Relationships between tendon structure and clinical impairments in patients with patellar tendinopathy

Do physical or imaging changes explain the effectiveness of progressive tendon loading exercises? A causal mediation analysis of athletes with patellar tendinopathy

OBJECTIVES

To investigate whether the effectiveness of progressive tendon loading exercises (PTLE) on patellar tendinopathy is mediated through changes in physical or imaging properties.

DESIGN

Mediation analyses based on a randomized clinical trial (n = 76) in patellar tendinopathy comparing PTLE with eccentric exercise therapy (EET).

METHODS

Pain-related disability on Victorian Institute of Sports Assessment-Patella (VISA-P, 0 to 100) and pain (Visual Analogue Score) after single-leg decline squat (VAS-SLDS, 0 to 10) at 24 weeks were outcome measures. Selected mediators, including the physical (quadriceps muscle strength, ankle dorsiflexion range, jumping performance) and imaging domains (ultrasonographic tendon thickness and degree of neovascularization), were measured at 12 weeks. Directed acyclic graphs were performed to identify critical confounders. Causal mediation analysis was used to estimate natural indirect, natural direct and total effects by a simulation approach under the counterfactual framework.

RESULTS

Complete data from 61 of 76 participants were included. There was no evidence showing that the beneficial effect of PTLE on VISA-P or VAS-SLDS outcomes was mediated by changes in any of the selected physical or imaging variables. The indirect effects for all mediators were unsubstantial (estimates ranging from -1.63 to 1.53 on VISA-P and -0.20 to 0.19 on VAS-SLDS), with all 95 % confidence intervals containing zero.

CONCLUSIONS

The beneficial effect of PTLE on patellar tendinopathy was not mediated by changes in physical properties, tendon thickness or degree of neovascularization. Healthcare professionals may consider exploring other potential factors when managing patients with patellar tendinopathy, but further large-scale research is needed to confirm these results and to identify alternative treatment targets.

Is Achilles tendon structure associated with functional ability and chronic ankle instability in military recruits?

OBJECTIVE

To determine the relationship between Achilles tendon (AT) structure, functional ability and chronic ankle instability (CAI) in military recruits.

METHODS

Three hundred and sixty newly recruited infantry male soldiers recruited in April 2022 were assessed for AT structure by Ultrasound Tissue Characterization (UTC), for functional abilities (included proprioception ability, heel-raise test, dynamic postural balance, and hopping agility ability) and for CAI (recurrent sprains and a positive perceived instability).

RESULTS

Soldiers that were identified with disorganized tendon had significantly lower heel-raise and agility scores compared to those with organized tendon structures (33.6 ± 18.1(n) vs. 49.9 ± 28.9(n), p < 0.001; and 5.39 ± 2.12(n) vs. 6.16 ± 1.90(n), p = 0.002, respectively). The best discriminator between soldiers with organized vs. disorganized structure, was heel-raise test (AUC = 0.741). Moreover, soldiers with disorganized AT structure had a higher prevalence of CAI compared with those with organized tendon structures (p < 0.05).

CONCLUSION

Recruits with disorganized tendon structures displayed reduced heel-raise score, agility ability and dynamic postural-balance and greater ankle instability. Inferior tendon quality at the onset of military service is an important physical indicator to consider when seeking to manage future injuries and potential for physical performance. Pre-recruitment screening of the AT structure, CAI, and functional abilities, especially in high-intensity infantry programs, needs to be considered.

