Increased pain sensitivity but normal function of exercise induced analgesia in hip and knee osteoarthritis--treatment effects of neuromuscular exercise and total joint replacement.

OBJECTIVE: To assess exercise induced analgesia (EIA) and pain sensitivity in hip and knee osteoarthritis (OA) and to study the effects of neuromuscular exercise and surgery on these parameters. DESIGN: The dataset consisted of knee (n = 66) and hip (n = 47) OA patients assigned for total joint replacement at Lund University Hospital undergoing pre-operative neuromuscular exercise and 43 matched controls. Sensitivity to pressure pain was assessed by pressure algometry at 10 sites. Subjects were then instructed to perform a standardized static knee extension. Pressure pain thresholds (PPTs) were assessed at the contracting quadriceps muscle (Q) and at the resting deltoid muscle (D) before and during contraction. The relative increase in PPTs during contraction was taken as a measure of localized (Q) or generalized (D) EIA. Patients were assessed at baseline, following on average 12 weeks of neuromuscular exercise and 3 months following surgery. RESULTS: We found a normal function of EIA in OA patients at baseline. Previous studies have reported beneficial effects of physical exercise on pain modulation in healthy subjects. However, no treatment effects on EIA were seen in OA patients despite the increase in muscle strength following neuromuscular exercise and reduced pain following surgery. Compared to controls, OA patients had increased pain sensitivity and no beneficial effects on pain sensitivity were seen following treatment. CONCLUSIONS: To our knowledge, this is the first study of EIA in OA patients. Despite increased pain sensitivity, OA patients had a normal function of EIA.

Brain activity in predictive sensorimotor control for landings: an EEG pilot study.

Landing from a jump is related to predictive sensorimotor control. Frontal, central and parietal brain areas are known to play a role in this process based on online sensory feedback. This can be measured by EEG. However, there is only limited knowledge about brain activity during predictive preparation for drop landings (DL). The purpose is to demonstrate changes in brain activity in preparation for DL in different conditions. After resting, 10 athletes performed a series of DLs and were asked to concentrate on the landing preparation for 10 s before an auditory signal required them to drop land from a 30 cm platform. This task was executed before and after a standardized fatigue protocol. EEG spectral power was calculated during DL preparation. Frontal Theta power was increased during preparation compared to rest. Parietal Alpha-2 power demonstrated higher values in preparation after fatigue condition while lower limb kinematics remained unchanged. Cortical activity in frontal and parietal brain areas is sensitive for predictive sensorimotor control of drop landings. Frontal Theta power demonstrates an increase and is related to higher attentional control. In a fatigued condition the parietal Alpha-2 power increase might be related to a deactivation in the somatosensory brain areas.

Acute Neuromuscular Activity in Selected Injury Prevention Exercises with App-Based versus Personal On-Site Instruction: A Randomized Cross-Sectional Study.

INTRODUCTION: A significant step towards sport-related injury prevention is the introduction of easily accessible smartphone applications (apps). However, it is unknown whether this type of app-based instruction facilitates similar acute neuromuscular and biomechanical characteristics of the preventive exercises as achieved when instructed on-site by an expert. Thus, the aim was to evaluate acute neuromuscular characteristics observed during a single bout of selected lower extremity injury preventive exercises instructed by an on-screen app versus on-site individual instruction provided by a physiotherapist. METHODS: In a cross-sectional study design, 47 female football and handball players were randomly assigned to receive app instruction (APP group) or on-site instruction provided by a physiotherapist (PHY group) while performing five lower extremity injury preventive exercises. The exercises performed comprised (1) one-legged balance on Airex, (2) vertical drop jump, (3) one-legged horizontal jump onto floor, (4) one-legged horizontal jump onto Airex, and (5) two-hand Kettlebell Swing. Primary outcome was hamstring (biceps femoris and semitendinosus) muscle activity. Secondary outcomes were quadriceps (vastus lateralis and medialis) muscle activity, as well as hip and knee joint angles. Muscle activity was monitored by surface electromyography (EMG) and normalized to the peak amplitude obtained during a maximal voluntary isometric contraction (MVC). Hip and knee joint angles were recorded by a 3D motion analysis system. A linear mixed model was used to evaluate the differences between experimental conditions for each outcome variable. RESULTS: Medial hamstring (semitendinosus) muscle activity was significantly higher during one-legged jump onto Airex (17 percentage points (95% CI 7 to 27)) and Kettlebell Swing (19 percentage points (95% CI 2 to 36)) in the PHY group than the APP group. Likewise, the PHY group demonstrated 18 percentage points (95% CI 1 to 35) and 19 percentage points (95% CI 0 to 38), greater lateral quadriceps muscle (vastus lateralis) activity during one-legged jump onto floor and one-legged jump onto Airex, respectively, compared with that of the APP group. CONCLUSIONS: Complex exercises, i.e., Kettlebell Swing and one-legged jump onto Airex, are characterized by lower neuromuscular activity when using app-based instructions compared with on-site instruction provided by a physiotherapist. However, the effectiveness of app-based instruction versus on-site individual instruction in injury prevention interventions remains to be investigated in future longitudinally studies.

