Words matter: Effects of instructional cues on pressure pain threshold values in healthy people.

BACKGROUND: Pressure pain threshold (PPT) measurements require standardised verbal instructional cues to ensure that the increasing pressure is stopped at the correct time consistently. This study aimed to compare how PPT values and their test-retest reliability were affected by different instructional cues. METHODS: At two separate sessions, two PPT measurements were taken at the anterior knee for each of four different instructional cues: the cue of the German Neuropathic Research Network instructions ('DFNS'), the point where pressure first feels uncomfortable ('Uncomfortable'), 3/10 on the numerical pain rating scale ('3NPRS'), and where pain relates to an image from the pictorial-enhanced NPRS scale ('Pictorial'). Linear mixed modeling was used to quantify differences between pairs of instructional cues. Test-retest reliability was estimated using intraclass correlation coefficients (ICC[2,1] and ICC[2,k]). RESULTS: Twenty participants were recruited. The cue resulting in greatest PPT value was DFNS (394.32 kPa, 95%CI [286.32 to 543.06]), followed by Pictorial (342.49 kPa, 95%CI [248.68 to 471.68]), then Uncomfortable (311.85 kPa, 95%CI [226.43 to 429.48]), and lastly 3NPRS (289.78 kPa, 95%CI [210.41 to 399.09]). Five of six pairwise contrasts were statistically significant. Regardless of the cues, the point estimates of ICC (2,1) ranged from 0.80 to 0.86, and the ICC (2,k) values ranged from 0.89 to 0.93. No statistically significant differences were found between any pairwise contrasts of reliability indices. CONCLUSION: Words matter when instructing people when to stop testing in pressure algometry. Clinicians should use the same instructional cue when assessing pain thresholds to ensure reliability.

Using wearable technology data to explain recreational running injury: A prospective longitudinal feasibility study.

OBJECTIVES: Investigate 1) if collecting and analysing wristwatch inertial measurement unit (IMU) and global positioning system (GPS) data using a commercially-available training platform was feasible in recreational runners and 2) which variables were associated with subsequent injury. DESIGN: Prospective longitudinal cohort. PARTICIPANTS: Healthy recreational runners. MAIN OUTCOME MEASURES: We set a priori feasibility thresholds for recruitment (maximum six-months), acceptance (minimum 80%), adherence (minimum 70%), and data collection (minimum 80%). Participants completed three patient-reported outcome measures (PROMS) detailing their psychological health, sleep quality, and intrinsic motivation to run. We extracted baseline anthropometric, biomechanical, metabolic, and training load data from their IMU/GPS wristwatch for analysis. Participants completed a weekly injury status surveillance questionnaire over the next 12-weeks. Feasibility outcomes were analysed descriptively and injured versus non-injured group differences with 95% confidence intervals were calculated for PROM/IMU/GPS data. RESULTS: 149 participants consented; 86 participants completed (55 men, 31 women); 21 developed an injury (0.46 injuries/1000km). Feasibility outcomes were satisfied (recruitment = 47 days; acceptance = 133/149 [89%]; adherence = 93/133 [70%]; data collection = 86/93 [92%]). Acute load by calculated effort was associated with subsequent injury (mean difference -562.14, 95% CI -1019.42, -21.53). CONCLUSION: Collecting and analysing wristwatch IMU/GPS data using a commercially-available training platform was feasible in recreational runners.

The feasibility, safety, and efficacy of lower limb garment-integrated blood flow restriction training in healthy adults.