Clinical and Imaging Outcomes Over 12 Weeks in Elite Athletes With Early-Stage Tendinopathy

Knowledge of how to treat chronic tendinopathy has advanced in recent years, but the treatment of early tendinopathy is not well understood. The main purpose of this prospective observational study was to investigate if changes occur in clinical and imaging outcomes over 12 weeks in elite athletes with recent debut of tendinopathy. Sixty-five elite adult athletes (24 ± 5 years) with early Achilles or patellar tendinopathy (symptoms < 3 months) were examined at baseline and after 12 weeks. Patients were divided into groups based on the duration of symptoms at the time of inclusion: (T1): 0-1 month, (T2): 1-2 months, or (T3): 2-3 months. Pain-guided activity modification was the only intervention. We assessed the following clinical outcomes: Questionnaires (Victorian Institute of Sports Assessment (VISA)) and pain scores (0-10 numeric rating scale, NRS), structural outcomes from ultrasonography: Thickness, echogenicity, and Doppler flow, and from magnetic resonance imaging: Cross-sectional area (CSA), thickness and length. Tendinopathic Achilles and patellar tendons displayed no significant differences on imaging tendon structural outcomes between T1 (n = 19), T2 (n = 23), and T3 (n = 20) at baseline or after 12 weeks, with one exception: Patellar tendons in T1 were thicker than T2 and T3 at baseline. Although athletes improved clinically on VISA and most NRS scores after 12 weeks, affected tendons with greater thickness, CSA and Doppler flow than contralateral tendons at baseline remained unchanged after 12 weeks. In conclusion, these data suggest that early tendinopathy in elite athletes can improve clinically after 12 weeks while morphology remains unchanged.

The Functional Organization of Corticomotor Neurons Within the Motor Cortex Differs Among Basketball and Volleyball Athletes With Patellar Tendinopathy Compared to Asymptomatic Controls

Patellar tendinopathy (PT) typically affects jumping-sport athletes with functional impairments frequently observed. Alterations to the functional organization of corticomotor neurons within the motor cortex that project to working muscles are evident in some musculoskeletal conditions and linked to functional impairments. We aimed to determine if functional organization of corticomotor neuron projections differs between athletes with PT and asymptomatic controls, and if organization is associated with neuromuscular control. We used a cross-sectional design, and the setting was Monash Biomedical Imaging. Basketball and volleyball athletes with (n = 8) and without PT (n = 8) completed knee extension and ankle dorsiflexion force matching tasks while undergoing fMRI. We determined functional organization via identification of the location of peak corticomotor neuron activation during respective tasks (expressed in X, Y, and Z coordinates) and calculated force matching accuracy for both tasks to quantify neuromuscular control. We observed significant interactions between group and coordinate plane for functional organization of corticomotor projections to knee extensors (p < 0.001) and ankle dorsiflexors (p = 0.016). Compared to controls, PT group peak corticomotor activation during the knee extension task was 9.6 mm medial (p < 0.001) and 5.2 mm posterior (p = 0.036), and during the ankle dorsiflexion task 8.2 mm inferior (p = 0.024). In the PT group, more posterior Y coordinate peak activation location during the knee extension task was associated with greater task accuracy (r = 0.749, p = 0.034). Functional organization of corticomotor neurons differed in jumping athletes with PT compared to controls. Links between functional organization and neuromuscular control in the PT group suggest organizational differences may be relevant to knee extension neuromuscular control preservation.

Determining intracortical, corticospinal and alpha motoneurone excitability in athletes with patellar tendinopathy compared to asymptomatic controls

BACKGROUND

Lower capacity to generate knee extension maximal voluntary force (MVF) has been observed in individuals affected with patellar tendinopathy (PT) compared to asymptomatic controls. This MVF deficit is hypothesized to emanate from alterations in corticospinal excitability (CSE). The modulation of CSE is intricately linked to the excitability levels at multiple sites, encompassing neurones within the corticospinal tract (CST), intracortical neurones within the primary motor cortex (M1), and the alpha motoneurone. The aim of this investigation was to examine the excitability of intracortical neurones, CST neurones, and the alpha motoneurone, and compare these between volleyball and basketball athletes with PT and matched asymptomatic controls.

METHOD

Nineteen athletes with PT and 18 asymptomatic controls participated in this cross-sectional study. Transcranial magnetic stimulation was utilized to assess CST excitability, corticospinal inhibition (silent period, and short-interval cortical inhibition). Peripheral nerve stimulation was used to evaluate lumbar spine and alpha motoneurone excitability, including the evocation of lumbar-evoked potentials and maximal compound muscle action potential (MMAX ), and CSE with central activation ratio (CAR). Knee extension MVF was also assessed.

