Alasdair R. Dempsey

Changing Sidestep Cutting Technique Reduces Knee Valgus Loading

Background Common lower limb postures have been found when noncontact anterior cruciate ligament (ACL) injuries occur during sidestep cutting tasks. These same postures have been linked to knee loadings known to stress the ACL. Hypothesis Whole body technique modification would reduce knee loading. Study Design Controlled laboratory study. Methods Experienced team sport athletes were recruited for whole body sidestep cutting technique modification. Before and after a 6-week technique modification training, participants performed sidestep cutting tasks while ground-reaction force and motion data were collected. A kinematic and inverse dynamics model was used to calculate 3-dimensional knee loading during sidestep cutting. Results At initial foot contact, the participants placed their stance foot closer to the body’s midline and held their torso more upright, in line with the aims of the technique modification training. This was accompanied by significantly lower peak valgus moments in the weight acceptance phase of stance. Both postural changes were correlated with the change in peak valgus moment. Conclusion Whole body sidestep cutting technique modification resulted in reduced knee loading. Clinical Relevance Implementation of whole body technique modification may produce effective ACL injury prevention programs in sports involving sidestep cutting.

An anterior cruciate ligament injury prevention framework: incorporating the recent evidence.

Anterior cruciate ligament (ACL) injury rates have increased by ∼50% over the last 10 years. These figures suggest that ACL focused research has not been effective in reducing injury rates among community level athletes. Training protocols designed to reduce ACL injury rates have been both effective (n = 3) and ineffective (n = 7). Although a rationale for the use of exercise to reduce ACL injuries is established, the mechanisms by which they act are relatively unknown. This article provides an injury prevention framework specific to noncontact ACL injuries and the design of prophylactic training protocols. It is also apparent that feedback within this framework is needed to determine how biomechanically relevant risk factors like peak joint loading and muscular support are influenced following training. It is by identifying these links that more effective ACL injury prevention training programs can be developed, and, in turn, lead to reduced ACL injury rates in the future.

Changes in knee joint biomechanics following balance and technique training and a season of Australian football

Purpose Determine if balance and technique training (BTT) implemented adjunct to normal Australian football (AF) training reduces external knee loading during sidestepping. Additionally, the authors determined if an athletes knee joint kinematics and kinetics change over a season of AF. Methodology Eight amateur-level AF clubs (n=1,001 males) volunteered to participate in either 28 weeks of BTT or a ‘sham’ training (ST) adjunct to their normal preseason and regular training. A subset of 34 athletes (BTT, n=20; ST, n=14) were recruited for biomechanical testing in weeks 1–7 and 18–25 of the 28-week training intervention. During biomechanical testing, participants completed a series running, preplanned (PpSS) and unplanned sidestepping (UnSS) tasks. A linear mixed model (α=0.05) was used to determine if knee kinematics and peak moments during PpSS and UnSS were influenced by BTT and/or a season of AF. Results Both training groups significantly (p=0.025) decreased their peak internal-rotation knee moments during PpSS, and significantly (p=0.022) increased their peak valgus knee moments during UnSS following their respective training interventions. Conclusions BTT was not effective in changing an athletes knee joint biomechanics during sidestepping when conducted in ‘real-world’ training environments. Following normal AF training, the players had different changes to their knee joint biomechanics during both preplanned and unplanned sidestepping. When performing an unplanned sidestepping task in the latter half of a playing season, athletes are at an increased risk of ACL injury. The authors therefore recommend both sidestepping tasks are performed during biomechanical testing when assessing the effectiveness of prophylactic training protocols.

Whole body kinematics and knee moments that occur during an overhead catch and landing task in sport

BACKGROUND Athletes suffering an anterior cruciate ligament injury tend to exhibit similar body postures that in sidestep cutting are associated with increased knee moments. This relationship, however, has not been investigated in landing. Catching a ball in different overhead positions may affect landing postures and knee joint moments. This study investigated these possible relationships. It was anticipated that some joint postures would be associated increased knee loads during the landing task. METHODS Twenty-five healthy male team sports athletes performed four variations of a landing task. Full body kinematics were identified at initial contact. Peak flexion, valgus and internal rotation moments at the knee, measured during early landing, were normalized to mass and height and statistically compared. Intra-participant correlations were performed between all kinematics and each moment. Mean slopes for each correlation were used to identify the existence of relationships between full body kinematics and knee joint moments. Findings Landing after an overhead catch when the ball moved towards a players support leg resulted in increased peak valgus moments. These increased valgus moments were correlated with increased knee flexion, hip flexion, and torso lean, as well as torso rotation towards the support leg, and foot and knee external rotation. Increased internal rotation moments were correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg. Interpretation Learning to land with techniques that do not reflect postures associated with high knee moments may reduce an athletes risk of non-contact anterior cruciate ligament injury.

