BACKGROUND:Limited information is available about factors that impact prognosis after quadriceps muscle strain injury, particularly injuries involving the rectus femoris. This study aims to determine whether baseline clinical and radiological findings are associated with time to return to play (RTP) and injury recurrence after rectus femoris muscle strain injury in elite Australian Football players. HYPOTHESIS:Baseline magnetic resonance imaging (MRI) findings related to the specific anatomical location and severity of rectus femoris injury will influence time to RTP and recurrence. STUDY DESIGN:Cross sectional study. LEVEL OF EVIDENCE:Level 4. METHODS:A total of 163 quadriceps muscle strain injuries from 127 elite Australian Football players were analyzed. The impact of clinical (player characteristics, injury mechanism, injury type) and MRI findings (anatomical location of injury, injury severity) on RTP and injury recurrence were explored using time to event (survival) analyses. RESULTS:RTP time frames (means and standard deviations) were longest for injuries affecting the rectus femoris proximal free tendon (50.4 ± 16.2 days) and central aponeurosis (33.7 ± 20.4 days). Central aponeurosis injuries with disruption took longer to RTP compared with central aponeurosis injuries without disruption (hazard ratio [HR] = 0.47; P = 0.03), and longer than injuries involving the anterior (HR = 0.59; P = 0.05) or posterior aponeuroses (HR = 0.56; P = 0.02). Increased severity of aponeurotic disruption was also associated with prolonged RTP (P < 0.01). Reinjuries were associated with longer RTP than index injuries (adjusted HR = 0.49; P = 0.04). No clinical or MRI factors were associated with injury recurrence. CONCLUSION:Rectus femoris injuries with significant connective tissue disruption, particularly those affecting the proximal free tendon or central aponeurosis, as well as reinjuries, may require extended time for rehabilitation and RTP. CLINICAL RELEVANCE:An understanding of baseline MRI findings related to the specific anatomical location and severity of connective tissue disruption can enhance the ability of clinicians to estimate expected RTP time frames after rectus femoris injury.

Understanding factors associated with early hip osteoarthritis (OA) in young active adults may facilitate hip OA prevention. We investigated the cross-sectional association between hip contact force (HCF) during walking and cartilage defect severity, accounting for cam morphology size (alpha angle), hip pain severity, sex, age, and walking speed, in football players with hip/groin pain. One hundred and twenty-one football players (18-50 years; 26 women) with > 6-month hip/groin pain and no radiographic OA underwent MRI and a Dunn 45° radiograph. Outcome: Scoring Hip Osteoarthritis with MRI (SHOMRI) score for cartilage defect severity (0-20), categorized into three SHOMRI groups: (a) SHOMRI = 0; (b) SHOMRI = 1-3; and (c) SHOMRI = 4+. Movement and ground force data were captured whilst participants walked at their self-selected pace. Musculoskeletal modeling was used to calculate HCF for one stride cycle. The exposure variable was HCF impulse (body weight times seconds [BW.s]). Differences in HCF impulse based on SHOMRI group (for the most symptomatic hip) were assessed using linear models, controlling for alpha angle, sex, age, walking speed, hip pain, and contralateral hip pain status. Resultant HCF impulse was significantly higher for participants in the 0 versus 4+ SHOMRI group (mean difference; 95%CI: 0.142BW.s; 0.028-0.256 for swing and 0.106BW.s; 0.029-0.184 for stance) and 0 versus 1-3 SHOMRI group (0.071 BW.s; 0.016-0.125 for swing). Participants with more severe cartilage defects walked with lower hip joint loading, and other variables (e.g., alpha angle size, hip pain severity, age) contributed little to this relationship. Hip joint under-loading could be a possible target for hip OA prevention.

