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Objective: To (1) develop and evaluate a machine learning model incorporating gait and physical activity to predict medial tibiofemoral cartilage worsening over 2 years in individuals without advanced knee osteoarthritis and (2) identify influential predictors in the model and quantify their effect on cartilage worsening., Design: An ensemble machine learning model was developed to predict worsened cartilage MRI Osteoarthritis Knee Score at follow-up from gait, physical activity, clinical and demographic data from the Multicenter Osteoarthritis Study. Model performance was evaluated in repeated cross-validations. The top 10 predictors of the outcome across 100 held-out test sets were identified by a variable importance measure. Their effect on the outcome was quantified by g-computation., Results: Of 947 legs in the analysis, 14% experienced medial cartilage worsening at follow-up. The median (2.5-97.5th percentile) area under the receiver operating characteristic curve across the 100 held-out test sets was 0.73 (0.65-0.79). Baseline cartilage damage, higher Kellgren-Lawrence grade, greater pain during walking, higher lateral ground reaction force impulse, greater time spent lying and lower vertical ground reaction force unloading rate were associated with greater risk of cartilage worsening. Similar results were found for the subset of knees with baseline cartilage damage., Conclusions: A machine learning approach incorporating gait, physical activity and clinical/demographic features showed good performance for predicting cartilage worsening over 2 years. While identifying potential intervention targets from the model is challenging, lateral ground reaction force impulse, time spent lying and vertical ground reaction force unloading rate should be investigated further as potential early intervention targets to reduce medial tibiofemoral cartilage worsening., Competing Interests: Competing interests: NAS reports personal fees from Tenex Health and grants from Pacira Bioscience, outside of the submitted work. AG is shareholder of BICL, LLC and consultant to Pfizer, AstraZeneca, Novartis, TissueGene, Regeneron and MerckSerono. FWR is shareholder of BICL, LLC and consultant to Grünenthal. All other authors have no competing interests to report., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY. Published by BMJ.)

Objectives: Evaluate the natural course of anterior cruciate ligament (ACL) healing on MRI within 5 years of acute ACL rupture and compare 2-year and 5-year outcomes based on healing status and treatment group., Methods: Secondary analysis of 120 Knee Anterior Cruciate Ligament Nonsurgical vs Surgical Treatment (KANON) trial participants randomised to rehabilitation and optional delayed ACL reconstruction (ACLR) or early ACLR and rehabilitation. ACL continuity on MRI (Anterior Cruciate Ligament OsteoArthritis Score 0-2) was considered evidence of ACL healing. Outcomes included Knee Injury and Osteoarthritis Outcome Score (KOOS), KOOS patient acceptable symptomatic state (PASS) and treatment failure criteria. Linear mixed models were used to estimate adjusted mean differences (95% CIs) in patient-reported sport and recreational function (KOOS-Sport/Rec) and quality of life (KOOS-QOL) at 2 and 5 years, between participants with MRI evidence of ACL healing and those who had (1) no evidence of ACL healing, (2) delayed ACLR or (3) early ACLR., Results: MRI evidence of ACL healing at 2-year follow-up was observed in 16 of 54 (30%, 95% CI 19 to 43%) participants randomised to optional delayed ACLR. Excluding participants who had delayed ACLR, 16 of 30 (53%, 36-70%) participants managed with rehabilitation-alone displayed MRI evidence of ACL healing. Two-year outcomes were better in the healed ACL group (n=16) compared with the non-healed (n=14) (mean difference (95% CI) KOOS-Sport/Rec: 25.1 (8.6-41.5); KOOS-QOL: 27.5 (13.2-41.8)), delayed ACLR (n=24) (KOOS-Sport/Rec: 24.9 (10.2-39.6); KOOS-QOL: 18.1 (5.4-30.8)) and early ACLR (n=62) (KOOS-Sport/Rec: 17.4 (4.1-30.7); KOOS-QOL: 11.4 (0.0-22.9)) groups. Five-year KOOS-QOL was better in the healed versus non-healed group (25.3 (9.4-41.2)). Of participants with MRI evidence of ACL healing, 63-94% met the PASS criteria for each KOOS subscale, compared with 29-61% in the non-healed or reconstructed groups., Conclusions: MRI appearance of ACL healing after ACL rupture occurred in one in three adults randomised to initial rehabilitation and one in two who did not cross-over to delayed ACLR and was associated with favourable