Factors affecting knee abduction during weight-bearing activities in individuals with anterior cruciate ligament reconstruction.

OBJECTIVE: To investigate if muscle strength and muscle activation patterns are associated with increased knee abduction during two functional tasks, commonly used in rehabilitation for individuals with anterior cruciate ligament reconstruction (ACLR). DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: 24 women and 29 men approximately 7 months after ACLR. MAIN OUTCOME MEASURES: Isometric peak torque of the trunk and lower extremity muscles were determined during maximal voluntary contractions. Trunk and lower extremity average muscle activation amplitude and peak knee abduction were evaluated during the single-leg squat (SLS) and the single-leg hop for distance (SLHD) for the injured side. Separate backward regressions were performed for men and women. RESULTS: In women, lower knee flexion and extension strength were associated with greater peak knee abduction during the SLS (B = 4.63-18.26, p ≤ 0.036); lower knee flexion strength and iliocostalis activation on the non-injured side were associated with greater peak knee abduction during the SLHD (B = 0.60-20.48, p ≤ 0.043). No associations between muscle function and peak knee abduction were found in men. CONCLUSIONS: Muscle function may contribute differently to knee abduction in men and women after ACLR. This should be considered when designing rehabilitation programs to reduce knee abduction in these patients.

Influence of supervised and nonsupervised training on postural control after an acute anterior cruciate ligament rupture: a three-year longitudinal prospective study.

STUDY DESIGN: Prospective randomized longitudinal clinical trial with matched controls. OBJECTIVES: To investigate the long-term effect of training on postural control and extremity function after an acute anterior cruciate ligament (ACL) injury. BACKGROUND: ACL injuries may cause severe problems with recurrent giving way of the knee and reduced functional capacity. The effect of an acute ACL injury and the effect of various training programs on postural control, as well as the relation between postural control and extremity function after such an injury, have not been studied longitudinally. METHODS: Sixty-three consecutive patients, 35 men and 28 women (median age 24 years, quartiles 19-33 years), with an acute nonoperated ACL injury, randomized to neuromuscular supervised or self-monitored training, were examined with stabilometry (amplitude and average speed of center of pressure movements) and a one-leg hop test for distance after 6 weeks (stabilometry only), and after 3, 12, and 36 months, and were compared to a control group. RESULTS: Regardless of treatment, center of pressure amplitude was persistently higher in both the injured and uninjured legs during the 3-year follow-up, but average speed was less affected or unaffected compared to the control group. The one-leg hop had normalized in the neuromuscular group at the 12-month follow-up, but was shorter in both legs throughout the 3-year period in the self-monitored group. The median value (quartiles) for injured/uninjured legs at 3 months was 150 cm (120-174 cm)/177 cm (140-199 cm), at 12 months was 174 cm (140-200 cm)/180 cm (150-202 cm), and at 36 months was 172 cm (146-200 cm)/178 cm (150-200 cm) in the self-monitored group, compared to the control group (median 186 cm, quartiles 177-216 cm). CONCLUSIONS: The higher center of pressure amplitude in both legs over the 3-year period indicate persistently impaired postural control in single-limb stance. However, functional performance, as measured with the one-leg hop test, was restored by neuromuscular training, but not by self-monitored training.

Review of knee proprioception and the relation to extremity function after an anterior cruciate ligament rupture.