A longitudinal study of strength and gait after arthroscopic partial meniscectomy

PURPOSE Individuals after arthroscopic partial meniscectomy (APM) are at increased risk of developing knee osteoarthritis (OA). Knee muscle weakness and a higher external knee adduction moment (KAM) are potential risk factors for knee OA. This exploratory longitudinal study assessed these risk factors at baseline in an APM group (3 months after surgery) and control group, and again 2 yrs later (follow-up). METHODS Eighty-two participants with medial APM and 38 healthy controls were assessed at baseline, with 66 (79%) and 23 (61%), respectively, retested at follow-up. Outcome measures included isokinetic knee muscle strength and medial knee joint load inferred through indices of the KAM during normal and fast-pace walking. RESULTS Knee muscle strength was reduced by 14%-16% in the APM leg compared with controls at baseline (P ≤ 0.006). However, strength increased in the APM leg over the 2 yrs such that there were no differences compared with controls at follow-up. KAM impulse was at least 20% higher for the APM group (both legs) when compared with controls at baseline and remained similarly higher 2 yrs later (P ≤ 0.022). At baseline peak, KAM was 18% higher in the APM leg as compared with controls only during fast-pace walking (P = 0.013). The peak KAM increased over the 2 yrs in the APM leg by 8%-9% (P ≤ 0.032), although there were no differences in change in KAM between the APM leg and controls. CONCLUSION This study found that although knee muscle strength improved, dynamic medial joint load increased over the 2 yrs after APM surgery. These findings may aid in developing therapeutic interventions aimed to prevent or delay the onset of knee OA after APM.

Effect of Ankle Taping on Knee and Ankle Joint Biomechanics in Sporting Tasks

INTRODUCTION Prophylactic taping is commonly used to prevent ankle injuries during sports. However, unnatural constraint of the ankle joint may increase the risk of injury to proximal joints such as the knee. The association between ankle taping and knee joint loading during open sporting tasks has not been quantified. This research aimed to measure changes in knee and ankle kinetics and kinematics during dynamic athletic activities undertaken with and without ankle taping. METHODS A kinematic and inverse dynamics model was used to determine ankle and knee joint motion and loading in 22 healthy male participants undertaking running and sidestepping tasks. Both tasks were randomized to planned and unplanned conditions and undertaken with and without the use of ankle tape. RESULTS At the knee, peak internal rotation moments (P < 0.001) and peak varus moments (P < 0.05) were significantly reduced during all running and sidestepping trials (planned and unplanned) when undertaken with ankle tape. Internal rotation impulse (P < 0.001) was reduced for sidestepping tasks. Varus impulse during unplanned sidestepping maneuvers (P = 0.04) was reduced with the use of ankle tape. However, there was a trend toward increased valgus moments and impulse for planned sidestepping trials undertaken with ankle tape(P = 0.056). Taping reduced the range of motion at the ankle in all three planes (P < 0.05). Peak inversion (P < 0.001) was reduced for running trials only. Average eversion and peak dorsiflexion moments were significantly reduced in sidestepping tasks by use of taping. CONCLUSIONS By limiting motion at the ankle, taping increased mechanical stability at this joint. Ankle taping also provided protective benefits to the knee via reduced internal rotation moments and varus impulses during both planned and unplanned maneuvers. Medial collateral and anterior cruciate ligament injuries may, however, occur through increased valgus impulse during sidestepping undertaken with ankle tape.

Does Action Observation Training With Immediate Physical Practice Improve Hemiparetic Upper-Limb Function in Chronic Stroke?

Background. The mirror neuron network provides a neural mechanism to prime the motor system through action observation in stroke survivors. Objective. To examine whether action observation training with immediate physical practice improves upper-limb function in chronic stroke. Methods. In a within-subject design, 14 chronic stroke survivors were assessed at baseline, then participated in 2 weeks of relaxation-sham plus physical practice (control) and reassessed. Thereafter, they participated in 2 weeks of action observation training coupled with immediate physical practice (intervention), followed by a final assessment. Duration of each action observation video sequence (priming exposure) was 30 s followed immediately by practice of the observed motor skill. Results. There were significant improvements in control and intervention phases on primary outcome measures—Upper Extremity Fugl-Meyer Motor Assessment (FMA) and Functional Test of the Hemiparetic Upper Extremity (FTHUE)—as well as secondary outcome measures of self-perceptions of arm use. Gains in the primary outcomes were greater during the intervention phase (action observation + physical practice; FMA, 10.64; FTHUE level, 0.79, and tasks, 1.57) than during the control phase (relaxation-sham plus physical practice; FMA, 6.64; FTHUE level, 0.43, and tasks, 1.00). Interviews with participants highlighted the added value of watching an actor perform the movement before physically attempting to perform the action. Conclusions. This study provides preliminary evidence of the additive value of action observation plus physical practice over relaxation-sham plus physical practice. There appears to be capacity for further recovery of upper-limb function in chronic stroke that persists at least in the short term.