Hamstring strain injuries (HSI) are common in field-based sports. Musculoskeletal modeling studies have been used to investigate hamstring mechanics during steady-state running. Accelerative and decelerative running as well as change of direction actions, which are common mechanisms of HSI, have been largely overlooked. Therefore, the aim of the present study was to investigate the mechanics of the biarticular hamstrings during acceleration, deceleration, and sidestep cutting tasks. Three-dimensional motion analysis, ground reaction force and electromyography data were collected for 20 recreationally active adults performing acceleration, deceleration and 45-degree sidestep cutting. Musculoskeletal modeling was used to solve for musculotendinous (MTU) force, stretch, and work. Peak MTU force occurred during acceleration for biceps femoris long head (1.5 body weights (BW)) and semimembranosus (2.7 BW), whereas it occurred during deceleration for semitendinosus (0.7 BW). Peak stretch was highest in deceleration for all hamstrings (10.9% to 13.7%), followed by sidestep cutting (8.9% to 12.4%) then acceleration (5.5% to 10.2%). The greatest negative work performed by biceps femoris long head occurred during acceleration and sidestep cutting (-0.25 J·kg-1) but occurred during sidestep cutting for semimembranosus (-0.50 J·kg-1) and deceleration for semitendinosus (-0.12 J·kg-1). Acceleration, deceleration and sidestep cutting impose substantial demands on the hamstrings. Deceleration imposed the largest kinematic (i.e., stretch) demand on all hamstrings, whilst the task imposing the greatest kinetic demands (i.e., force and negative work) varied depending on the individual hamstring. These findings may help to inform HSI preventative and return-to-sport strategies.

OBJECTIVE:We evaluated the effect of physiotherapist-led treatment with targeted-strengthening (STRENGTH) compared with physiotherapist-led treatment with standardised-stretching (STRETCH) on hip-related quality of life (QOL) and patient-perceived Global Rating of Change (GROC) at 6 months in people with femoroacetabular impingement (FAI) syndrome. METHODS:Assessor-blind, limited disclosure, parallel, superiority randomised controlled trial. Participants aged 18-50 years with FAI syndrome were recruited and randomly allocated (1:1 ratio) to receive 6 months of STRENGTH or STRETCH treatment. Primary outcomes were change in (1) hip-related QOL (International Hip Outcome Tool-33 (iHOT-33, 0-100 points)); and (2) GROC-pain and GROC-function at 6 months. Secondary analysis included dichotomised GROC ('improved' and 'not improved') and hip muscle strength. Analyses were by intention to treat. RESULTS:154 participants (STRENGTH n=79 (53% women, mean 35 (SD 9) years); STRETCH n=75 (45% women, mean 36 (SD 9) years)) were included. There was no difference between groups for change in hip-related QOL (mean difference (95% CI) 0.2 (-5.9 to 6.3)) or patient-perceived global improvement (GROC-pain 0.2 (-0.2 to 0.7), p=0.23; GROC-function 0.3 (-0.1 to 0.6)) at 6 months. 72% of STRENGTH were improved for GROC-pain (OR 2.36 (1.15 to 4.84)) compared with 52% of STRETCH. STRENGTH had greater improvements than STRETCH in hip strength. Both groups improved in iHOT-33 over 6 months (STRENGTH 19.2 (15.7 to 22.8), STRETCH 20.8 (17.1 to 24.5) points). CONCLUSION:There was no superior physiotherapist-led treatment to improve hip-related QOL in people with FAI syndrome, but secondary analysis indicated that targeted strengthening resulted in greater improvements in perceived pain and hip muscle strength at 6 months. Hip-related QOL improved in both groups by clinically meaningful amounts. TRIAL REGISTRATION NUMBER:ACTRN12617001350314.