RESULTS

Athletes with PT exhibited longer silent period duration and greater electrical stimulator output for MMAX , as well as lower MVF, compared to asymptomatic controls (p < 0.05).

CONCLUSION

These findings indicate volleyball and basketball athletes with PT exhibit reduced excitability of the alpha motoneurone or the neuromuscular junction, which may be linked to lower MVF. Subtle alterations at specific sites may represent compensatory changes to excitability aiming to maintain efferent drive to the knee extensors.

Maximal Lower Limb Strength in Patellar Tendinopathy: A Systematic Review With Meta-Analysis

OBJECTIVE

To investigate whether lower limb strength is reduced in people with patellar tendinopathy (PT) compared with asymptomatic control individuals or the asymptomatic contralateral limb.

DATA SOURCES

MEDLINE, PubMed, Scopus, and Web of Science.

STUDY SELECTION

To be included in the systematic review and meta-analysis, studies were required to be peer reviewed, published in the English language, and case control investigations; include participants with a clinical diagnosis of PT and an asymptomatic control or contralateral limb group; and include an objective measure of lower limb maximal strength.

DATA EXTRACTION

We extracted descriptive statistics for maximal strength for the symptomatic and asymptomatic limbs of individuals with PT and the limb(s) of the asymptomatic control group, inferential statistics for between-groups differences, participant characteristics, and details of the strength-testing protocol. The risk of bias was assessed using the Joanna Briggs Institute critical appraisal tool for analytical cross-sectional studies.

DATA SYNTHESIS

Of the 23 included studies, 21 reported knee strength, 3 reported hip strength, and 1 reported ankle strength. Random-effects models (Hedges g) were used to calculate the pooled effect sizes (ESs) of muscle strength according to the direction of joint movement and type of contraction. The pooled ESs (95% CI) for maximal voluntary isometric contraction knee-extension strength, concentric knee-extension strength, and concentric knee-flexion strength were 0.54 (0.27, 0.80), 0.78 (0.30, 1.33), and 0.41 (0.04, 0.78), respectively, with all favoring greater strength in the asymptomatic control group. Researchers of 2 studies described maximal eccentric knee-extensor strength with no differences between the PT and asymptomatic control groups. In 3 studies, researchers measured maximal hip strength (abduction, extension, and external rotation), and all within-study ESs favored greater strength in the asymptomatic control group.

CONCLUSIONS

Isometric and concentric knee-extensor strength are reduced in people with PT compared with asymptomatic control individuals. In contrast, evidence for reduced eccentric knee-extension strength in people with PT compared with asymptomatic control individuals is limited and inconsistent. Although evidence is emerging that both knee-flexion and hip strength may be reduced in people with PT, more examination is needed to confirm this observation.

Time to treat the tendon rupture induced by surgery: early hypertrophy of the patellar tendon graft site predicts strong quadriceps after ACLR with bone-patellar tendon-bone autograft

PURPOSE

Quadriceps dysfunction is ubiquitous after anterior cruciate ligament reconstruction, especially when using bone-patellar tendon-bone (BPTB) autografts. The role of patellar tendon hypertrophy after graft harvest on knee extensor strength is unknown. The purpose of this study was to determine the predictive ability of patellar tendon (PT) and quadriceps muscle (Quad) cross-sectional area (CSA) on knee extensor strength 1-2 months after ACLR using BPTB autografts.

METHODS

This is a cross-sectional analysis of a cohort 1-2 months after ACLR using BPTB autograft. Peak knee extensor torque, and PT and Quad CSA measured using ultrasound imaging, were collected in 13 males and 14 females. Simple linear regressions compared quadriceps strength index (QI) against limb symmetry index (LSI) in PT and Quad CSA. Multiple linear regressions with sequential model comparisons predicting peak knee extensor torque were performed for each limb. The base model included demographics. Quad CSA was added in the first model, then PT CSA was added in the second model.