Individual differences in highly skilled visual perceptual-motor striking skill

Expertise studies into visual perceptual-motor skills have mainly focused their investigation upon group comparisons rather than individual comparisons. This study investigated the pick-up of visual information to time weight transfer and bat kinematics within an exemplar group of striking sport experts using an in situ temporal occlusion paradigm. Highly skilled cricket batsmen faced bowlers and attempted to strike delivered balls, whilst their vision was either temporally occluded through occlusion glasses prior to ball bounce or not occluded (control condition). A chronometric analysis was conducted on trials in the occlusion condition to quantify the pick-up of visual information to time biomechanical variables. Results indicated that initiation of weight transfer and bat downswing, as well as bat downswing completion, was significantly different between some individual batsmen. No significant difference was found between individual batsmen for time of weight transfer completion. Unexpectedly, it was found that achievement of the goal to strike delivered balls, that is, the frequency of bat-ball contacts was not significantly different between batsmen. Collectively, the findings indicate that individual differences exist in the coordination pattern of a complex whole body visual perceptual-motor skill, but these different patterns are used to achieve a similar outcome, which is known as motor equivalence.

Trabecular bone texture detected by plain radiography and variance orientation transform method is different between knees with and without cartilage defects

The objective of this work is to evaluate differences in trabecular bone (TB) texture between subjects with and without tibiofemoral cartilage defects using a variance orientation transform (VOT) method. A case–control study was performed in subjects without radiographic knee osteoarthritis (OA) (K&L grade <2) matched on sex, BMI, age, knee compartment, and meniscectomy where cases (n = 28) had cartilage defects (grade ≥2) and controls (n = 28) had no cartilage defects (grade <2). Cartilage defects were assessed from MRI using validated methods. The VOT was applied to TB regions selected on medial and lateral compartments in knee X‐rays and fractal signatures (FS) in the horizontal (FSH) and vertical (FSV) directions, and along the roughest part of TB (FSSta) and texture aspect ratio signatures (StrS), at different trabecular image sizes (0.30–0.70 mm) were calculated. Compared with controls, FSV for cases were higher (p < 0.011) at image sizes 0.30–0.40 mm and 0.45–0.55 mm in the medial compartment. In the lateral compartment, FSH and FSSta for cases were higher (p < 0.028) than those for controls at 0.30–0.40 mm and 0.45–0.55 mm, while FSV was higher (p < 0.02) at 0.30–0.40 mm. TB texture roughness was greater in subjects with cartilage defects than in subjects without, suggesting thinning and fenestration of TB occur early in OA and that the VOT identifies changes in TB in knees with early cartilage damage. No differences in StrS (p > 0.05) were found.

Do moments and strength predict cartilage changes after partial meniscectomy

PURPOSE Higher knee load and quadriceps weakness are potential factors involved in the pathogenesis of knee osteoarthritis after arthroscopic partial meniscectomy (APM). In people following APM, this study evaluated the association between external knee joint moments and quadriceps strength and 2-yr change in indices of cartilage integrity in the medial tibiofemoral compartment and patella. METHODS Seventy people with medial APM were assessed 3 months after APM (baseline) and reassessed 2 yr later (follow-up). At baseline, isokinetic quadriceps strength and the external knee adduction moment (peak and impulse) and knee flexion moment (peak) during walking were assessed. Magnetic resonance imaging was used to assess cartilage (cartilage volume and cartilage defects) in the medial tibial compartment and patella at baseline and follow-up. RESULTS Increased peak knee adduction moment during fast-pace walking at baseline was associated with onset or deterioration of medial tibiofemoral cartilage defects (OR, 2.06; 95% CI, 1.03-4.12; P = 0.042) over 2 yr. Increased peak knee flexion moment during normal-pace walking at baseline was associated with loss of patellar cartilage volume over 2 yr (β = -0.24; 95% CI, -0.47 to -0.01; P = 0.04). No significant association was observed for quadriceps strength. CONCLUSION In middle-age adults, a higher peak knee adduction moment and peak knee flexion moment at 3 months after medial APM may be associated with adverse structural changes at the medial tibia and patella over the subsequent 2 yr. These preliminary findings warrant further investigation as interventions aimed at reducing these moments may be designed if appropriate.