This study aimed to describe and compare the characteristics of runs performed by a cohort of male and female runners, with and without a history of knee surgery. Data on frequency, distance, pace and cadence were collected from 227 runners (45% females, 48% knee surgery) using smartwatches over 4 years (n = 114,324 runs). Generalised mixed models compared running characteristics between sex and knee surgery strata. Runners typically performed 2-5 runs per week between 3.5-20 km in length, 4-7 min/km pace, at 160-180 steps/min cadence. Comparing group averages, males ran faster (0.78 fewer min/km, 95% CI 0.55 to 1.0), and further distances (13% longer, [4% to 22%]). Average run frequency and cadence did not differ between males and females. Surgical group ran less frequently on average (66% longer gaps, [14% to 142%]), shorter distances (10% shorter, [17% to 2% shorter]), at slower pace (0.29 more min/km, [0.06 to 0.52]), with lower cadence (4.32 fewer steps/min, [0.73 to 7.91 fewer]). Despite group-level differences, sex and surgical history had limited ability to explain variations in running behaviours, with the majority of variance attributed to participant-level effects (29-53%). Runners within sex and knee surgery sub-groups should not be considered homogenous cohorts.

Identifying biomechanical impairments in young, physically active populations with hip/groin pain is crucial for early intervention. This study characterized the biomechanical features of a novel task, the step-down-and-pivot, in competitive football players, comprising 36 individuals with hip/groin pain (28 ± 6 years) and 11 controls (26 ± 4 years). Experimental motion data and ground forces were input into biomechanical models to calculate joint angles and moments, then transformed into principal components and input into a feature selection pipeline. Ten main biomechanical features were identified for each limb, i.e. the pivot limb and the swing limb, that could discriminate between symptomatic and control groups with p < 0.05. In symptomatic individuals, the main features were as follows: pivot limb: smaller hip flexion and knee extension angles, delayed initiation of hip flexion and increased ankle dorsiflexion moment; swing limb: reduced hip flexion moment, increased hip internal rotation moment, delayed hip adduction and knee extension moments, and reduced ankle dorsiflexion angle. The largest group differences occurred during the transitions from step-down to pivot, and pivot to step-forward, supporting a potential role for multi-phase and/or multi-planar tasks when assessing biomechanical impairments due to hip/groin pain. Although biomechanical alterations in our symptomatic participants were small, they could be identified and characterized using feature selection.

Objectives:To evaluate the onset, frequency and time loss impact of recurrent calf muscle strain injuries in elite male Australian football players over a decade. To explore how outcomes are affected by alternative recurrence definitions. Method:Calf muscle strain injuries were reported to the Soft Tissue Injury Registry of the Australian Football League (2014-2023). Cases were categorised as index versus recurrent injuries. Alternate recurrence definitions varied based on: (1) timing (ie, subsequent injuries occurring before or after full recovery (a return to full training) and (2) location (ie, subsequent injuries involving the same side but not necessarily same muscle vs only those confirmed to involve the same muscle). Results:563 injuries in 359 players were evaluated. Recurrences resulted in ≥2153 total days lost over 10 years and ≥35.6 days lost on average per injury. Recurrence frequencies within 2 years (13%-21.3%), within the same season (7.5%-13.9%) and within 2 months (2.9%-7.3%) varied depending on the definition. 20% of all subsequent injuries occurred before full recovery, and these injuries took on average 46.7±25.6 days to return to play. Conclusions:Recurrent calf muscle strain injuries in elite male Australian football players commonly have prolonged time loss, irrespective of timing or location. A 2-year recurrence susceptibility is consistent across onsets, and cases that fail early can have a large impact when accounted for. We need to 'talk the same language' in research and practice to better understand and prevent recurrences for a given type of injury across different sports and sporting levels.

