Effects of Altering Trunk Position during Landings on Patellar Tendon Force and Pain

Concussion History Moderates Trunk Motion and Lower Extremity Biomechanical Relationships During Jump Landing and Cutting

Concussion history, trunk motion, and lower extremity biomechanics associate with musculoskeletal injury risk. We aimed to examine the interaction between concussion history and trunk motion as possible modifiable factors for injury risk biomechanics during jump landing and cutting. Division I female athletes (24 with, 20 without concussion history) performed jump landings and jump-to-cuts at 45° in the opposite direction of the landing limb. We used multiple linear regressions with interaction terms to examine ankle dorsiflexion angle, knee flexion and abduction angle, and external knee flexion and abduction moment. We observed a group by trunk flexion interaction for nondominant external knee flexion moment (P = .042) during jump landing. Concussion history associated with increased external knee flexion moment as trunk flexion increased. We observed a group by trunk flexion interaction for the dominant limb dorsiflexion angle (P = .044), and group by trunk lateral bending interactions for the dominant (P = .039) and nondominant limb (P = .016) external knee flexion moment during cutting. During cutting, concussion history associated with decreased dominant dorsiflexion angles as trunk flexion increased, and decreased dominant and nondominant external knee flexion moment as lateral bending toward the planted limb increased. Concussion history associated with atypical biomechanics as trunk flexion and lateral bending increased.

Association Between Longitudinal Changes in Patellar Tendon Abnormality and Land-Jump Biomechanics in Male Collegiate Basketball Players

Background

The relationship between self-reported symptoms and the severity of patellar tendon abnormality (PTA) as seen on magnetic resonance imaging and ultrasound is unclear, but biomechanical testing may resolve this.

Purpose

To (1) compare land-jump limb biomechanics between pre- and postseason timepoints, (2) assess whether seasonal changes in biomechanics are associated with seasonal changes in PTA and symptom severity, and (3) explore models that identify seasonal changes in PTA and symptoms with seasonal changes in biomechanics in collegiate basketball players.

Study Design

Cohort study; Level of evidence, 2.

Methods

Victorian Institute of Sport Assessment Scale - Patellar Tendon (VISA-P) scores and bilateral measurements from 18 National Collegiate Athletic Association Division I and II male basketball players (n = 36 limbs) at the preseason (visit 1) and postseason (visit 2) timepoints were collected. PTA was graded with ultrasound and magnetic resonance imaging morphology measurements proximally and distally, and 3-dimensional lower extremity sagittal kinematics and kinetics were measured during a land-jump test. Multivariate and chi-square analyses assessed timepoint differences. The association of seasonal (Δ = visit 2 - visit 1) biomechanics with seasonal morphology (ΔPTA: no change/worsened) and symptoms (ΔVISA-P: improved/no change/worsened) was tested with multivariate models. Logistic regressions modeled the accuracy of seasonal biomechanics to classify seasonal PTA and symptoms.

Results

Three athletes (6 limbs) at visit 1 and 2 athletes (4 limbs) at visit 2 were symptomatic. VISA-P scores were not significantly different between preseason and postseason. Regarding PTA, multivariate analyses found differences among grouped ground-reaction force variables (P < .05); univariate analyses found that worsened PTA was associated with seasonal decreases in peak vertical jumping force and with seasonal increases in knee flexion velocity at contact and maximum knee flexion velocity (P < .05 for all). Regarding VISA-P scores, multivariate analyses found differences among grouped hip (P < .01) and ankle (P < .05) kinematic variables; univariate analyses found that worsened VISA-P was associated with seasonal increases in hip (P < .01) and knee (P < .01) flexion velocity at contact and seasonal increases in ankle range of motion (P < .05).

Conclusion

The findings demonstrated an association between seasonal changes in dynamic lower extremity biomechanics and seasonal changes in patellar tendon imaging signals as well as self-reported symptoms.

Association Between Patellar Tendon Abnormality and Land-Jump Biomechanics in Male Collegiate Basketball Players During the Preseason

Background

Patellar tendinopathy is a degenerative condition that predominantly affects jumping athletes. Symptoms may be subtle or nonexistent at preseason, but structural abnormalities may be present. Assessing patellar tendon abnormality (PTA) through magnetic resonance imaging (MRI) and ultrasound (US) and classifying symptoms using the Victorian Institute for Sport Assessment-Patellar tendon (VISA-P) may provide useful insights if combined with biomechanics measurements.