OBJECTIVES: Explore the feasibility of lower-limb garment-integrated BFR-training. DESIGN: Observational study. SETTING: Human performance laboratory. PARTICIPANTS: Healthy males with no experience of BFR-training. MAIN OUTCOME MEASURES: Feasibility was determined by a priori thresholds for recruitment, adherence, and data collection. Safety was determined by measuring BFR torniquet pressure and the incidence of side effects. Efficacy was determined by measuring body anthropometry and knee isokinetic dynamometry. Feasibility and safety outcomes were reported descriptively or as a proportion with 95% confidence intervals (95% CI), with mean change, 95% CIs, and effect sizes for efficacy outcomes. RESULTS: Twelve participants (mean age 24.8 years [6.5]) were successfully recruited; 11 completed the study. 134/136 sessions were completed (adherence = 98.5%) and 100% of data were collected. There was one event of excessive pain during exercise (0.7%, 95% CI 0.0%, 4.0%), two events of excessive pain post-exercise (1.5%, 95% CI 0.4%, 5.5%), and one event of persistent paraesthesia post-exercise (0.7%, 95% CI 0.0%, 4.0%). Mean maximal BFR torniquet pressure was <200 mmHg. We observed an increase in knee extension peak torque (mean change 12.4 Nm), but no notable changes in body anthropometry. CONCLUSIONS: Lower-limb garment-integrated BFR-training is feasible, has no signal of important harm, and could be used independently.

Kinematic and Kinetic Gait Characteristics in People with Patellofemoral Pain: A Systematic Review and Meta-analysis.

BACKGROUND: Patellofemoral pain (PFP) is a prevalent knee condition with many proposed biomechanically orientated etiological factors and treatments. OBJECTIVE: We aimed to systematically review and synthesize the evidence for biomechanical variables (spatiotemporal, kinematic, kinetic) during walking and running in people with PFP compared with pain-free controls, and determine if biomechanical variables contribute to the development of PFP. DESIGN: Systematic review and meta-analysis. DATA SOURCES: We searched Medline, CINAHL, SPORTDiscus, Embase, and Web of Science from inception to October 2021. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: All study designs (prospective, case-control [± interventional component, provided pre-intervention data were reported for both groups], cross-sectional) comparing spatiotemporal, kinematic, and/or kinetic variables during walking and/or running between people with and without PFP. RESULTS: We identified 55 studies involving 1300 people with PFP and 1393 pain-free controls. Overall pooled analysis identified that people with PFP had slower gait velocity [moderate evidence, standardized mean difference (SMD) - 0.50, 95% confidence interval (CI) - 0.72, - 0.27], lower cadence (limited evidence, SMD - 0.43, 95% CI - 0.74, - 0.12), and shorter stride length (limited evidence, SMD - 0.46, 95% CI - 0.80, - 0.12). People with PFP also had greater peak contralateral pelvic drop (moderate evidence, SMD - 0.46, 95% CI - 0.90, - 0.03), smaller peak knee flexion angles (moderate evidence, SMD - 0.30, 95% CI - 0.52, - 0.08), and smaller peak knee extension moments (limited evidence, SMD - 0.41, 95% CI - 0.75, - 0.07) compared with controls. Females with PFP had greater peak hip flexion (moderate evidence, SMD 0.83, 95% CI 0.30, 1.36) and rearfoot eversion (limited evidence, SMD 0.59, 95% CI 0.03, 1.14) angles compared to pain-free females. No significant between-group differences were identified for all other biomechanical variables. Data pooling was not possible for prospective studies. CONCLUSION: A limited number of biomechanical differences exist when comparing people with and without PFP, mostly characterized by small-to-moderate effect sizes. People with PFP ambulate slower, with lower cadence and a shortened stride length, greater contralateral pelvic drop, and lower knee flexion angles and knee extension moments. It is unclear whether these features are present prior to PFP onset or occur as pain-compensatory movement strategies given the lack of prospective data. TRIAL REGISTRATION: PROSPERO # CRD42019080241.

Gait Retraining as an Intervention for Patellofemoral Pain.

PURPOSE OF REVIEW: Movement retraining in rehabilitation is the process by which a motor program is changed with the overall goal of reducing pain or injury risk. Movement retraining is an important component of interventions to address patellofemoral pain. The purpose of this paper is to review the methods and results of current retraining studies that are aimed at reducing symptoms of patellofemoral pain. RECENT FINDINGS: The majority of studies reviewed demonstrated some improvement in patellofemoral pain symptoms and overall function. However, the degree of improvement as well as the persistence of improvement over time varied between studies. The greatest pain reduction and persistent changes were noted in those studies that incorporated a faded feedback design including between 8 and 18 sessions over 2-6 weeks, typically 3-4 sessions per week. Additionally, dosage in these studies increased to 30-45 min during later sessions, resulting in 177-196 total minutes of retraining. In contrast, pain reductions and persistence of changes were the least in studies where overall retraining volume was low and feedback was either absent or continual. Faulty movement patterns have been associated with patellofemoral pain. Studies have shown that strengthening alone does not alter these patterns, and that addressing the motor program is needed to effect these changes. Based upon the studies reviewed here, retraining faulty patterns, when present, appears to play a significant role in addressing patellofemoral pain. Therefore, movement retraining, while adhering to basic motor control principles, should be part of a therapist's intervention skillset when treating patients with PFP.