OBJECTIVE: To describe the injury type (index/recurrent), location (medial head/lateral head), mechanism, player demographics, and prognosis (recovery/recurrence) in gastrocnemius injuries affecting elite male players. DESIGN: Longitudinal cohort. METHODS: Injury data from 2014 to 2023 were extracted from the Soft Tissue Injury Registry of the Australian Football League. Data items were injury type and circumstances, player demographics, and prognostic outcomes (functional milestones and recurrence). Demographics, injury characteristics, and prognoses were described. Recovery (time to return to play) was compared (survival analysis) for injury type (index vs recurrent), location (medial head vs lateral head), mechanism, intrinsic factors, and training history. RESULTS: Eighty-two magnetic resonance imaging-confirmed gastrocnemius injuries were included (68 index, 14 recurrent). Medial head injuries were most prevalent (78%). The median (interquartile range) time to reach functional milestones was 3 days (3) to walk pain free, 14 days (11) to run at >90% of the maximum speed, 14 days (15.5) to return to full training, and 19 days (16) to return to play. A recent change in loading prior to injury (P = .02), a running-related mechanism (P = .03), and older age (P = .01) resulted in longer recovery. Acceleration was the most common running injury mechanism, occurring in 13 cases. Twenty-nine injuries lacked a specific inciting mechanism. Recurrences occurred <6 months after the index injury in 79% (n = 11) of cases. CONCLUSION: Gastrocnemius injuries predominantly affected the medial head. More than 1 in 6 cases were recurrent. J Orthop Sports Phys Ther 2025;55(10):1-8. Epub 8 September 2025. doi:10.2519/jospt.2025.13526.

Early identification of altered movement patterns can guide interventions for young adults with hip and/or groin pain. Characterising dynamic stability during movement tasks is a unique approach to understanding these altered biomechanics associated with hip and/or groin pain. We quantified two measures of stability: Margin of Stability (MoS); and Whole-Body Angular Momentum (WBAM), during the landing period of the single-leg drop jump for 117 young adult football players with hip/groin pain (27 ± 4 years) and 24 asymptomatic controls (27 ± 6 years). Experimental motion data, ground forces and associated centres-of-pressure were input into biomechanical models to calculate segmental and centre-of-mass kinematics, and subsequently, to calculate MoS and WBAM. Symptomatic individuals demonstrated significantly more positive mediolateral MoS during the early braking phase (0-31% of landing). The sagittal-plane WBAM differed significantly between groups near the transition from braking to propulsion (35-51% of landing) and at take-off (98-100% of landing) due to a lag in torso angular momentum. Whilst differences were small, our findings suggest that symptomatic individuals adopted a conservative landing strategy in which regulating mediolateral MoS appeared to be prioritised over sagittal-plane WBAM. Overall, the analysis of dynamic stability provided new insights into altered biomechanics in the presence of joint pain/pathology.

INTRODUCTION:This double-blind, randomised controlled trial (RCT) aims to estimate the effect of a physiotherapist-led intervention with targeted strengthening compared with a physiotherapist-led intervention with standardised stretching, on hip-related quality of life (QOL) or perceived improvement at 6 months in people with femoroacetabular impingement (FAI) syndrome. We hypothesise that at 6 months, targeted strengthening physiotherapist-led treatment will be associated with greater improvements in hip-related QOL or greater patient-perceived global improvement when compared with standardised stretching physiotherapist-led treatment.METHODS AND ANALYSIS:We will recruit 164 participants with FAI syndrome who will be randomised into one of the two intervention groups, both receiving one-on-one treatment with the physiotherapist over 6 months. The targeted strengthening physiotherapist-led treatment group will receive a personalised exercise therapy and education programme. The standardised stretching physiotherapist-led treatment group will receive standardised stretching and personalised education programme. Primary outcomes are change in hip-related QOL using International Hip Outcome Tool-33 and patient-perceived global improvement. Secondary outcomes include cost-effectiveness, muscle strength, range of motion, functional task performance, biomechanics, hip cartilage structure and physical activity levels. Statistical analyses will make comparisons between both treatment groups by intention to treat, with all randomised participants included in analyses, regardless of protocol adherence. Linear mixed models (with baseline value as a covariate and treatment condition as a fixed factor) will be used to evaluate the treatment effect and 95% CI at primary end-point (6 months).ETHICS AND DISSEMINATION:The study protocol was approved (La Trobe University Human Ethics Committee (HEC17-080)) and prospectively registered with the Australian New Zealand Clinical Trials Registry. The findings of this RCT will be disseminated through peer reviewed scientific journals and conferences. Patients were involved in study development and will receive a short summary following the completion of the RCT.TRIAL REGISTRATION NUMBER:ACTRN12617001350314.