Purpose

To (1) assess whether land-jump biomechanical patterns are associated with clinically pertinent PTA as seen on imaging and through VISA-P scores and (2) model the contributing risk and accuracy of biomechanics to classify PTA and symptomatic observations.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 26 National Collegiate Athletic Association Division I and II male basketball players (n = 52 limbs) were recruited during the preseason. We collected VISA-P scores, bilateral PTA through US and MRI morphology measurements, and bilateral 3-dimensional lower extremity kinematics and kinetics measurements from a land-jump test from an 18-inch-high (45.7-cm-high) box. Statistically, each limb was treated independently. The association of biomechanics with PTA and symptoms (VISA-P score <80) was tested with multivariate models and post hoc tests. Logistic regression modeled relative risk and accuracy of biomechanical variables to classify PTA and symptomatic limbs.

Results

There were 19 to 24 limbs with PTA depending on US and MRI measurements. Differences in hip and knee kinematic strategies and ground-reaction loads were associated with PTA and symptomatic limbs. Peak landing vertical ground-reaction force was significantly decreased (169 ± 26 vs 195 ± 29 %body weight; P = .001), and maximum hip flexion velocity was significantly increased (416 ± 74 vs 343 ± 94 deg/s; P = .005) in limbs with versus without PTA on imaging. Knee flexion at the initial contact was decreased in symptomatic versus healthy limbs (17°± 5° vs 21°± 5°, respectively; P = .045). Regression models classified PTA limbs and symptomatic limbs with 71.2% to 86.5% accuracy. Hip and knee maximum flexion velocity and vertical ground-reaction force variables were most common across models observing clinically pertinent PTA.

Conclusion

Our findings suggested that functional kinematic and kinetic biomechanical strategies at the hip and knee were associated with PTA, identified on imaging, and symptomatic limbs.

Patellar Tendon Load Progression during Rehabilitation Exercises: Implications for the Treatment of Patellar Tendon Injuries

PURPOSE

This study aimed to evaluate patellar tendon loading profiles (loading index, based on loading peak, loading impulse, and loading rate) of rehabilitation exercises to develop clinical guidelines to incrementally increase the rate and magnitude of patellar tendon loading during rehabilitation.

METHODS

Twenty healthy adults (10 females/10 males, 25.9 ± 5.7 yr) performed 35 rehabilitation exercises, including different variations of squats, lunge, jumps, hops, landings, running, and sports specific tasks. Kinematic and kinetic data were collected, and a patellar tendon loading index was determined for each exercise using a weighted sum of loading peak, loading rate, and cumulative loading impulse. Then the exercises were ranked, according to the loading index, into tier 1 (loading index ≤0.33), tier 2 (0.33 < loading index <0.66), and tier 3 (loading index ≥0.66).

RESULTS

The single-leg decline squat showed the highest loading index (0.747). Other tier 3 exercises included single-leg forward hop (0.666), single-leg countermovement jump (0.711), and running cut (0.725). The Spanish squat was categorized as a tier 2 exercise (0.563), as was running (0.612), double-leg countermovement jump (0.610), single-leg drop vertical jump (0.599), single-leg full squat (0.580), double-leg drop vertical jump (0.563), lunge (0.471), double-leg full squat (0.428), single-leg 60° squat (0.411), and Bulgarian squat (0.406). Tier 1 exercises included 20 cm step up (0.187), 20 cm step down (0.288), 30 cm step up (0.321), and double-leg 60° squat (0.224).

CONCLUSIONS

Three patellar tendon loading tiers were established based on a combination of loading peak, loading impulse, and loading rate. Clinicians may use these loading tiers as a guide to progressively increase patellar tendon loading during the rehabilitation of patients with patellar tendon disorders and after anterior cruciate ligament reconstruction using the bone-patellar tendon-bone graft.

Hip and knee kinematics, center of pressure position, and ground reaction force are associated with Achilles tendon force during jump landing

PURPOSE

Jump-landing exercises are often performed during the rehabilitation of Achilles tendon (AT) injuries. However, the factors that affect the AT force (ATF) during landing are unclear. This study aimed to determine the kinematics and ground reaction force (GRF) variables associated with the peak ATF during a drop vertical jump (DVJ).

METHODS

The landing phase of DVJ was evaluated in 101 healthy participants (46 males, age: 21.2 ± 1.4 years old) using a three-dimensional motion analysis system with two force plates. ATF was estimated from the ankle flexion angle and moment. Univariate and multivariate regression analyses were performed with the peak ATF as the dependent variable. The vertical GRF (VGRF), center of pressure (COP), forward trunk leaning, hip/knee/ankle joint angles at peak ATF, and sex were used as independent variables.