Is markerless, smart phone recorded two-dimensional video a clinically useful measure of relevant lower limb kinematics in runners with patellofemoral pain? A validity and reliability study.

OBJECTIVES: Investigate the validity and reliability of markerless, smart phone collected, two-dimensional (2D) video, analysed using the 'Hudl technique' application, compared to three-dimensional (3D) kinematics during running, in participants with patellofemoral pain (PFP). DESIGN: Validity/reliability study. SETTING: Biomechanics laboratory. PARTICIPANTS: Males/females with PFP (n = 21, 10 males, 11 females, age 32.1 months [±12.9]). MAIN OUTCOME MEASURES: Manually synchronised 2D and 3D measurement of peak hip adduction (HADD) and peak knee flexion (KFLEX) during running. RESULTS: 2D and 3D measures of peak KFLEX (p = 0.02, d = 1.13), but not peak HADD (p = 0.25, d = -0.27), differed significantly. Poor validity was identified for 2D measurement of peak HADD (ICC 0.06, 95% CI -0.35, 0.47) and peak KFLEX ICC 0.42, 95% CI (-0.10, 0.75). Moderate intra-rater reliability was identified for both variables (ICC 0.61-65), alongside moderate inter-rater reliability for peak KFLEX (ICC 0.71) and poor inter-rater reliability for peak HADD (ICC 0.31). CONCLUSIONS: Measurement of peak HADD and KFLEX in runners with PFP using markerless, smart phone collected 2D video, analysed using the Hudl technique Application is invalid, with poor to moderate reliability. Investigation of alternate 2D video approaches to increase precision is warranted. At present, 2D video analysis of running using Hudl Technique cannot be advocated.

Increased hip adduction during running is associated with patellofemoral pain and differs between males and females: A case-control study.

Patellofemoral pain is common amongst recreational runners and associated with altered running kinematics. However, it is currently unclear how sex may influence kinematic differences previously reported in runners with patellofemoral pain. This case-control study aimed to evaluate lower limb kinematics in males and females with and without patellofemoral pain during running. Lower limb 3D kinematics were assessed in 20 runners with patellofemoral pain (11 females, 9 males) and 20 asymptomatic runners (11 females, 9 males) during a 3 km treadmill run. Variables of interest included peak hip adduction, internal rotation and flexion angles; and peak knee flexion angle, given their previously reported association with patellofemoral pain. Age, height, mass, weekly run distance and step rate were not significantly different between groups. Mixed-sex runners with patellofemoral pain were found to run with a significantly greater peak hip adduction angle (mean difference = 4.9°, d = 0.91, 95% CI 1.4-8.2, p = 0.01) when compared to matched controls, but analyses for all other kinematic variables were non-significant. Females with patellofemoral pain ran with a significantly greater peak hip adduction angle compared to female controls (mean difference = 6.6°, p = 0.02, F = 3.41, 95% CI 0.4-12.8). Analyses for all other kinematic variables between groups (males and females with/without PFP) were non-significant. Differences in peak hip adduction between those with and without patellofemoral pain during running appear to be driven by females. This potentially highlights different kinematic treatment targets between males and females. Future research is encouraged to report lower limb kinematic variables in runners with patellofemoral pain separately for males and females.

Risk factors for patellofemoral pain: a systematic review and meta-analysis.