RESULTS

Both PT (p < 0.001, R2 = 0.693) and Quadriceps CSA (p = 0.013, R2 = 0.223) LSI had a positive linear relationship with QI. In the involved limb, addition of PT CSA significantly improved the model (R2 = 0.781, ΔR2 = 0.211, p for ΔR2 < 0.001). In the uninvolved limb, the addition of Quad CSA improved the model, but the addition of PT CSA did not.

CONCLUSION

PT LSI was more predictive of QI than Quad CSA LSI. Involved limb PT CSA mattered more in predicting peak knee extensor torque than did Quad CSA, but in the uninvolved limb, Quad CSA was the most important predictor of peak knee extensor torque. Graft site patellar tendon hypertrophy is key for strong quadriceps early after ACLR. Early targeted loading via exercise to promote healing of the graft site patellar tendon may bring patients a step closer to winning their battle against quadriceps dysfunction.

LEVEL OF EVIDENCE

Level I.

The Basas Spanish Squat: Superimposition of Electrical Stimulation to Optimize Patellar Tendon Strain: A Case Series

Background

The Basas Spanish Squat with electrical stimulation (E-stim) has shown promising results as a potential key exercise in treatment of athletes with patellar tendinopathy. Gold standard exercise therapy for tendon injuries consists of tendon loading exercises, or exercises that appropriately applies high levels of mechanical strain to the tendon. The theoretical pathway in which the Basas Spanish Squat with E-stim improves tendinopathy has been speculated to be the additional strain applied through the patellar tendon during superimposition of E-stim. This theory, however, has yet to be confirmed.

Purpose

The purpose of this case series was to compare patellar tendon strain, during the Basas Spanish Squat with, and without E-stim, and open kinetic chain knee extension.

Methods

Four healthy participants performed the three exercises while a physical therapist collected simultaneous unilateral ultrasound images from the patellar tendon. Strain was calculated as the change in patellar tendon length during contraction divided by the resting length.

Results

Amongst all participants, patellar tendon strain was smallest during the Basas Spanish Squat without E-stim, followed by the open kinetic chain knee extension at 60% maximum voluntary isometric contraction. The Basas Spanish Squat with E-stim yielded approximately double or more strain compared to the without E-stim condition and demonstrated higher level of strain compared to open kinetic chain knee extension in all participants.

Conclusion

The findings reflect a clear trend of increased strain through the patellar tendon when E-stim was superimposed. The results support the theory that the Basas Spanish Squat with E-stim increases patellar tendon strain and could explain the reported clinical benefits in individuals with patellar tendinopathy.

Level of Evidence

4, Case series.

Challenging the assumption of uniformity in patellar tendon structure: Regional patellar tendon morphology and mechanical properties in vivo

Patellar tendons are assumed to be uniform in morphology and mechanical properties despite a higher prevalence of tendinopathies observed in the medial region. The purpose of this study was to compare the thickness, length, viscosity, and shear modulus of the medial, central, and lateral regions of healthy patellar tendons of young males and females in vivo. B-mode ultrasound and continuous shear wave elastography were performed on 35 patellar tendons (17 females, 18 males) over three regions of interest. A linear mixed-effects model (α = 0.05) was used to determine differences between the three regions and sexes followed by pairwise comparisons for significant findings. The lateral region (mean [95% confidence interval] = 0.34 [0.31-0.37] cm) was thinner compared with the medial (0.41 [0.39-0.44] cm, p < 0.001), and central (0.41 [0.39-0.44] cm, p < 0.001) regions regardless of sex. Viscosity was lower in the lateral (19.8 [16.9-22.7] Pa-s) versus medial region (27.4 [24.7-30.2] Pa-s, p = 0.001). Length had a region-by-sex interaction (p = 0.003) characterized by a longer lateral (4.83 [4.54-5.13] cm) versus medial (4.42 [4.12-4.72] cm) region in males (p < 0.001), but not females (p = 0.992). Shear modulus was uniform between regions and sexes. The thinner, and less viscous lateral patellar tendon may reflect the lower load the tendon experiences explaining the differences in regional prevalence of developing tendon pathology. Statement of Clinical Significance: Healthy patellar tendons are not uniform in morphology or mechanical properties. Considering regional tendon properties may help guide targeted interventions for patellar tendon pathologies.