RESULTS

In the univariate regression analysis, larger VGRF (β = 0.813), more anterior COP position (β = 0.214), smaller knee flexion (β = -0.251) and adduction (β = -0.252), smaller hip flexion (β = -0.407), smaller forward trunk lean (β = -0.492), and male sex (β = -0.282) were significantly associated with a larger peak ATF. Multivariate analysis revealed that larger VGRF (β = 1.018), more anterior COP position (β = 0.320), a larger knee (β = 0.442), and smaller hip flexion (β = -0.205) were associated with the larger peak ATF.

CONCLUSIONS

The VGRF, COP position, and knee and hip flexion were independently associated with ATF. Modifying these factors may be useful in managing tendon loading during jump-landing exercises.

Effect of movement-evoked and tonic experimental pain on muscle force production

INTRODUCTION

When performing an exercise or a functional test, pain that is evoked by movement or muscle contraction could be a stronger stimulus for changing how individuals move compared to tonic pain. We investigated whether the decrease in muscle force production is larger when experimentally-induced knee pain is directly associated to the torque produced (movement-evoked) compared to a constant painful stimulation (tonic).

METHODS

Twenty-one participants performed three isometric knee extension maximal voluntary contractions without pain (baseline), during pain, and after pain. Knee pain was induced using sinusoidal electrical stimuli at 10 Hz over the infrapatellar fat pad, applied continuously or modulated proportionally to the knee extension torque. Peak torque and contraction duration were averaged across repetitions and normalized to baseline.

RESULTS

During tonic pain, participants reported lower pain intensity during the contraction than at rest (p < 0.001), whereas pain intensity increased with contraction during movement-evoked pain (p < 0.001). Knee extension torque decreased during both pain conditions (p < 0.001), but a larger reduction was observed during movement-evoked compared to tonic pain (p < 0.001). Participants produced torque for longer during tonic compared to movement-evoked pain (p = 0.005).

CONCLUSION

Our results indicate that movement-evoked pain was a more potent stimulus to reduce knee extension torque than tonic pain. The longer contraction time observed during tonic pain may be a result of a lower perceived pain intensity during muscle contraction. Overall, our results suggest different motor adaptation to tonic and movement-evoked pain and support the notion that motor adaptation to pain is a purposeful strategy to limit pain. This mechanistic evidence suggests that individuals experiencing prevalently tonic or movement-evoked pain may exhibit different motor adaptations, which may be important for exercise prescription.

The effect of fatigue on spike jump biomechanics in view of patellar tendon loading in volleyball

BACKGROUND AND OBJECTIVE

Patellar tendinopathy (PT) is a highly prevalent overuse injury in volleyball and is often linked with overloading of the patellar tendon. Little is known, however, about whether and how patellar tendon loading is affected by fatigue during the most challenging jump activity in volleyball. Therefore, this study investigates the effect of a high-intensity, intermittent fatigue protocol on movement alterations in terms of patellar tendon loading during a volleyball spike jump.

METHODS

Forty-three male volleyball players participated in this study. Three-dimensional full-body kinematics and kinetics were collected when performing a spike jump before and after the fatigue protocol. Sagittal plane joint angles, joint work and patellar tendon loading were calculated and analyzed with curve analyses using paired sample t-tests to investigate fatigue effects (p < 0.05).

RESULTS

Fatigue induced a stiffer lower extremity landing strategy together with prolonged pelvis-trunk flexion compared to baseline (p = 0.001-0.005). Decreased patellar tendon forces (p = 0.001-0.010) and less eccentric knee joint work (-5%, p < 0.001) were observed after the fatigue protocol compared to baseline.

CONCLUSION

Protective strategies seem to be utilized in a fatigued state to avoid additional tensile forces acting on the patellar tendon, including proximal compensations and stiff lower extremity landings. We hypothesize that players might be more prone for developing PT if eccentric patellar tendon loads are high in the non-fatigued state and/or these loads are somehow not decreased after fatigue.

The effect of trunk and shank position on the hip-to-knee moment ratio in a bilateral squat

OBJECTIVES

The effect of knee position on joint moments during squats has been studied; however, the effect of trunk angle has been less well investigated. This study evaluated the effect of both trunk and knee sagittal plane position on the distribution of moments between the hip and knee extensors during the bilateral squat.

DESIGN

Observational study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

One hundred individuals performed bilateral squats.

