Does Knee Osteoarthritis Alter the Neuromuscular Responses to a Perturbation During Single Lower Limb Stance?

Clinical and Biomechanical Efficacies of Mechanical Perturbation Training After Anterior Cruciate Ligament Rupture

CONTEXT

Manual perturbation training improves knee functional performance and mitigates abnormal gait in patients with anterior cruciate ligament (ACL) rupture. However, manual perturbation training is time- and labor-intensive for therapists.

OBJECTIVE

To investigate whether perturbation training administered using a mechanical device can provide effects similar to manual training on clinical measures and knee biomechanics after ACL rupture.

DESIGN

Prospective cohort (therapeutic) study. A 2 × 2 analysis of variance was used for statistical analysis.

SETTING

A clinical and biomechanical laboratory.

PATIENTS

Eighteen level I/II patients with acute ACL ruptures participated in this preliminary study.

INTERVENTION

Nine patients received mechanical perturbation training on an automated mechanical device (mechanical group), and 9 patients received manual perturbation training (manual group).

OUTCOME MEASURES

Patients completed performance-based testing (quadriceps strength and single-legged hop tests), patient-reported questionnaires (Knee Outcome Survey-Activities of Daily Living Scale, Global Rating Score, and International Knee Documentation Committee 2000), and 3-dimensional gait analysis before (pretesting) and after (posttesting) training.

RESULTS

There was no significant group-by-time interaction found for all measures (P ≥ .18). Main effects of time were found for International Knee Documentation Committee 2000 (pretesting: 69.10 [10.95], posttesting: 75.14 [7.19]), knee excursion during weight-acceptance (pretesting: 16.01° [3.99°]; posttesting: 17.28° [3.99°]) and midstance (pretesting: 14.78° [4.13°]; posttesting: 16.92° [4.53°]) and external knee-flexion moment (pretesting: 0.43 [0.11] N m/kg/m; posttesting: 0.48 [0.11] N m/kg/m) (P ≤ .04). After accounting for pretesting groups' differences, the mechanical group scored significantly higher on triple hops (mechanical: 96.73% [6.65%]; manual: 84.97% [6.83%]) and 6-m timed hops (mechanical: 102.07% [9.50%]; manual: 91.21 [9.42%]) (P ≤ .047) compared with manual group.

CONCLUSION

The clinical significance of this study is the mechanical perturbation training produced effects similar to manual training, with both training methods were equally  effective at improving patients' perception of knee function and increasing knee excursion and external flexion moment during walking after acute ACL rupture. Mechanical perturbation training is a potential treatment to improve patients' functional and biomechanical outcomes after ACL rupture.

Exercise and osteoarthritis: cause and effects

Osteoarthritis (OA) is a common chronic joint condition predominantly affecting the knee, hip, and hand joints. Exercise plays a role in the development and treatment of OA but most of the literature in this area relates to knee OA. While studies indicate that exercise and physical activity have a generally positive effect on healthy cartilage metrics, depending upon the type of the activity and its intensity, the risk of OA development does appear to be moderately increased with sporting participation. In particular, joint injury associated with sports participation may be largely responsible for this increased risk of OA with sport. Various repetitive occupational tasks are also linked to greater likelihood of OA development. There are a number of physical impairments associated with OA including pain, muscle weakness and altered muscle function, reduced proprioception and postural control, joint instability, restricted range of motion, and lower aerobic fitness. These can result directly from the OA pathological process and/or indirectly as a result of factors such as pain, effusion, and reduced activity levels. These impairments and their underlying physiology are often targeted by exercise interventions and evidence generally shows that many of these can be modified by specific exercise. There is currently little clinical trial evidence to show that exercise can alter mechanical load and structural disease progression in those with established OA, although a number of impairments, that are amenable to change with exercise, appears to be associated with increased mechanical load and/or disease progression in longitudinal studies.

Individuals with medial knee osteoarthritis show neuromuscular adaptation when perturbed during walking despite functional and structural impairments

Neuromuscular control relies on sensory feedback that influences responses to changing external demands, and the normal response is for movement and muscle activation patterns to adapt to repeated perturbations. People with knee osteoarthritis (OA) are known to have pain, quadriceps weakness, and neuromotor deficits that could affect adaption to external perturbations. The aim of this study was to analyze neuromotor adaptation during walking in people with knee OA (n = 38) and controls (n = 23). Disability, quadriceps strength, joint space width, malalignment, and proprioception were assessed. Kinematic and EMG data were collected during undisturbed walking and during perturbations that caused lateral translation of the foot at initial contact. Knee excursions and EMG magnitudes were analyzed. Subjects with OA walked with less knee motion and higher muscle activation and had greater pain, limitations in function, quadriceps weakness, and malalignment, but no difference was observed in proprioception. Both groups showed increased EMG and decreased knee motion in response to the first perturbation, followed by progressively decreased EMG activity and increased knee motion during midstance over the first five perturbations, but no group differences were observed. Over 30 trials, EMG levels returned to those of normal walking. The results illustrate that people with knee OA respond similarly to healthy individuals when exposed to challenging perturbations during functional weight-bearing activities despite structural, functional, and neuromotor impairments. Mechanisms underlying the adaptive response in people with knee OA need further study.

Role of cognition and priming in interlimb generalization of adaptive control of gait stability

The authors examined the impact of (a) awareness of impending slip and (b) priming (to accelerate learning) on interlimb transfer of acquired stability control. Among the participants, 12 of 24 young individuals were not informed of 2 impending slips on the nontrained left-side (UNWARN), whereas the other 12 knew the exact timing and location of the 1st left slip (WARN) following 24 right-side slips, given to all participants while walking. Both groups reduced the backward loss of balance (BLOB) incidence from 100% on the first slip to 0% on 24th slip. The authors found significantly better transfer of the improved stability control in WARN than in UNWARN, resulting in a greater reduction in BLOB on the 1st left slip (55% vs. 92%, respectively). The priming was evident with no BLOB on the 2nd left slip versus 50% on the 2nd right slip. Thus, the interlimb generalization can be improved by cognition and evidenced in priming.

Can observational training substitute motor training in preventing backward balance loss after an unexpected slip during walking?

A person's awareness of potential slippery walking conditions induces a cautious gait pattern. The purposes of this study were to determine whether neuromechanical changes associated with such cognitive conditioning are sufficient to alter the outcome of a slip and whether the effects of such conditioning are comparable to those of motor training. Prior to their own first slip exposure, 18 young subjects watched videos and slides demonstrating where and how the slip would occur and how people adapted to repeated-slip exposure (observe). The outcomes of the first slip exposure experienced by another 16 subjects who did not receive any such information were used as controls (naïve). The latter subjects subsequently experienced an additional 23 slips and thus served in a dual-role as the motor training group (motor). Gait stability as measured against backward loss of balance (BLOB) was obtained for pre- and postslip instances. A protective step landing posterior to the slipping-limb identified each BLOB outcome. The observe group had a greater postslip stability and lower slip displacement and velocity than the naïve group. However, such effects were insufficient to prevent balance loss (100% BLOB). The motor group showed significantly better performance on the last training slip (0% BLOB) than did the observe group. The results indicated that updating the cognitive centers of the CNS with awareness and perceptual knowledge through observational training can yield tangible benefits. Nonetheless observation could not replace the task-specific motor training that adaptively updated the internal representations of stability limits for prevention of BLOB.