outcomes. The potential for spontaneous healing of the ACL to facilitate better clinical outcomes may be greater than previously considered., Trial Registration Number: ISRCTN84752559., Competing Interests: Competing interests: EMR is deputy editor of Osteoarthritis and Cartilage, the developer of Knee injury and Osteoarthritis Outcome Score and co-founder of the Good Life with Osteoarthritis in Denmark (GLA:D) initiative to implement clinical guidelines in primary care; FWR is a shareholder of Boston Imaging Core Lab, and Consultant to Calibr and Grünenthal outside the submitted work., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objectives: To determine development of new and worsening meniscal damage over 5 years after acute anterior cruciate ligament (ACL) injury comparing rehabilitation plus early ACL reconstruction ('early-ACLR') versus rehabilitation with optional delayed ACL reconstruction ('optional-delayed-ACLR')., Methods: We used knee MRIs from the only randomised controlled trial in the field including 121 young adults. One musculoskeletal radiologist read baseline and 5-year follow-up images using the Anterior Cruciate Ligament Osteoarthritis Score (ACLOAS). We defined development (ie, new and worsening) of meniscal damage both dichotomously and as a sum score representing severity (based on the reclassified ACLOAS meniscus grades). In the full analysis set, we analysed development of meniscal damage (yes/no) with logistic regression and severity with zero-inflated Poisson regression and adjusted for age, sex and baseline meniscal damage., Results: Over 5 years, new or worsening meniscal damage developed in 45% of subjects with early-ACLR and in 53% of subjects with optional-delayed-ACLR. The relative risk for development of meniscal damage on knee level was 1.3 (95% CI 0.9 to 1.9) in optional-delayed-ACLR versus early-ACLR. For medial and lateral meniscal damage, respectively, the relative risks were 2.1 (95% CI 1.1 to 3.9) and 1.0 (95% CI 0.6 to 1.5). The mean severity score was 1.5 higher (more severe damage) on knee level in optional-delayed-ACLR versus early-ACLR (95% CI 1.1 to 1.9) among those with meniscal damage at 5 years. For medial and lateral meniscal damage, respectively, the corresponding scores were 1.7 (95% CI 1.2 to 2.5) and 1.1 (95% CI 0.8 to 1.4)., Conclusion: A strategy of early-ACLR may reduce development of medial meniscal damage following acute ACL injury. For the lateral meniscus, ACLR seems neither to be protective nor to increase the risk of damage., Trial Registration Number: ISRCTN 84752559., Competing Interests: Competing interests: FWR, one of the coauthors, is Chief Medical Officer and shareholder of BICL, LLC., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Competing Interests: Competing interests: None declared.

Background: Tendon abnormalities are prevalent among both elite and non-elite athletes. Cross-sectional imaging modalities are used to confirm and evaluate the severity of such lesions., Aim: To describe the demographics, prevalence, anatomical location and characteristics of tendon abnormalities in athletes who participated in the Rio de Janeiro 2016 Summer Olympic Games., Methods: We recorded all sports injuries reported by the National Olympic Committee (NOC) medical teams and the Organizing Committee medical staff during the Rio 2016 Summer Olympics. Diagnostic imaging was performed through the official IOC clinic within the Olympic Village, using digital ultrasound machines and 3T and 1.5T MR scanners. Image interpretation was performed centrally by board-certified musculoskeletal radiologists with expertise in sports injuries., Results: In total, 11 274 athletes (5089 women (45%), 6185 men (55%)) from 207 NOCs were included. NOC and Rio de Janeiro 2016 medical staff reported 1101 injuries. Central review of radiological images revealed 156 tendon abnormalities in 109 athletes (51.2% male, mean age: 26.8, range 18-39). The supraspinatus tendon was the most commonly involved tendon (31 cases, 19.9%), followed by the Achilles tendon (20 cases, 12.8%) and patellar and infraspinatus tendons (12 cases, 7.7%). Tendon abnormalities were most commonly seen in track and field athletes (54 abnormalities, 34.6%)., Conclusion: 156 tendon abnormalities were reported, most commonly in track and field athletes, and involving mainly the shoulder tendons, as well as Achilles and patellar tendons., Competing Interests: Competing interests: AG is the President of Boston Imaging Core Lab (BICL), and a Consultant to Merck Serono, AstraZeneca, Pfizer, GE