MAIN OUTCOME MEASURES

Motion and force data were collected using motion capture and force plates. Trunk and shank angles and hip and knee moments were calculated. A linear regression was used to associate the ratio between the hip and knee moments (hip-to-knee moment ratio) with the sagittal plane trunk and shank angles, while accounting for six squat depths (between 60° and 110° of knee flexion) and side.

RESULTS

Trunk angle and shank angle each contributed to the hip-to-knee moment ratio (P < .001) with trunk accounting for a higher proportion of variance than the other variables. The hip-to-knee moment ratio increased with increasing trunk angle and with decreasing shank angle.

CONCLUSIONS

This large cohort study supports the use of trunk position to instruct squat technique with the goal of modifying hip and knee moments.

The Effects of Increasing Trunk Flexion During Stair Ascent on the Rate and Magnitude of Achilles Tendon Force in Asymptomatic Females

Research indicates that increasing trunk flexion may optimize patellofemoral joint loading. However, this postural change could cause an excessive Achilles tendon force (ATF) and injury risk during movement. This study aimed to examine the effects of increasing trunk flexion during stair ascent on ATF, ankle biomechanics, and vertical ground reaction force in females. Twenty asymptomatic females (age: 23.4 [2.5] y; height: 1.6 [0.8] m; mass: 63.0 [12.2] kg) ascended stairs using their self-selected and flexed trunk postures. Compared with the self-selected trunk condition, decreases were observed for peak ATF (mean differences [MD] = 0.14 N/kg; 95% confidence interval [CI], 0.06 to 0.23; Cohen d = -1.2; P = .003), average rate of ATF development (MD = 0.25 N/kg/s; 95% CI, 0.07 to 0.43; Cohen d = -0.9; P = .010), ankle plantar flexion moment (MD = 0.08 N·m/kg; 95% CI, 0.03 to 0.13; Cohen d = -1.1; P = .005), and vertical ground reaction force (MD = 38.6 N/kg; 95% CI, 20.3 to 56.90; Cohen d = -1.8; P < .001). Increasing trunk flexion did not increase ATF. Instead, this postural change was associated with a decreased ATF rate and magnitude and may benefit individuals with painful Achilles tendinopathy.

The Effect of Fatigue on Trunk and Pelvic Jump-Landing Biomechanics in View of Lower Extremity Loading: A Systematic Review

Fatigue has often been considered a risk factor for developing sports injuries, modulating lower extremity jump-landing biomechanics. The impact of fatigue on proximal trunk and pelvic biomechanics has been suggested to play an important role in lower extremity loading and injury risk, yet the available evidence remains ambiguous as the trunk and pelvis were often not the primary focus of research. Therefore, the purpose of this systematic review was to determine how fatigue affects trunk and pelvic three-dimensional jump-landing biomechanics. PubMed (MEDLINE), Web of Science, Embase, CINAHL and SPORTDiscus were consulted up to and including April 2022 for potential studies investigating the effect of fatigue on trunk and pelvic kinematics, kinetics and/or muscular activity during jump-landing tasks in healthy, physically active populations. Methodological quality of the studies was assessed by the modified Downs and Black checklist. Twenty-one studies were included and methodological quality was moderate to high among these studies. The results indicate prevailing evidence for more trunk flexion during standardized jump-landing tasks after lower extremity muscle fatigue. Otherwise, lumbo-pelvic-hip muscle fatigue does not seem to elicit major detrimental changes to these jump-landing biomechanics. Although a wide variability of trunk and pelvic jump-landing strategies was observed, the results provide evidence for increased trunk flexion after lower extremity muscle fatigue. This proximal strategy is suggested to help unload fatigued lower extremity structures and lack of this compensation might increase knee injury risk.

Trunk Biomechanics in Individuals with Knee Disorders: A Systematic Review with Evidence Gap Map and Meta-analysis

BACKGROUND

The trunk is the foundation for transfer and dissipation of forces throughout the lower extremity kinetic chain. Individuals with knee disorders may employ trunk biomechanical adaptations to accommodate forces at the knee or compensate for muscle weakness. This systematic review aimed to synthesize the literature comparing trunk biomechanics between individuals with knee disorders and injury-free controls.

METHODS

Five databases were searched from inception to January 2022. Observational studies comparing trunk kinematics or kinetics during weight-bearing tasks (e.g., stair negotiation, walking, running, landings) between individuals with knee disorders and controls were included. Meta-analyses for each knee disorder were performed. Outcome-level certainty was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE), and evidence gap maps were created.