BACKGROUND: Patellofemoral pain (PFP) is a prevalent condition commencing at various points throughout life. We aimed to provide an evidence synthesis concerning predictive variables for PFP, to aid development of preventative interventions. METHODS: We searched Medline, Web of Science and SCOPUS until February 2017 for prospective studies investigating at least one potential risk factor for future PFP. Two independent reviewers appraised methodological quality using the Newcastle-Ottawa Scale. We conducted meta-analysis where appropriate, with standardised mean differences (SMD) and risk ratios calculated for continuous and nominal scaled data. RESULTS: This review included 18 studies involving 4818 participants, of whom 483 developed PFP (heterogeneous incidence 10%). Three distinct subgroups (military recruits, adolescents and recreational runners) were identified. Strong to moderate evidence indicated that age, height, weight, body mass index (BMI), body fat and Q angle were not risk factors for future PFP. Moderate evidence indicated that quadriceps weakness was a risk factor for future PFP in the military, especially when normalised by BMI (SMD -0.69, CI -1.02, -0.35). Moderate evidence indicated that hip weakness was not a risk factor for future PFP (multiple pooled SMDs, range -0.09 to -0.20), but in adolescents, moderate evidence indicated that increased hip abduction strength was a risk factor for future PFP (SMD 0.71, CI 0.39, 1.04). CONCLUSIONS: This review identified multiple variables that did not predict future PFP, but quadriceps weakness in military recruits and higher hip strength in adolescents were risk factors for PFP. Identifying modifiable risk factors is an urgent priority to improve prevention and treatment outcomes.

The effects & mechanisms of increasing running step rate: A feasibility study in a mixed-sex group of runners with patellofemoral pain.

OBJECTIVES: To explore feasibility of recruitment and retention of runners with patellofemoral pain (PFP), before delivering a step rate intervention. DESIGN: Feasibility study. SETTING: Human performance laboratory. PARTICIPANTS: A mixed-sex sample of runners with PFP (n = 11). MAIN OUTCOME MEASURES: Average/worst pain and the Kujala Scale were recorded pre/post intervention, alongside lower limb kinematics and surface electromyography (sEMG), sampled during a 3 KM treadmill run. RESULTS: Recruitment and retention of a mixed-sex cohort was successful, losing one participant to public healthcare and with kinematic and sEMG data lost from single participants only. Clinically meaningful reductions in average (MD = 2.1, d = 1.7) and worst pain (MD = 3.9, d = 2.0) were observed. Reductions in both peak knee flexion (MD = 3.7°, d = 0.78) and peak hip internal rotation (MD = 5.1°, d = 0.96) were observed, which may provide some mechanistic explanation for the identified effects. An increase in both mean amplitude (d = 0.53) and integral (d = 0.58) were observed for the Vastus Medialis Obliqus (VMO) muscle only, of questionable clinical relevance. CONCLUSIONS: Recruitment and retention of a mixed sex PFP cohort to a step rate intervention involving detailed biomechanical measures is feasible. There are indications of both likely efficacy and associated mechanisms. Future studies comparing the efficacy of different running retraining approaches are warranted.

Runners with patellofemoral pain have altered biomechanics which targeted interventions can modify: A systematic review and meta-analysis.

Patellofemoral pain (PFP) is the most prevalent running pathology and associated with multi-level biomechanical factors. This systematic review aims to guide treatment and prevention of PFP by synthesising prospective, observational and intervention studies that measure clinical and biomechanical outcomes in symptomatic running populations. Medline, Web of Science and CINAHL were searched from inception to April 2015 for prospective, case-control or intervention studies in running-related PFP cohorts. Study methodological quality was scored by two independent raters using the modified Downs and Black or PEDro scales, with meta-analysis performed where appropriate. 28 studies were included. Very limited evidence indicates that increased peak hip adduction is a risk factor for PFP in female runners, supported by moderate evidence of a relationship between PFP and increased peak hip adduction, internal rotation and contralateral pelvic drop, as well as reduced peak hip flexion. Limited evidence was also identified that altered peak force and time to peak at foot level is a risk factor for PFP development. Limited evidence from intervention studies indicates that both running retraining and proximal strengthening exercise lead to favourable outcomes in both pain and function, but only running retraining significantly reduces peak hip adduction, suggesting a possible kinematic mechanism. Put together, these findings highlight limited but coherent evidence of altered biomechanics which interventions can alter with resultant symptom change in females with PFP. There is a clear need for high quality prospective studies of intervention efficacy with measurement of explanatory mechanisms.

