Does knee osteoarthritis differentially modulate proprioceptive acuity in the frontal and sagittal planes of the knee?

OBJECTIVE: Impaired proprioception may alter joint loading and contribute to the progression of knee osteoarthritis (OA). Although frontal plane loading at the knee contributes to OA, proprioception and its modulation with OA in this direction have not been examined. The aim of this study was to assess knee proprioceptive acuity in the frontal and sagittal planes in patients with knee OA and healthy subjects. We hypothesized that proprioceptive acuity in both planes of movement will be decreased in patients with OA. METHODS: The study group comprised 13 patients with knee OA and 14 healthy age-matched subjects. Proprioceptive acuity was assessed in varus, valgus, flexion, and extension using threshold to detection of passive movement (TDPM) tests. Repeated-measures analysis of variance was used to assess differences in TDPM values between the 2 groups and across movement directions. Linear regression analyses were performed to assess the correlation of the TDPM between and within planes of movement. RESULTS: The TDPM was significantly higher (P<0.05) in the group with knee OA compared with the control group for all directions tested, indicating reduced proprioceptive acuity. Differences in the TDPM between groups were consistent across all movement directions, with mean differences as follows: for valgus, 0.94° (95% confidence interval [95% CI] 0.20-1.65°); for varus, 0.92° (95% CI 0.18-1.68°); for extension, 0.93° (95% CI 0.19-1.66°); for flexion, 1.11° (95% CI 0.38-1.85°). The TDPM measures across planes of movement were only weakly correlated, especially in the group with knee OA. CONCLUSION: Consistent differences in the TDPM between the group of patients with knee OA and the control group across all movement directions suggest a global, not direction-specific, reduction in sensation in patients with knee OA.

Proprioceptive acuity in the frontal and sagittal planes of the knee: a preliminary study.

Though the knee experiences three-dimensional loading during everyday tasks, assessment of proprioceptive acuity has typically been limited to the primary direction of movement, knee flexion and extension. While loading in the constrained directions (varus/valgus and internal/external rotation) may contribute to injury and joint disease, little information is available regarding proprioceptive acuity in these planes of movement. The primary aim of this study was to characterize proprioceptive acuity in the frontal plane (varus/valgus) and to compare it with sagittal plane (flexion/extension) proprioceptive acuity in healthy subjects. Proprioception was assessed in 17 young, healthy subjects (11 females, 6 males, ages 21-33 years) using the threshold to detection of passive movement (TDPM). TDPM was found to be significantly (P < 0.001) lower in the frontal plane [valgus: mean (SD) 0.60 (0.20)° and varus: 0.58 (0.23)°] compared with the sagittal plane [extension: 0.78 (0.34)°, flexion: 0.82 (0.48)°]; however, no significant differences were noted within the same plane of movement. Results from this preliminary study may suggest more accurate proprioceptive acuity in the frontal plane compared with the sagittal plane. While further examination is necessary to confirm this relationship, more accurate frontal plane acuity may reflect a protective neural mechanism which enables more precise neuromuscular control of the joint in this constrained plane of movement.

Evidence of gender-specific motor templates to resist valgus loading at the knee.

Gender differences in neuromuscular control of the lower extremity may contribute to increased injury risk in females, but the neurophysiological mechanisms underlying these differences remain unclear. In this study, we sought to explore the effect of gender on volitional and reflex neuromuscular responses to a rapid valgus perturbation at the knee applied under "intervene" and "do not intervene" conditions. Multiple 7 degrees ramp-and-hold valgus perturbations were applied at the neutrally extended knee of 12 male and 12 female healthy subjects, while surface electromyography over the quadriceps and hamstrings recorded the neuromuscular response. Volitional responses did not vary between groups, perhaps reflecting the relative novelty of the loading direction. However, reflex responses observed under the "do not intervene" paradigm did vary by gender. Males demonstrated much more frequent and consistent reflex muscle activation than females. Moreover, muscle activation patterns were gender-specific. Diminished responses in female subjects may indicate that the position-based valgus perturbation did not produce the necessary mechanical stimulus to elicit reflexes. These gender differences in reflex control of the knee provide new insight into the control of frontal-plane knee joint movement and loading and may elucidate the neuromechanical underpinnings associated with neuromuscular control.

The differential effects of gender, anthropometry, and prior hormonal state on frontal plane knee joint stiffness.

BACKGROUND: Gender differences in passive frontal plane knee stiffness may contribute to the increased anterior cruciate ligament injury rate in females. Gender-based stiffness differences have been attributed to anthropometric variations, but little data exist describing this relationship. Furthermore, sex hormone levels appear to influence joint stiffness, but the differential effects of instantaneous and prior hormonal concentrations remain unknown. This study sought to explore the effect of gender, prior hormonal status, and anthropometry on passive frontal plane knee joint stiffness. METHODS: Twelve males and 31 females participated. Females were grouped by hormonal contraceptive use (non users [n=11], monophasic contraceptive users [n=11], and triphasic contraceptive users [n=9]) and tested at the same point in the menstrual cycle. Subjects' right knee was passively stretched +/-7 degrees in the frontal plane at 3 degrees /s. Stiffness was estimated at three loading levels and normalized by body size to minimize anthropometric biases. A 4 (group)x3 (load) repeated measures analysis of variance was performed for both raw and normalized stiffness. Linear regression analyses were preformed between stiffness estimates and knee diameter and quadriceps femoris angle. FINDINGS: Males displayed significantly greater (P<0.05) frontal plane stiffness than females. When normalized, males displayed significantly greater stiffness in valgus (P<0.05), but not varus (P>0.05) than females. No significant effect (P>0.05) of prior hormonal state was found; however, when normalized, varus stiffness was significantly less for triphasic contraceptive users than the other female groups (P<0.05). Quadriceps femoris angle was negatively correlated and knee diameter was positively correlated to knee stiffness. INTERPRETATION: Consistent with earlier in vitro findings, our data may indicate that ligament material properties are gender specific. A deficit in passive knee joint stiffness may place a larger burden on the neuromuscular system to resist frontal plane loading in females.

Associations between frontal plane joint stiffness and proprioceptive acuity in knee osteoarthritis.

OBJECTIVE: It has been proposed that proprioceptive impairments observed in knee osteoarthritis (OA) may be associated with disease-related changes in joint mechanics. The aim of this study was to quantify joint proprioception and stiffness in the frontal plane of the knee in persons with and without knee OA and to report the associations between these 2 metrics. METHODS: Participants were 13 patients with knee OA and 14 healthy age-matched subjects. Proprioceptive acuity was assessed in varus and valgus using the threshold to detection of passive movement (TDPM) test. Passive joint stiffness was estimated as the slope of the normalized torque-angle relationship at 0° joint rotation (neutral) and several rotations in varus and valgus. Analyses of variance were performed to determine the effect of OA and sex on each metric. Linear regression was used to assess the correlation between the TDPM and joint stiffness. RESULTS: The TDPM was significantly higher (P < 0.05) in the OA group compared to the control group for both varus and valgus, but significant sex differences were observed. Passive joint stiffness was significantly reduced (P < 0.05) in OA participants compared to the control group in neutral and valgus, but not varus, and significantly reduced in women compared to men. A weak negative correlation was observed between the TDPM and stiffness estimates, suggesting that poorer proprioception was associated with less joint stiffness. CONCLUSION: While both joint stiffness and proprioception were reduced in the OA population, they were only weakly correlated. This suggests that other neurophysiologic factors play a larger role in the proprioceptive deficits in knee OA.