RESULTS

A total of 81 studies investigating trunk biomechanics across six different knee disorders were included (i.e., knee osteoarthritis [OA], total knee arthroplasty [TKA], patellofemoral pain [PFP], patellar tendinopathy [PT], anterior cruciate ligament deficiency [ACLD], and anterior cruciate ligament reconstruction [ACLR]). Individuals with knee OA presented greater trunk flexion during squatting (SMD 0.88, 95% CI 0.58-1.18) and stepping tasks (SMD 0.56, 95% CI 0.13-.99); ipsilateral and contralateral trunk lean during walking (SMD 1.36; 95% CI 0.60-2.11) and sit-to-stand (SMD 1.49; 95% CI 0.90-2.08), respectively. Greater trunk flexion during landing tasks in individuals with PFP (SMD 0.56; 95% CI 0.01-1.12) or ACLR (SMD 0.48; 95% CI 0.21-.75) and greater ipsilateral trunk lean during single-leg squat in individuals with PFP (SMD 1.01; 95% CI 0.33-1.70) were also identified. No alterations in trunk kinematics of individuals with TKA were identified. Evidence gap maps outlined the lack of investigations for individuals with PT or ACLD, as well as for trunk kinetics across knee disorders.

CONCLUSION

Individuals with knee OA, PFP, or ACLR present with altered trunk kinematics in the sagittal and frontal planes. The findings of this review support the assessment of trunk biomechanics in these individuals in order to identify possible targets for rehabilitation and avoidance strategies.

TRIAL REGISTRATION

PROSPERO registration number: CRD42019129257.

Knee Movement Characteristics of Basketball Players in Landing Tasks Before Onset of Patellar Tendinopathy: A Prospective Study

Background

Patellar tendinopathy is one of the most common injuries for basketball players. Jumping and landing movement patterns are potential risk factors for patellar tendinopathy.

Hypothesis

Male college basketball players who developed patellar tendinopathy would demonstrate greater peak vertical ground reaction force and knee flexion angular velocity, and smaller knee flexion range of motion and knee flexion angles at initial contact compared to players who did not develop the injury when performing a stop-jump task within a year prior to the onset of the injury.

Study Design

Prospective study.

Methods

Freshmen college basketball male players (n = 181) were recruited for three consecutive years and followed to the end of the third year of the study. Three-dimensional kinematic and kinetic data during a stop-jump task were collected for all participants at the beginning of each school year. Peak vertical ground reaction force, knee flexion angle at initial foot contact with the ground, range of motion for knee flexion and maximal knee flexion angular velocity during the landing phases of the stop-jump task were collected and calculated. Development of patellar tendinopathy was monitored in follow-up. Independent t-tests and Cohen's d effect sizes (ES) were used to compare movement patterns between injury and no injury groups for each school year.

Results

A total of 60 knees developed patellar tendinopathy. The injury groups had a significantly greater peak vertical ground reaction force in freshmen and junior years (P = 0.020, ES = 0.13; P = 0.046, ES = 0.17), smaller knee flexion ROM in freshmen year (P = 0.002, ES = 0.10), and greater maximum knee flexion angular velocity in freshmen and junior year (P = 0.012, ES = 0.10; P = 0.001, ES = 0.35) during the horizontal landing phase before the takeoff of the jump compared to the no injury groups. The injury groups also had a significantly smaller knee flexion angle at initial contact during vertical landing phase after the takeoff of the jump in freshmen and junior years (P = 0.001, ES = 0.36; P = 0.001; ES = 0.37) during vertical landing phase.

Conclusion

Peak vertical ground reaction force, knee flexion angle at initial foot contact, knee flexion range of motion, and maximum knee flexion angular velocity are associated with patellar tendinopathy among male college basketball players in different school years.

Association of Ankle Dorsiflexion and Landing Forces in Jumping Athletes

BACKGROUND

Dorsiflexion range of motion restriction has been associated with patellar tendinopathy, but the mechanisms of how dorsiflexion restriction could contribute to knee overload remain unknown.

HYPOTHESIS

Peak ankle dorsiflexion and ankle dorsiflexion excursion are negatively associated with peak vertical ground-reaction force (vGRF) and loading rate, and with peak patellar tendon force and loading rate, and positively associated with peak ankle plantar flexor moment.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 4.

METHODS

Kinematic and kinetic data of 26 healthy recreational jumping athletes were measured during a single-leg drop vertical jump. Pearson's correlation coefficients were calculated to establish the association between peak ankle dorsiflexion and ankle dorsiflexion excursion with peak vGRF and vGRF loading rate, with peak patellar tendon force and patellar tendon force loading rate, and with peak ankle plantar flexor moment.