Background: Differences in walking biomechanics between women and men with patellofemoral joint (PF) osteoarthritis (OA) may contribute to the development or progression of persistent symptoms in people with PFJ OA. Objective: Evaluate how walking biomechanics of women with PF OA differ from: (i) men with PFJ OA; and (ii) women without PF OA. Second, explore the relationship between knee-related symptoms/function and walking biomechanics in individuals with PF OA, and whether these are modified by sex. Methods: Sixty-seven individuals with PF OA (43 women) and 14 women without PF OA were included. Biomechanics data were recorded during walking. Patient-reported symptoms and function were obtained using the Knee injury and Osteoarthritis Outcome Score. Differences in continuous biomechanical data were assessed using statistical parametric mapping, with discrete data and relationships evaluated using linear models. Results: Women with PF OA walked with a greater hip adduction angle throughout stance (t > 2.757) and lower impulses for the hip flexion, knee flexion, and ankle dorsiflexion moments (adjusted mean differences [95 % CI]:3.3 x 10(-2) [-4.9 x 10(-2), -1.6 x 10(-2)], -2.9 x 10(-2) [-5.3 x 10(-2), -0.4 x 10(-2)], -5.1 x 10(-2) [-8.2 x 10(-2), -2.0 x 10(-2)] Nms/kg, respectively) compared to men with PF OA. Compared to their asymptomatic peers, women with PF OA displayed a 5 degrees offset towards greater hip flexion. Higher knee adduction moment impulse correlated with worse KOOS-ADL scores in men, not women. Conclusion: Observed biomechanical differences were small in nature with moderate to weak relationship observed with the KOOS. Findings were not limited to the knee, indicating that women with PF OA display unique biomechanical features across the kinetic-chain.

OBJECTIVE:To describe the epidemiology of quadriceps muscle strain injury (QMSI) in elite Australian Football League (AFL) players, explore recovery milestones and determine whether recovery is impacted by factors such as injury type (index vs. re-injury), the primary muscle injured and the mechanism of injury.MEASURES:All QMSI data reported to the Soft Tissue Injury Registry of the AFL from the 2014 to 2020 seasons were evaluated. Player demographic data, circumstances of injury, MRI reports and recovery outcomes following injury were extracted. Descriptive statistics and frequency distributions are presented. Recovery outcomes for injury type, primary muscle injured and the mechanism of injury were compared using univariate analyses.RESULTS:There were 164 QMSIs from 122 players reported (134 index; 30 re-injuries). Almost all (91.3%) QMSIs involved the rectus femoris. Half (48.4%) of the QMSIs occurred during kicking and most commonly affected the dominant kicking leg (72%). The majority occurred at training (64.6%). All re-injuries involved the rectus femoris, most occurred from kicking (63.0%) and within 6 months of the preceding injury (70%). The mean return to play (RTP) time was 25.4 days (95%CI = 22.6-28.2) and rectus femoris injuries took around 14 days longer to RTP than vastii injuries (p = 0.001). QMSIs with a kicking mechanism took the longest to RTP of all injury mechanisms.CONCLUSION:In AFL players, QMSIs occur mostly in the dominant leg from a kicking mechanism. Rectus femoris injuries are more prevalent and result in longer RTP time frames. Re-injuries exclusively involved the rectus femoris, primarily from kicking.