Healthcare, OrthoTrophix, Sanofi and TissueGene. FWR and MDC are shareholders of BICL. LE is a consultant to Arthrex and Smith and Nephew., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Background: Acute muscle injuries in elite athletes are responsible for a large portion of time loss injuries., Aim: To describe the frequency, the anatomic distribution, and severity of imaging-detected acute muscle injuries among athletes who competed in the Rio de Janeiro 2016 Summer Olympics., Methods: We recorded all sports injuries reported by the National Olympic Committee medical teams and the Organising Committee medical staff during the 2016 Summer Olympics. Imaging of acute muscle injuries was performed at the IOC's polyclinic within the Olympic Village using ultrasound and 3.0 T and 1.5 T MRI scanners. The assessment of images was performed centrally by three musculoskeletal radiologists. The distribution of injuries by anatomic location and sports discipline and the severity of injuries were recorded., Results: In total, 11 274 athletes from 207 teams were included. A total of 1101 injuries were reported. Central review of radiological images revealed 81 acute muscle injuries in 77 athletes (66% male, mean age: 25.4 years, range 18-38 years). Athletics (track and field) athletes were the most commonly affected (n=39, 48%), followed by football players (n=9, 11%). The majority of injuries affected muscles from lower limbs (n=68, 84%), with the hamstring being the most commonly involved. Most injuries were grade 2 injuries according to the Peetrons classification (n=44, 54%), and we found 18 injuries exhibiting intramuscular tendon involvement on MRI., Conclusion: Imaging-detected acute muscle injuries during the 2016 Summer Olympics affected mainly thigh muscles in athletics disciplines., Competing Interests: Competing interests: AG is the president of Boston Imaging Core Lab (BICL) and a consultant to Merck Serono, AstraZeneca, Pfizer, GE Healthcare, OrthoTrophix, Sanofi and TissueGene. FWR and MDC are shareholders of BICL. LE is a consultant to Arthrex and Smith & Nephew., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Study Question: In young active adults with an acute anterior cruciate ligament (ACL) rupture, do patient reported or radiographic outcomes after five years differ between those treated with rehabilitation plus early ACL reconstruction and those treated with rehabilitation and optional delayed ACL reconstruction?, Summary Answer: At five years, patients assigned to rehabilitation plus early ACL reconstruction did not differ significantly in patient reported or radiographic outcomes from those assigned to initial rehabilitation with the option of having a later reconstruction if needed., What Is Known and What This Paper Adds: The relative efficacy of surgical reconstruction and rehabilitation for short and long term outcomes of ACL rupture is debated. Clinicians and young active adult patients should consider rehabilitation as a primary treatment option following an acute ACL tear., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Professional rugby players are prone to traumatic thoracic injuries due to the use of minimal protective gear to cover the torso. In the 2007 Rugby World Cup, thoracic injuries occurred at a rate of 8.3 cases/1000 player-hours. CT and MRI play an important role in the diagnosis of these injuries. Vital internal organs, such as the heart, lungs, trachea, liver and large blood vessels lie within close proximity to the bony structures and what seems to be a simple rib fracture or clavicular dislocation can have potentially life-threatening complications that are not detected by conventional radiography. Cross-sectional imaging helps to determine the choice of treatment. Ultrasound offers a quick and dynamic imaging examination and allows high-resolution assessment of superficial tissues that complements conventional imaging. In this review article, we (1) presented data on incidence of thoracic injuries in professional rugby players; (2) described the anatomy of the joints comprising the thoracic cage and major muscles attached to the rib cage; (3) discussed indications and relevance for MRI and presented an optimised MRI protocol for assessment of suspected thoracic injury; and (4) illustrated various types of thoracic injuries seen in professional rugby players, including sternal contusion, retrosternal haematoma, manubriosternal disruption, sternoclavicular dislocation, rib fractures and injuries of the pectoralis major muscle., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)