RESULTS

Ankle dorsiflexion excursion negatively correlated with peak vGRF loading rate (r = -0.49; P = 0.011) and positively correlated with peak ankle flexor plantar moment (r = 0.52; P = 0.006). In addition, there was a positive correlation between peak ankle dorsiflexion and peak vGRF (r = 0.39; P = 0.05).

CONCLUSION

Ankle kinematics are associated with vGRF loading rate, ankle flexor plantar moment and peak vGRF influencing knee loads, but no association was observed between ankle kinematics and patellar tendon loads.

CLINICAL RELEVANCE

These results suggest that increasing ankle dorsiflexion excursion may be an important strategy to reduce lower limb loads during landings but should not be viewed as the main factor for reducing patellar tendon force.

Preventive effect of tailored exercises on patellar tendinopathy in elite youth athletes: A cohort study

OBJECTIVE

To investigate the effects of an intervention with tailored exercises on the incidence of patellar tendinopathy (PT) in elite youth jumping athletes.

DESIGN

Prospective crossover cohort.

SETTING

One sport club facility.

PARTICIPANTS

271 elite youth basketball and volleyball player were followed in the first year of the study (Observation year) and 270 athletes were followed in the second year (intervention year).

MAIN OUTCOME MEASURE

Incidence rates of PT per 1,000h of exposure. Cox survival analysis was used to verify the effects of the intervention (exercises implemented according to the findings of a preseason assessment) on PT incidence.

RESULTS

The exercise prevention program significantly reduced the number of cases of PT, with athletes submitted to the intervention showing 51% less risk of developing PT. The overall PT incidence in the Observation year (5.9 per 1,000h of exposure) was significantly higher than that in the intervention year (2.8 per 1,000h of exposure) (P = .037). Twenty-six athletes developed PT in the observation year, whereas 13 athletes developed PT in the intervention year.

CONCLUSIONS

A tailored preventive program may be able to reduce the incidence of patellar tendinopathy, especially in male youth volleyball athletes. Randomized controlled trials are encouraged to confirm these findings.

Immediate Improvements in Patellofemoral Pain Are Associated With Sagittal Plane Movement Training to Improve Use of Gluteus Maximus Muscle During Single Limb Landing

OBJECTIVE

The authors sought to examine the immediate effects of movement training aimed at improving use of gluteus maximus (GMAX) in the sagittal plane on hip internal rotation and self-reported patellofemoral pain (PFP) during single-limb landing.

METHODS

Seventeen females with PFP participated. Lower extremity kinematics and kinetics, GMAX activation, and self-reported PFP were obtained before and after a single-session movement training program aimed at increasing the use of GMAX. Dependent variables of interest included self-reported PFP, average GMAX activation, average hip extensor moment, and peak hip internal rotation. Post-training changes were evaluated using paired t tests and Wilcoxon signed rank tests.

RESULTS

Following movement training, self-reported PFP decreased significantly (mean [standard deviation]) (3.9 [1.1] vs 0.8 [1.3] on a 0-10 scale). Additionally, significant increases were observed for the average hip extensor moment (0.6 [0.3] vs 1.8 [0.4] Nm/kg) and average GMAX activation (41.0% [18.3] vs 51.6% [25.7] maximum voluntary isometric contraction), whereas peak hip internal rotation decreased significantly (8.5 degrees [5.8] vs 6.0 degrees [5.3]).

CONCLUSION

Movement training aimed at improving the use of GMAX in the sagittal plane resulted in clinically relevant changes in self-reported pain, GMAX activation, and hip kinetics and kinematics. Improving the use of GMAX during movement merits consideration when designing rehabilitation programs for females with PFP.

IMPACT

The current study highlights the clinical utility of movement training for persons with PFP and provides a biomechanical rationale for its use as a potential intervention in this population.

Are Landing Patterns in Jumping Athletes Associated with Patellar Tendinopathy? A Systematic Review with Evidence Gap Map and Meta-analysis

Background

Patellar tendinopathy (PT) is common and debilitating for jumping athletes. Intriguingly, despite its high prevalence and many research studies, a causal explanation for PT presence remains elusive.

Objective

Our objective was to investigate whether landing biomechanics among jumping athletes are associated with PT and can predict onset.

