ligament injury in women. The mechanism by which hormonal cycling may affect injury rate is unknown. HYPOTHESES: Jumping and landing activities performed during different phases of the menstrual cycle lead to differences in foot strike knee flexion, as well as peak knee and hip loads, in women not taking an oral contraceptive but not in women taking an oral contraceptive. Women will experience greater normalized joint loads than men during these activities. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-five women (13 using oral contraceptives) and 12 men performed repeated trials of a horizontal jump, vertical jump, and drop from a 30-cm box on the left leg. Lower limb kinematics (foot strike knee flexion) and peak externally applied moments were calculated (hip adduction moment, hip internal rotation moment, knee flexion moment, knee abduction moment). Men were tested once. Women were tested twice for each phase of the menstrual cycle (follicular, luteal, ovulatory), as determined from serum analysis. An analysis of variance was used to examine differences between phases of the menstrual cycle and between groups (alpha = .05). RESULTS: No significant differences in moments or knee angle were observed between phases in either female group or between the 2 female groups or between either female group and the male controls. CONCLUSIONS: Variations of the menstrual cycle and the use of an oral contraceptive do not affect knee or hip joint loading during jumping and landing tasks. CLINICAL RELEVANCE: Because knee and hip joint loading is unaffected by cyclic variations in hormone levels, the observed difference in injury rates is more likely attributable to persistent differences in strength, neuromuscular coordination, or ligament properties. [ABSTRACT FROM AUTHOR]

OBJECTIVE: This study tested the hypothesis that gait changes related to knee osteoarthritis (OA) of varied severity are associated with increased loads at the ankle, knee, and hip. METHODS: Forty-two patients with bilateral medial compartment knee OA and 42 control subjects matched for sex, age, height, and mass were studied. Nineteen patients had Kellgren/Lawrence (K/L) radiographic severity grades of 1 or 2, and 23 patients had K/L grades of 3 or 4. Three-dimensional kinematics and kinetics were measured in the hip, knee, and ankle while the subjects walked at a self-selected speed. RESULTS: Patients with more severe knee OA had greater first peak knee adduction moments than their matched control subjects (P = 0.039) and than patients with less severe knee OA (P < 0.001). All patients with knee OA made initial contact with the ground with the knee in a more extended position than that exhibited by control subjects. An increased axial loading rate was present in all joints of the lower extremity. Patients with more severe knee OA had lower hip adduction moments compared with their matched control subjects. CONCLUSION: The secondary gait changes observed among patients with knee OA reflect a potential strategy to shift the body's weight more rapidly from the contralateral limb to the support limb, which appears to be successful in reducing the load at the knee in only patients with less severe knee OA. The increased loading rate in the lower extremity joints may lead to a faster progression of existing OA and to the onset of OA at joints adjacent to the knee. Interventions for knee OA should therefore be assessed for their effects on the mechanics of all joints of the lower extremity. [ABSTRACT FROM AUTHOR]

BACKGROUND: Increased valgus loading at the knee has been previously identified as a possible risk factor for noncontact anterior cruciate ligament injuries, which are common in sports. Arm position variation may affect risk of injury by altering valgus knee loading. HYPOTHESIS: Sport-dependent variations in arm position increase valgus loading of the knee during run-to-cut maneuvers. STUDY DESIGN: Controlled laboratory study. METHODS: Eleven subjects performed a sidestep cutting maneuver, first with no arm constraints and then with 3 sports-related arm positions in random order (holding a lacrosse stick, holding a football on the plant side, and holding a football on the cut side). The analysis focused on the knee valgus moment relative to the arm positions during the landing phase of the activity. RESULTS: Arm position significantly influenced the valgus moment with an increase in the lacrosse trials and in the plant-side football trials but not in the cut-side football trials (alpha = .05). CONCLUSIONS: Constraining the plant-side arm results in increased valgus loading at the knee during run-to-cut maneuvers, which suggests the possibility of greater risk of anterior cruciate ligament injury during these conditions. CLINICAL RELEVANCE: These results suggest that training methods that consider arm position as a risk factor could help reduce the risk of anterior cruciate ligament noncontact injury. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To determine whether reducing walking speed is a strategy used by patients with knee osteoarthritis (OA) of varying disease severity to reduce the maximum knee adduction moment. METHODS: Self-selected walking speeds and maximum knee adduction moments of 44 patients with medial tibiofemoral OA of varying disease severity, as assessed by using the Kellgren/Lawrence grade, were compared with those of 44 asymptomatic control subjects matched for sex, age, height, and weight. RESULTS: Differences in self-selected normal walking speed explained only 8.9% of the variation in maximum knee adduction moment for the group of patients with knee OA. The severity of the disease influenced the adduction moment-walking speed relationship; the individual slopes of this relationship were significantly greater in patients with less severe OA than in asymptomatic matched control subjects. Self-selected walking speed did not differ between patients with knee OA, regardless of the severity, and asymptomatic control subjects. However, knees with more-severe OA had significantly greater adduction moments (mean +/- SD 3.80 +/- 0.89% body weight x height) and were in more varus alignment (6.0 +/- 4.5 degrees ) than knees with less-severe OA (2.94 +/- 0.70% body weight x height; and 0.0 +/- 2.9 degrees, respectively). CONCLUSION: Patients with less-severe OA adapt a walking style that differs from that of patients with more-severe OA and controls. This walking style is associated with the potential to reduce the adduction moment when walking at slower speeds and could be linked to decreased disease severity. [ABSTRACT FROM AUTHOR]