IntroductionMaximal acceleration and deceleration tasks are frequently required in team sports, often occurring rapidly in response to external stimuli. Accelerating and decelerating can be associated with lower limb injuries; thus, knowledge of joint mechanics during these tasks can improve the understanding of both human high performance and injury mechanisms. The current study investigated the fundamental differences in lower limb joint mechanics when accelerating and decelerating by directly comparing the hip, knee, and ankle joint moments and work done between the two tasks.MethodsTwenty participants performed maximal effort acceleration and deceleration trials, with three-dimensional marker trajectories and ground reaction forces collected simultaneously. Experimental data were combined with inverse dynamics analysis to compute joint moments and work.ResultsNet joint work for all lower limb joints was positive during acceleration and negative during deceleration. This occurred because of significantly greater positive work production from the ankle and hip during acceleration and significantly greater negative work production from all joints during deceleration. The largest contributions to positive work during acceleration came from the ankle, followed by the hip and knee joints, whereas the largest contributions to negative work during deceleration came from the knee and hip joints, followed by the ankle. Peak joint moments were significantly greater when decelerating compared with accelerating, except for the peak ankle plantarflexion and hip flexion moments, which were significantly greater when accelerating.ConclusionsOur findings may help to guide training interventions, which aim to enhance the performance of acceleration and deceleration tasks, while also mitigating the associated injury risk.

Introduction Running is one of the most popular recreational activities worldwide, due to its low cost and accessibility. However, little is known about the impact of running on knee joint health in runners with and without a history of knee surgery. The primary aim of this longitudinal cohort study is to compare knee joint structural features on MRI and knee symptoms at baseline and 4-year follow-up in runners with and without a history of knee surgery. Secondary aims are to explore the relationships between training load exposures (volume and/or intensity) and changes in knee joint structure and symptoms over 4 years; explore the relationship between baseline running biomechanics, and changes in knee joint structure and symptoms over 4 years. In addition, we will explore whether additional variables confound, modify or mediate these associations, including sex, baseline lower-limb functional performance, knee muscle strength, psychological and sociodemographic factors.Methods and analysis A convenience sample of at least 200 runners (sex/gender balanced) with (n=100) and without (n=100) a history of knee surgery will be recruited. Primary outcomes will be knee joint health (MRI) and knee symptoms (baseline; 4 years). Exposure variables for secondary outcomes include training load exposure, obtained daily throughout the study from wearable devices and three-dimensional running biomechanics (baseline). Additional variables include lower limb functional performance, knee extensor and flexor muscle strength, biomarkers, psychological and sociodemographic factors (baseline). Knowledge and beliefs about osteoarthritis will be obtained through predefined questions and semi-structured interviews with a subset of participants. Multivariable logistic and linear regression models, adjusting for potential confounding factors, will explore changes in knee joint structural features and symptoms, and the influence of potential modifiers and mediators.Ethics and dissemination Approved by the La Trobe University Ethics Committee (HEC-19524). Findings will be disseminated to stakeholders, peer-review journals and conferences.

BACKGROUND:Femoroacetabular impingement (FAI) syndrome is considered a motion-related condition. Little is known about the influence of symptom severity and cam morphology on hip biomechanics for individuals with FAI syndrome. RESEARCH QUESTION:Are hip biomechanics during running associated with symptom severity or cam morphology size in male football players with FAI syndrome? METHODS:Forty-nine male, sub-elite football (soccer or Australian football) players (mean age= 26 years) with FAI syndrome completed the International Hip Outcome Tool-33 (iHOT-33) and Copenhagen Hip and Groin Outcome Score (HAGOS) and underwent radiographic evaluation. Biomechanical data were collected during overground running (3-3.5 m∙s-1) using three-dimensional motion capture technology and an embedded force plate. Various discrete hip angles and impulses of joint moments were analysed during the stance phase. Linear regression models investigated associations between running biomechanics data (dependent variables) and iHOT-33 and HAGOS scores and cam morphology size (independent variables). RESULTS:Hip joint angles during running were not associated with symptom severity in football players with FAI syndrome. A positive association was found between the impulse of the hip external rotation moment and HAGOS-Sport scores, such that a smaller impulse magnitude occurred with a lower HAGOS-Sport score (0.026 *10-2 [95%CI <0.001 *10-2 to 0.051 *10-2], P = 0.048). Larger cam morphology was associated with a greater peak hip adduction angle at midstance (0.073 [95%CI 0.002-0.145], P = 0.045). SIGNIFICANCE:Hip biomechanics during running did not display strong associations with symptom severity or cam morphology size in male football players with FAI syndrome who were still participating in training and match play. Future studies might consider investigating associations during tasks that utilise end range hip joint motion or require greater muscle forces.