Methods

We conducted a systematic review with evidence gap map and meta-analysis. We searched three databases from inception to May 2021 for observational studies or trials evaluating landing biomechanics in jumping athletes with PT (JPTs). We assessed quality with a modified Downs and Black checklist, risk of bias with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool, and evidence levels with van Tulder’s criteria and provided an evidence gap map.

Results

One prospective cohort (moderate quality), one cross-sectional cohort (moderate quality), and 14 case–control (four high-, seven moderate-, and three low-quality) studies, including 104 JPTs, 14 with previous PT, 45 with asymptomatic patellar tendon abnormality (PTA), and 190 controls were retained. All studies had a high risk of bias. Meta-analysis showed an association between lower ankle dorsiflexion and the presence of tendinopathy during drop and spike landings, and JPTs had reduced knee joint power and work during volleyball approach or drop landings (moderate evidence). Limited evidence suggested that JPTs had lower patellar tendon loads during drop landings. Strong or moderate evidence showed no relation between PT and sagittal plane peak knee and hip angles or range of motion; hip, knee, or ankle angles at initial contact (IC); knee angular velocities, peak trunk kinematics, or trunk angles at IC; sagittal plane hip, knee, or ankle moments; and peak vertical ground reaction force (vGRF) and vGRF impulse. Identified gaps were that no study simultaneously investigated athletes with previous PT, current PT, and PTA, and studies of joint angular velocities at IC, ankle and hip angular velocities after touchdown, leg stiffness, loading rate of forces, and muscle activation are lacking.

Conclusion

Despite the voluminous literature, large number of participants, multitude of investigated parameters, and consistent research focus on landing biomechanics, only a few associations can be identified, such as reduced ankle dorsiflexion–plantarflexion range. Further, the quality of the existing literature is inadequate to draw strong conclusions, with only four high-quality papers being found. We were unable to determine biomechanical factors that predicted PT onset, as longitudinal/prospective studies enabling causal inference are absent. The identified gaps indicate useful areas in which to explore causal relationships to inform intervention development. Therefore, high-quality prospective studies are essential to definitively determine whether landing biomechanics play a part in the development, recurrence, or management of PT and represent a potential therapeutic or preventive target alongside non-biomechanical factors.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-021-01550-6.

Exploring the Justifications for Selecting a Drop Landing Task to Assess Injury Biomechanics: A Narrative Review and Analysis of Landings Performed by Female Netball Players

When assessing biomechanics in a laboratory setting, task selection is critical to the production of accurate and meaningful data. The injury biomechanics of landing is commonly investigated in a laboratory setting using a drop landing task. However, why this task is so frequently chosen is unclear. Therefore, this narrative review aimed to (1) identify the justification/s provided within the published literature as to why a drop landing task was selected to investigate the injury biomechanics of landing in sport and (2) use current research evidence, supplemented by a new set of biomechanical data, to evaluate whether the justifications are supported. To achieve this, a comprehensive literature search using Scopus, PubMed, and SPORTDiscus online databases was conducted for studies that had collected biomechanical data relating to sport injuries using a drop landing task. In addition, kinematic and kinetic data were collected from female netball players during drop landings and maximum-effort countermovement jumps from the ground to grab a suspended ball. The literature search returned a total of 149 articles that were reviewed to determine the justification for selecting a drop landing task. Of these, 54% provided no explicit justification to explain why a drop landing task was chosen, and 15% stated it was selected because it had been used in previous research. Other reasons included that the drop landing provides high experimental control (16%), is a functional sports task (11%), and is a dynamic task (6%). Evidence in the literature suggests that the biomechanical data produced with drop landings may not be as externally valid as more sport-specific tasks. Biomechanical data showed that the drop landing may not control center of mass fall height any better than maximum-effort countermovement jumps from the ground. Further, the frequently used step-off technique to initiate drop landings resulted in kinematic and kinetic asymmetries between lower limbs, which would otherwise be symmetrical when performing a countermovement jump from the ground. Researchers should consider the limitations of a drop landing task and endeavor to improve the laboratory tasks used to collect biomechanical data to examine the injury biomechanics of landing.

How strong is the evidence that conservative treatment reduces pain and improves function in individuals with patellar tendinopathy? A systematic review of randomised controlled trials including GRADE recommendations

OBJECTIVE

To determine the effectiveness of conservative treatment (CT) on pain and function in patients with patellar tendinopathy (PT) compared with minimal intervention (MI) or other invasive intervention, or in addition to decline eccentric squat.