Dynamic foot function as a risk factor for lower limb overuse injury: a systematic review.

BACKGROUND: Dynamic foot function is considered a risk factor for lower limb overuse injuries including Achilles tendinopathy, shin pain, patellofemoral pain and stress fractures. However, no single source has systematically appraised and summarised the literature to evaluate this proposed relationship. The aim of this systematic review was to investigate dynamic foot function as a risk factor for lower limb overuse injury. METHODS: A systematic search was performed using Medline, CINAHL, Embase and SportDiscus in April 2014 to identify prospective cohort studies that utilised dynamic methods of foot assessment. Included studies underwent methodological quality appraisal by two independent reviewers using an adapted version of the Epidemiological Appraisal Instrument (EAI). Effects were expressed as standardised mean differences (SMD) for continuous scaled data, and risk ratios (RR) for nominal scaled data. RESULTS: Twelve studies were included (total n = 3,773; EAI 0.44 to 1.20 out of 2.00, representing low to moderate quality). There was limited to very limited evidence for forefoot, midfoot and rearfoot plantar loading variables (SMD 0.47 to 0.85) and rearfoot kinematic variables (RR 2.67 to 3.43) as risk factors for patellofemoral pain; and plantar loading variables (forefoot, midfoot, rearfoot) as risk factors for Achilles tendinopathy (SMD 0.81 to 1.08). While there were significant findings from individual studies for plantar loading variables (SMD 0.3 to 0.84) and rearfoot kinematic variables (SMD 0.29 to 0.62) as risk factors for 'non-specific lower limb overuse injuries', these were often conflicting regarding different anatomical regions of the foot. Findings from three studies indicated no evidence that dynamic foot function is a risk factor for iliotibial band syndrome or lower limb stress fractures. CONCLUSION: This systematic review identified very limited evidence that dynamic foot function during walking and running is a risk factor for patellofemoral pain, Achilles tendinopathy, and non-specific lower limb overuse injuries. It is unclear whether these risk factors can be identified clinically (without sophisticated equipment), or modified to prevent or manage these injuries. Future prospective cohort studies should address methodological limitations, avoid grouping different lower limb overuse injuries, and explore clinically meaningful representations of dynamic foot function.

Foot posture as a risk factor for lower limb overuse injury: a systematic review and meta-analysis.

BACKGROUND: Static measures of foot posture are regularly used as part of a clinical examination to determine the need for foot level interventions. This is based on the premise that pronated and supinated foot postures may be risk factors for or associated with lower limb injury. This systematic review and meta-analysis investigates foot posture (measured statically) as a potential risk factor for lower limb overuse injuries. METHODS: A systematic search was performed using Medline, CINAHL, Embase, SportDiscus in April 2014, to identify prospective cohort studies that investigated foot posture and function as a risk factor for lower limb overuse injury. Eligible studies were classified based on the method of foot assessment: (i) static foot posture assessment; and/or (ii) dynamic foot function assessment. This review presents studies evaluating static foot posture. The methodological quality of included studies was evaluated by two independent reviewers, using an adapted version of the Epidemiological Appraisal Instrument (EAI). Where possible, effects were expressed as standardised mean differences (SMD) for continuous scaled data, and risk ratios (RR) for nominal scaled data. Meta-analysis was performed where injuries and outcomes were considered homogenous. RESULTS: Twenty-one studies were included (total n = 6,228; EAI 0.8 to 1.7 out of 2.0). There was strong evidence that a pronated foot posture was a risk factor for medial tibial stress syndrome (MTSS) development and very limited evidence that a pronated foot posture was a risk factor for patellofemoral pain development, although associated effect sizes were small (0.28 to 0.33). No relationship was identified between a pronated foot posture and any other evaluated pathology (i.e. foot/ankle injury, bone stress reactions and non-specific lower limb overuse injury). CONCLUSION: This systematic review identified strong and very limited evidence of small effect that a pronated foot posture is a risk factor for MTSS and patellofemoral pain respectively. Evaluation of static foot posture should be included in a multifactorial assessment for both MTSS and patellofemoral pain, although only as a part of the potential injury risk profile. Whilst the included measures are clinically applicable, further studies are required to determine their relationship with dynamic foot function.