Patellofemoral joint (PFJ) osteoarthritis is common following anterior cruciate ligament reconstruction (ACLR) and may be linked with altered joint loading. However, little is known about the cross-sectional and longitudinal relationship between PFJ loading and osteoarthritis post-ACLR. This study tested if altered PFJ loading is associated with prevalent and worsening early PFJ osteoarthritis post-ACLR. Forty-six participants (mean +/- 1 SD age 26 +/- 5 years) approximately 1-year post-ACLR underwent magnetic resonance imaging (MRI) and biomechanical assessment of their reconstructed knee. Trunk and lower-limb kinematics plus ground reaction forces were recorded during the landing phase of a standardized forward hop. These data were input into a musculoskeletal model to calculate the PFJ contact force. Follow-up MRI was completed on 32 participants at 5-years post-ACLR. Generalized linear models (Poisson regression) assessed the relationship between PFJ loading and prevalent early PFJ osteoarthritis (i.e., presence of a PFJ cartilage lesion at 1-year post-ACLR) and worsening PFJ osteoarthritis (i.e., incident/progressive PFJ cartilage lesion between 1- and 5-years post-ACLR). A lower peak PFJ contact force was associated with prevalent early PFJ osteoarthritis at 1-year post-ACLR (n = 14 [30.4%]; prevalence ratio: 1.37; 95% confidence interval [CI]: 1.02-1.85) and a higher risk of worsening PFJ osteoarthritis between 1- and 5-years post-ACLR (n = 9 [28.1%]; risk ratio: 1.55, 95% CI: 1.13-2.11). Young adults post-ACLR who exhibited lower PFJ loading during hopping were more likely to have early PFJ osteoarthritis at 1-year and worsening PFJ osteoarthritis between 1- and 5-years. Clinical interventions aimed at mitigating osteoarthritis progression may be beneficial for those with signs of lower PFJ loading post-ACLR.

Objective: To test whether quadriceps strength is associated with measures of patellofemoral (PF) joint loading during running and hopping in people after an anterior cruciate ligament reconstruction (ACLR). Design: Cross-sectional study. Setting: Biomechanics laboratory. Participants: Sixty-five participants (24 women; 41 men) 1-2 years post-ACLR. Main outcome measures: Peak isometric quadriceps strength for the surgical limb was measured using a dynamometer. Motion analysis and ground reaction force data were combined with musculoskeletal modelling to measure PF joint loading variables for the reconstructed knee (peak knee flexion angle; peak/impulse of the PF joint contact force; time to peak PF joint contact force) during the stance phase of running and during the landing phase of a standardised forward hop. Linear regression analysis (adjusting for age and sex) assessed the association between quadriceps strength and PF joint loading variables. Results: Two significant, albeit modest, associations were revealed. Quadriceps strength was associated with the time to peak PF joint contact force during running (13 = -0.001; 95%CI -0.002 to -0.000; R2 = 0.179) and the impulse of the PF joint contact force during hopping (13 = 0.014; 95%CI 0.003 to 0.024; R2 = 0.159). Conclusions: A strong link between quadriceps strength and PF joint loading was not evident in people 1-2 years post-ACLR.