Several tests of human conscious knee proprioception have been described, but there is no consensus or reference standard established. Difficulties remain in the separation of information originating from muscles, tendons, and joints, and the tests cannot discriminate between loss of afferent signals or altered activity in the remaining receptors. There is convincing evidence from several descriptive studies that the afferent information is altered after a knee ligament injury and severely disturbed in some patients with anterior cruciate ligament (ACL) injuries. However, an inherent inferior proprioceptive ability may also exist in some individuals, which makes them vulnerable to injuries. The deficits in proprioception have mostly been studied and related to the consciously registered sense, whereas the extent of possible disturbances of the unconscious or reflectory mechanisms is largely unknown. The latter may, at least from a theoretical point of view, be predominantly contributing to the overall afferent regulation, and a possibility for major defects thus exists, since there is no knowledge of the quantified relation between the conscious and unconscious part. The clinical importance of the altered afferent information has not been evaluated properly, and the role of proprioception that contributes to function has yet to be investigated. A higher physiological sensitivity to detecting a passive joint motion closer to full extension has been found both experimentally and clinically, which may protect the joint due to the close proximity to the limit of joint motion. Proprioception has been found to have a relation to subjective knee function, and patients with symptomatic ACL deficiency seem to have larger deficits than asymptomatic individuals. Little is known about whether training can restore defects in sensory information or by which mechanisms possible compensatory pathways are established. In rehabilitation, each patient must, however, create muscle strength, alertness, and stiffness in harmony with the disturbed mechanics of the knee, which are present both after nonoperative treatment of the ACL and after a reconstruction of the ACL.

Clinical measurements of proprioception, muscle strength and laxity in relation to function in the ACL-injured knee.

A knee injury with anterior cruciate ligament (ACL) rupture may cause deficits in proprioception, increased laxity and decreased muscle strength. Although it may be common knowledge that these factors affect knee function, only a few studies have been performed where this has been investigated in the clinical situation, and the results are not conclusive. The purpose of this study was therefore to investigate how and to what extent proprioception, laxity and strength affect knee joint function and evaluate if the methods commonly used for estimating these factors clinically seem to be relevant. The study encompassed 36 patients with ACL deficiency. A single-leg hop test for distance and subjective rating of knee function were defined as dependent variables and analyzed separately in stepwise linear regression models where proprioception, knee joint laxity, hamstrings and quadriceps strength, age and sex were defined as independent variables. Higher threshold values (poorer proprioception), increased side-to-side difference of anterior laxity and poorer strength significantly predicted shorter length of the hop test. Higher rating of subjective function corresponded to female gender, lesser side-to-side difference of anterior laxity and better proprioception.

Stabilometry and one-leg hop test have high test-retest reliability.

The purpose of this study was to investigate the reliability of repeated measurements and a possible learning or tiring process in single-limb stabilometry and one-leg hop test. An additional purpose was to study the correlation between different stabilometric variables. Seventy-five healthy subjects were examined twice with a median interval of 7 d, and with three consecutive measurements on each occasion. Single-limb stabilometry and one-leg hop test were found to have high reliability (ICC r = 0.68-0.83 and 0.96, respectively). The correlation between consecutive measurements was acceptable to high in stabilometry (r = 0.42-0.90, P = 0.002-P < 0.001) and high in the one-leg hop test (r = 0.91-0.97, P < 0.001). A learning process over time was observed. The correlation between the stabilometric variables was high (r = 0.73-0.95, P < 0.001).

Individual factors affecting stabilometry and one-leg hop test in 75 healthy subjects, aged 15-44 years.

The aims of this study were: 1) to investigate whether single-limb stabilometry and a one-leg hop test are influenced by age, sex, height, weight or activity level in healthy subjects, 2) to examine possible differences between the right and the left leg, 3) to determine Limb Symmetry Index (LSI) values, and 4) to study the relation between the stabilometric variables, that is, average speed (AS) and amplitude of center of pressure (CP) movements. Seventy-five healthy subjects (39 women) were studied, with a mean age of 29.5 years (SD 8.2, range 15-44), mean height 175 cm (SD 8.6, range 155-194), mean weight 67.8 kg (SD 9.7, range 50-90) and median value 8 (quartiles 8-9, range 7-10) on a 1-10 activity-level scale. AS was higher among the men compared to the women and increased with increasing age. The females hopped shorter distances than the males. The hop distance decreased with increasing age among the women. Height, weight and activity level within the actual range had no significant influence on stabilometric or hop-test values. When comparing patients with healthy subjects, they should be matched according to sex and age, with an age difference of less than 10 years within pairs.