An overview of the material science and knowledge of nanomedicine, bioscaffolds, and tissue engineering for tendon restoration

Tendon wounds are a worldwide health issue affecting millions of people annually. Due to the characteristics of tendons, their natural restoration is a complicated and lengthy process. With the advancement of bioengineering, biomaterials, and cell biology, a new science, tissue engineering, has developed. In this field, numerous ways have been offered. As increasingly intricate and natural structures resembling tendons are produced, the results are encouraging. This study highlights the nature of the tendon and the standard cures that have thus far been utilized. Then, a comparison is made between the many tendon tissue engineering methodologies proposed to date, concentrating on the ingredients required to gain the structures that enable appropriate tendon renewal: cells, growth factors, scaffolds, and scaffold formation methods. The analysis of all these factors enables a global understanding of the impact of each component employed in tendon restoration, thereby shedding light on potential future approaches involving the creation of novel combinations of materials, cells, designs, and bioactive molecules for the restoration of a functional tendon.

Reliability of Continuous Shear Wave Elastography in the Pathological Patellar Tendon

OBJECTIVES

Patellar tendon injuries occur via various mechanisms such as overuse, or due to surgical graft harvest for anterior cruciate ligament reconstruction (ACLR). Quantified patellar tendon stiffness after injury may help guide clinical care. Continuous shear wave elastography (cSWE) allows for the assessment of viscosity and shear modulus in tendons. The reliability of the measure, however, has not been established in the patellar tendon. The purpose of this study was to investigate the interrater reliability, intrarater reliability, and between-day stability of cSWE in both healthy and pathological patellar tendons.

METHODS

Participants with patellar tendinopathy (n = 13), history of ACLR using bone-patellar tendon-bone autograft (n = 9), and with no history of patellar tendon injury (n = 13) were recruited. cSWE was performed 4 times by multiple raters over 2 days. Intraclass correlations (ICC) and minimum detectable change (MDC_95% ) were calculated.

RESULTS

Good to excellent between-day stability were found for viscosity (ICC = 0.905, MDC_95%  = 8.3 Pa seconds) and shear modulus (ICC = 0.805, MDC_95%  = 27.4 kPa). The interrater reliability measures, however, were not as reliable (ICC = 0.591 and 0.532).

CONCLUSIONS

cSWE is a reliable assessment tool for quantifying patellar tendon viscoelastic properties over time. It is recommended, however, that a single rater performs the measure as the interrater reliability was less than ideal.

Persons with Patellar Tendinopathy Exhibit Greater Patellar Tendon Stress during a Single-Leg Landing Task

PURPOSE

This study aimed to compare peak maximum principal stress in the patellar tendon between persons with and without patellar tendinopathy during a simulated single-leg landing task. A secondary purpose was to determine the biomechanical predictor(s) of peak maximum principal stress in the patellar tendon.

METHODS

Using finite element (FE) modeling, patellar tendon stress profiles of 28 individuals (14 with patellar tendinopathy and 14 pain-free controls) were created at the time of the peak knee extensor moment during single-leg landing. Input parameters to the FE model included subject-specific knee joint geometry and kinematics, and quadriceps muscle forces. Independent t -tests were used to compare the peak maximum principal stress in the patellar tendon and biomechanical variables used as input variables to the FE model (knee flexion, knee rotation in the frontal and transverse planes and the peak knee extensor moment) between groups. A stepwise regression model was used to determine the biomechanical predictor(s) of peak maximum principal stress in the patellar tendon for both groups combined.