This article discusses methods for evaluating the progression of osteoarthritis through dynamic functional imaging as opposed to current static techniques. Comparison is made between static and dynamic methods of evaluating knee alignment. The correlation between dynamic knee moments during gait and bone mineral content is discussed. Knee loading is considered in terms of high tibial osteotomy, knee braces, pain, and non-steroidal anti-inflammatory drugs. New image-processing techniques for quantitating cartilage loss are described, and computational methods for generating true three-dimensional (3-D) maps of cartilage thickness are developed. Finally, new approaches to cross-correlate magnetic resonance images with kinematic measurements are described. These new techniques promise to become powerful diagnostic tools to detect and characterize pathological load distributions across articular cartilage. [ABSTRACT FROM AUTHOR]

Five patients with symptomatic knee hyperextension thrusting patterns due to posterolateral ligament complex injury underwent gait analysis before and after a gait retraining program. Patients were trained to avoid knee hyperextension by 1) walking with their knees slightly flexed throughout stance, 2) maintaining ankle dorsiflexion in early stance, and 3) maintaining an erect trunk-hip attitude during stance. Kinematic and kinetic measurements were obtained using automated gait analysis. Four of the five patients significantly reduced hyperextension at the knee and abnormal motion patterns at the hip and ankle. Patients showed increases in knee flexion throughout stance conversions of knee flexion-extension moments to more normal biphasic patterns with a 79% decrease in extension moments at terminal extension, and a 22% decrease in knee adduction moments. Posttraining values also showed a 30% decrease in the calculated medial tibiofemoral loads (P < 0.05). At the hip, there were significant decreases in abduction and adduction moments (36% and 18%, respectively, P< 0.01). Ankle plantar flexion motion decreased significantly by 42% (P < 0.01). Gait retraining can alter the biomechanics of hip, knee, and ankle function to approximately normal levels, and therefore is recommended before ligament reconstruction because abnormal knee motions, if resumed postoperatively, can stretch soft tissue reconstructions. [ABSTRACT FROM AUTHOR]

Thirty-two patients with an ACL-deficient knee and lower limb varus alignment and 16 healthy controls were analyzed during level walking using a force-plate and optoelectronic system. The forces and moments of the lower limb and knee joint were measured and knee joint loads and ligament tensile forces were calculated using a mathematical model. The majority of patients (20 of 32) had an abnormally high adduction moment at the affected knee. The adduction moment showed a statistically significant correlation to high medial tibiofemoral compartment loads and high lateral soft tissue forces, but not to the degree of varus alignment on standing roentgenograms. Fifteen of 32 knees had abnormally high lateral soft tissue forces. We interpreted these gait findings as indicative of a medial shift in the center of maximal joint pressure and an increase in lateral soft tissue forces to achieve coronal plane stability. Further, there is the likelihood of separation of the lateral tibiofemoral joint and 'condylar lift-off' during periods of the stance phase. If this occurs, all of the load-bearing forces would shift to the medial tibiofemoral joint and relatively large tensile forces would occur in the lateral soft tissue restraints. The flexion moment, as related to the quadriceps muscle force, was significantly lower than the control knees in 40% of the involved knees, and the extension moment, as related to the hamstring muscle force, was significantly higher in 50% of the involved knees. We interpret this finding as a gait adaptation tending to diminish quadriceps muscle activity and enhance hamstring muscle activity to provide dynamic anteroposterior stability of the knee joint. The fundamental assumption of this paper is that any combination of conditions leading to higher medial joint forces is associated with factors leading to more rapid degeneration of the medial compartment in patients with ACL deficiency, varus deformity, and lax lateral ligaments. [ABSTRACT FROM AUTHOR]

The percent force changes in the posterior cruciate ligament were calculated using a previously validated computerized knee model after the femoral insertion sites were varied 2.5 and 5.0 mm in an anterior, posterior distal, anterior distal, and posterior distal direction. The tibial insertion sites were also varied 2.5 amd 5.0 mm in the medial, lateral, proximal, and distal directions. Percent force changes were measured over a range of 0 degrees to 90 degrees. These insertion sites simulated potential surgical placement errors. Results of this study demonstrated that the greatest percent force changes in the posterior cruciate ligament were at full extension. The greatest absolute percent force change between 0 degrees and 90 degrees of flexion was with a femoral insertion of the posterior cruciate ligament placed 5 mm anterior to its normal attachment site, which resulted in a 39% change in the posterior cruciate ligament force. Distal femoral site attachment had the least effect (10% at 5.0 mm). Alterations at the tibial attachment site were less sensitive than on the femur; the greatest absolute percent force changes occurred with medial and lateral attachment sites (14% and 15%, respectively, at 5.0 mm). A minimal amount of percent force changes were seen between 45 degrees and 75 degrees of knee flexion in all positions tested for both tibial and femoral attachment sites. This model suggests that, like the anterior cruciate ligament, the force in the posterior cruciate ligament is also sensitive to attachment site position. As in anterior cruciate ligament studies, the femoral attachment site was found to be more sensitive. The greatest percent force changes for the posterior cruciate ligament were seen at the extremes of the knee motion tested (i.e., 0 degreees and 90 degrees). The posterior cruciate ligament sensitivity to graft placement lends credence to the importance of anatomic reconstruction. Results of this study can also be extrapolated to help in designing early continuous passive motion and rehabilitation programs, with the safest range of knee motion between 45 degrees and 75 degrees. [ABSTRACT FROM AUTHOR]