Landing manoeuvres are an integral task for humans, especially in the context of sporting activities. Such tasks often involve landing on one leg which requires the coordination of multiple muscles in order to effectively dissipate kinetic energy. However, no prior studies have provided a detailed description of the strategy used by the major lower limb muscles to perform single-leg landing. The purpose of the present study was to understand how humans coordinate their lower limb muscles during a single-leg landing task. Marker trajectories, ground reaction forces (GRFs), and surface electromyography (EMG) data were collected from healthy male participants performing a single-leg landing from a height of 0.31 m. An EMG-informed neuromusculoskeletal modelling approach was used to generate neuromechanical simulations of the single-leg landing task. The muscular strategy was determined by computing the magnitude and temporal characteristics of musculotendon forces and energetics. Muscle function was determined by computing muscle contributions to lower limb net joint moments, GRFs and lower limb joint contact forces. It was found that the vasti, soleus, gluteus maximus and gluteus medius produced the greatest muscle forces and negative (eccentric) mechanical work. Downward momentum of the centre-of-mass was resisted primarily by the soleus, vasti, gastrocnemius, rectus femoris, and gluteus maximus, whilst forward momentum was primarily resisted by the quadriceps (vasti and rectus femoris). Flexion of the lower limb joints was primarily resisted by the uni-articular gluteus maximus (hip), vasti (knee) and soleus (ankle). Overall, our findings provide a unique insight into the muscular strategy used by humans during a landing manoeuvre and have implications for the design of athletic training programs.

Background Despite calf muscle strain injuries (CMSI) being problematic in many sports, there is a dearth of research to guide clinicians dealing with these injuries. The aim of this study was to evaluate the current practices and perspectives of a select group of international experts regarding the assessment, management and prevention of CMSI using in-depth semi-structured interviews. Results Twenty expert clinicians working in elite sport and/or clinician-researchers specialising in the field completed interviews. A number of key points emerged from the interviews. Characteristics of CMSI were considered unique compared to other muscle strains. Rigor in the clinical approach clarifies the diagnosis, whereas ongoing monitoring of calf capacity and responses to loading exposure provides the most accurate estimate of prognosis. Athlete intrinsic characteristics, injury factors and sport demands shaped rehabilitation across six management phases, which were guided by key principles to optimise performance at return to play (RTP) while avoiding subsequent injury or recurrence. To prevent CMSI, periodic monitoring is common, but practices vary and data are collected to inform load-management and exercise selection rather than predict future CMSI. A universal injury prevention program for CMSI may not exist. Instead, individualised strategies should reflect athlete intrinsic characteristics and sport demands. Conclusions Information provided by experts enabled a recommended approach to clinically evaluate CMSI to be outlined, highlighting the injury characteristics considered most important for diagnosis and prognosis. Principles for optimal management after CMSI were also identified, which involved a systematic approach to rehabilitation and the RTP decision. Although CMSI were reportedly difficult to prevent, on- and off-field strategies were implemented by experts to mitigate risk, particularly in susceptible athletes.

Background Despite being a common cause of time loss, information regarding best practice for calf muscle strain injuries (CMSI) in sport is scarce. Objective To establish best practice for the assessment and management of CMSI. Design Qualitative. Setting In-depth interviews. Patients (or Participants) 20 expert medical professionals working in elite sport and/or researchers specialising in the field; representing seven countries and seven sports. Interventions (or Assessment of Risk Factors) Semi-structured interviews using a schedule of questions canvassing pre-identified topics. Thematic coding to analyse findings. Main Outcome Measurements Data were evaluated in three key areas: (i) injury characteristics, (ii) injury management, and (iii) injury prevention. Results CMSI have unique injury characteristics compared to other common muscle strain injuries (e.g. hamstring), but a criteria-based approach can assist forming the most accurate impression of prognosis. Similarly, a structured approach should be followed to ensure the athlete returns to a high level of performance and the risk of re-injury is minimized, focusing on: re-strengthening, plyometric and ballistic exercises, as well as running-based reconditioning specific to the sport. For the best chance to prevent index CMSI, strategies should span multiple domains of athlete management: screening and monitoring, field-based exposure (e.g. workload data), and off-field interventions (e.g. strengthening). Injury prevention strategies should be tailored to the individual, considering extrinsic (the sport, position played, club culture/coach expectations) and intrinsic (previous injury history, age, training history) factors that may increase susceptibility to CMSI. Conclusions Knowledge about the unique injury characteristics of CSMI can clarify the likely prognosis and best approach to rehabilitation. Practitioners attempting to prevent CMSI should use a multi-faceted approach given that the aetiology of CMSI is complex and often unique to the individual.