RESULTS

Compared with the control group, persons with patellar tendinopathy exhibited greater peak maximum principal stress in the patellar tendon (77.4 ± 25.0 vs 60.6 ± 13.6 MPa, P = 0.04) and greater tibiofemoral joint internal rotation (4.6° ± 4.6° vs 1.1° ± 4.2°, P = 0.04). Transverse plane rotation of the tibiofemoral joint was the best predictor of peak maximum principal stress in the patellar tendon ( r = 0.51, P = 0.01).

CONCLUSIONS

Persons with patellar tendinopathy exhibit greater peak patellar tendon stress compared with pain-free individuals during single-leg landing. The magnitude of peak patellar tendon stress seems to be influenced by the amount of tibiofemoral rotation in the transverse plane.

Can we really say getting stronger makes your tendon feel better? No current evidence of a relationship between change in Achilles tendinopathy pain or disability and changes in triceps Surae structure or function when completing rehabilitation: a systematic review

OBJECTIVES

Determine if improvements in pain and disability in patients with mid-portion Achilles tendinopathy relate to changes in muscle structure and function whilst completing exercise rehabilitation.

DESIGN

A systematic review exploring the relationship between changes in pain/disability and muscle structure/function over time, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

METHODS

Six online databases and the grey literature were searched from database inception to 16th December 2022 whereas clinical trial registries were searched from database inception to 11th February 2020. We included clinical studies where participants received exercise rehabilitation (±placebo interventions) for mid-portion Achilles tendinopathy if pain/disability and Triceps Surae structure/function were measured. We calculated Cohen's d (95 % confidence intervals) for changes in muscle structure/function over time for individual studies. Data were not pooled due to heterogeneity. Study quality was assessed using a modified Newcastle-Ottawa Scale.

RESULTS

Seventeen studies were included for synthesis. No studies reported the relationship between muscle structure/function and pain/disability changes. Twelve studies reported muscle structure/function outcome measures at baseline and at least one follow-up time-point. Three studies reported improvements in force output after treatment; eight studies demonstrated no change in structure or function; one study did not provide a variation measure, precluding within group change over time calculation. All studies were low quality.

CONCLUSIONS

No studies explored the relationship between changes in tendon pain and disability and changes in muscle structure and function. It is unclear whether current exercise-based rehabilitation protocols for mid-portion Achilles tendinopathy improve muscle structure or function.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (registration number: CRD42020149970).

Relationships between surrogate measures of mechanical and psychophysiological load, patellar tendon adaptations, and neuromuscular performance in NCAA division I men's volleyball athletes

Introduction

Patellar tendon adaptations occur in response to mechanical load. Appropriate loading is necessary to elicit positive adaptations with increased risk of injury and decreased performance likely if loading exceeds the capacity of the tendon. The aim of the current study was to examine intra-individual associations between workloads and patellar tendon properties and neuromuscular performance in collegiate volleyball athletes.

Methods

National Collegiate Athletics Association Division I men's volleyball athletes (n = 16, age: 20.33 ± 1.15 years, height: 193.50 ± 6.50 cm, body mass: 84.32 ± 7.99 kg, bodyfat%: 13.18 ± 4.72%) competing across 9 weeks of in-season competition participated. Daily measurements of external workloads (i.e., jump count) and internal workloads [i.e., session rating of perceived exertion (sRPE)] were recorded. Weekly measurements included neuromuscular performance assessments (i.e., countermovement jump, drop jump), and ultrasound images of the patellar tendon to evaluate structural adaptations. Repeated measures correlations (r-rm) assessed intra-individual associations among performance and patellar tendon metrics.

Results

Workload measures exhibited significant negative small to moderate (r-rm =-0.26-0.31) associations with neuromuscular performance, negative (r-rm = -0.21-0.30), and positive (r-rm = 0.20-0.32) small to moderate associations with patellar tendon properties.

Discussion

Monitoring change in tendon composition and performance adaptations alongside workloads may inform evidence-based frameworks toward managing and reducing the risk of the development of patellar tendinopathy in collegiate men's volleyball athletes.