METHODS

Searches were performed in MEDLINE, Embase, Cochrane, PEDro, SPORTDiscus, CINAHL and AMED databases. All randomised trials that evaluated CT (any intervention not involving invasive procedures or medication) in individuals with PT were included. Two reviewers screened studies, extracted data and assessed risk of bias of all included studies. Where suitable, meta-analyses were conducted; we assessed certainty of the evidence using GRADE methodology.

RESULTS

When compared with MI, CT did not improve pain (weighted mean difference (WMD) -2.6, 95% CI -6.5 to 1.2) or function (WMD 1.8, 95% CI -2.4 to 6.1) in the short-term (up to 3 months) follow-up. When compared with invasive intervention, CT did not improve pain (WMD 0.7, 95% CI -0.1 to 1.4) or function (WMD -6.6, 95% CI -13.3 to 0.2) in the short-term follow-up. No overall effects were found for combined CT (when a conservative intervention was added to decline eccentric squat) on pain (WMD -0.5, 95% CI -1.4 to 0.4) or function (WMD -2.3, 95 % -9.1 to 4.6) at short-term follow-up. Single studies showed an effect on pain with iontophoresis at short-term follow-up (d = 2.42) or dry needling at medium/long-term follow-up (d = 1.17) and function with exercise intervention at medium/long-term follow-up (over 3 months) (d = 0.83).

SUMMARY/CONCLUSION

Our estimates of treatment effect have only low to very low certainty evidence to support them. This field of sports medicine/sports physiotherapy urgently needs larger, high-quality studies with pain and function among the potential primary outcomes.

Promoting effective tendon healing and remodeling

Daily activities subject our tendons to accumulation of sub-rupture fatigue injury which can lead to tendon rupture. Consequently, tendinopathies account for over 30% of musculoskeletal consultations. We adopted a multidisciplinary approach to determine the role of the extracellular matrix (ECM) in the pathogenesis of tendinopathy and impaired healing of ruptured tendons. We have been investigating three main areas: (i) the pathogenesis of tendon degeneration; (ii) approaches to promoting remodeling of sub-rupture fatigue injuries; and the (iii) role of the ECM in promoting scarless tendon healing. In this Kappa Delta Young Investigator award paper, we describe the key discoveries made in each of our three research areas of focus. Briefly, we discovered that sub-rupture fatigue damage can accumulate from just one bout of fatigue loading. Furthermore, any attempt to repair the fatigue damage diminishes as the severity of induced damage increases. We have utilized exercise to develop animal models of exercise-led degeneration and exercise-led repair of sub-rupture fatigue damage injuries, wherein underlying mechanisms can be uncovered, thereby overcoming a major hurdle to development of therapeutics. Since damage accumulation ultimately leads to rupture that is characterized by formation of a mechanically inferior scar, we have used the MRL/MpJ mouse to evaluate the role of the systemic environment and the local tendon environment in driving regeneration to identify new therapeutic pathways to promote scarless healing. Our data suggests that the therapeutic potential of the MRL/MpJ provisional ECM should be further explored as it may harness biological and structural mechanisms to promote scarless healing. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3115-3124, 2018.

Isometric strength of the hip abductors and external rotators in athletes with and without patellar tendinopathy

PURPOSE

This study aims to compare the isometric strength of hip abductors and external rotators in male athletes with and without patellar tendinopathy (PT), and to examine the correlation between hip strength, pain, and functional scores.

METHODS

Sixty male athletes (30 with PT and 30 controls) were recruited from local volleyball and basketball teams. The isometric strength of the hip abductors and external rotators was quantified using a belt-stabilized handheld dynamometer. This study used the visual analog scale (VAS) and the Victorian Institute of Sport Assessment-Patella (VISA-p) questionnaire to measure the intensity of pain and functional scores in athletes with PT, respectively.

RESULTS

The normalized isometric strength of the hip abductors and external rotators was significantly less in the PT group compared with controls. In subjects with PT, the normalized isometric strength was decreased by 22.0% (p = 0.000) in the hip abductors and by 20.0% in the hip external rotators (p = 0.004), compared with controls. Significant correlations were found between the normalized isometric strength of the hip abductors and intensity of pain (r = - 0.70; p < 0.05) and VISA-p score (r = 0.63; p < 0.05) in the affected leg in athletes with unilateral PT.

CONCLUSIONS

Athletes with PT have decreased isometric strength in their hip abductors and external rotators when compared with controls. In subjects with unilateral PT, decreased isometric strength in the hip abductors is associated with greater intensity of pain and lower functional scores. Results of this study implied that hip muscle assessment and strengthening should be included for reconditioning and rehabilitation in athletes with PT.