Inertial Measurement Units (IMUs) offer promising alternatives to traditional motion capture systems, especially in real-world sports scenarios. Accurate foot contact detection (FCD) is crucial for biomechanical analysis, and since on-the-field force plates are unsuitable, IMU-based FCD algorithms have been extensively investigated. However, sports activities leading to musculoskeletal injuries are multidirectional and high-dynamics in nature and FCD algorithms, which have mostly been studied in gait analysis, might sensibly worsen performance. This systematic review (PROSPERO, ID: CRD420251010584) aimed to evaluate IMU-based FCD algorithms applied to high-dynamics sports tasks, identifying strengths, limitations, and areas for improvement. A multi-database search was conducted until May 2025. Studies were included if they applied IMU-based FCD algorithms in high-dynamic movements. In total, 37 studies evaluating 71 FCD algorithms were included. Most papers focused on running, with only 3 on cut manoeuvres. Almost all studies involved healthy individuals only, and foot linear acceleration was the most inspected FCD metric. FCD algorithms demonstrated high accuracy, though speed variation impacted performance in 23/37 studies. This review highlights the lack of validated IMU-based FCD algorithms for high-dynamic sports movements and emphasizes the need for improved methods to advance sports biomechanics testing in injury prevention.

Anterior cruciate ligament (ACL) injuries in football mostly occur during defensive (pressing) cut maneuvers. Football-specific cutting movements are key to identifying dangerous biomechanics but hard to evaluate clinically. This study aimed to develop a practical field-based tool—Anterior Cruciate Ligament Injury Risk Profile Detection (ACL-IRD)—to assess ACL injury risk during return to sport (RTS). It was hypothesized that the ACL-IRD could detect ACL injury risk profiles after ACLR players had RTS clearance. Sixty-one footballers (21 ACLR, 40 healthy; 16.2 ± 2.2 years old, >14 months post-surgery) were tested on a regular football pitch. Players performed pre-planned (AGTT) and unplanned football-specific cut maneuvers simulating defensive pressing (FS deceiving action). Kinematic data were collected via eight wearable inertial sensors (MTw Awinda, Movella) on trunk and lower limbs. The ACL-IRD analyzed biomechanics in three risk categories, knee valgus collapse, sagittal knee loading, and trunk–pelvis imbalance, using thresholds from healthy players. A clinician-friendly, automatic report was generated. At-risk biomechanics were identified in 36–37/104 AGTT trials and 25–41/97 FS deceiving actions (at initial contact and peak knee flexion). Over 60% of risky trials involved the ACLR limb. Major risk factors were altered knee/hip flexion ratio, knee valgus, and hip abduction. The ACL-IRD is a novel, clinical-friendly tool designed to identify potential ACL injury risk profiles and is intended to support safer RTS decisions.

Precise foot contact detection (FCD) is essential for accurate biomechanical analysis in sport performance, injury prevention, and rehabilitation. This study developed and validated an inertial measurement units (IMUs)-based algorithm for FCD during sports movements. Thirty-four healthy athletes (22.8 ± 4.1 years old) performed 90° changes of direction and sprints with deceleration. Data were collected via a force platform (AMTI, 1000 Hz) and a full-body IMU suit (MTw Awinda, Movella, 60 Hz). Two IMU-based algorithms relying on pelvis vertical velocity (PVV) and resultant foot acceleration (RFA), respectively, were tested to detect initial contact (IC) and toe-off (TO). Force platform data served as the gold standard for comparison. Agreement was quantified through median offset and interquartile range (IQR); the influence of task, sex, leg, speed, and acceleration was investigated. The PVV algorithm showed higher offset than RFA for IC detection (16.7 ms vs. 10.2 ms) with comparable IQR and a substantially higher offset for TO (102.8 ms vs. 20.4 ms). Minimal influence of co-factors emerged (variance < 10%). Results were sensibly improved by combining PVV and RFA, for both IC (5.6 [70.4] ms) and TO (20.4 [78.7] ms). This algorithm offers a robust, portable alternative to force platforms, enabling accurate footstep detection and analysis of complex, sports movements in real-world environments, enhancing the ecological validity of sport assessments.

The available literature provides limited and inadequate data regarding the association between intraoperative knee kinematics, long-term clinical outcomes and survivorship after total knee arthroplasty (TKA). This study aimed to examine the potential relationship between specific intraoperative kinematics laxity assessment, acquired with a computer navigation system, and the long-term clinical outcomes and survivorship in patients undergoing TKA. This study consists of a retrospective cohort analysis of consecutive TKA procedures, in which a surgical navigation system was utilized to intra-operatively assess bone resections, implant positioning and gap balancing. The intraoperative kinematic parameters included varus-valgus laxity at 0° (VV 0) and 30° of flexion (VV 30), anterior–posterior displacement at 90° of flexion (AP 90), and passive range of motion (ROM). Different prosthesis designs were used, with a predominance of the posterior stabilized (PS)-type implant. The Knee Injury and Osteo-arthritis Outcome Score (KOOS) was used to investigate patients’ clinical and functional status. Survival was analyzed with the Kaplan–Meier method. Between-group comparisons were performed using the Mann–Whitney U test. A univariate logistic regression analysis was conducted to identify factors associated with clinical failure. Of 165 eligible patients, 120 were included in the final analysis, with a mean follow-up of 7.7 ± 2.8 years. Revision surgery was required in seven cases, representing surgical failure and an overall survival rate of 94.2%, with survival probabilities of 98.8%, 97.4%, and 93.6% at 6, 8, and 10 years, respectively. Clinical failure (KOOS < 70 in three domains) occurred in 23 patients. No intra-operative surgical parameters, including Hip-Knee-Ankle angle, Preoperative KL grade, prostheses design, VV 0, VV 30, AP 90 and ROM, or demographic variables, were found to be statistically correlated with clinical failure at follow-up. Although, in this navigated TKA cohort, survivorship was acceptable and consistent with previously reported benchmarks, it was not possible to reliably predict survival probability based solely on the intra-operative laxity parameters measured. Nevertheless, the use of surgical navigation can help surgeons accurately assess bone resections and the balance of prosthetic components.

Anterior cruciate ligament (ACL) injury risk is elevated in female youth football, yet knee joint loading has mainly been studied under controlled laboratory conditions. This limits understanding of how injury risk emerges during realistic match situations. This study provided a field-based kinetic characterization of football-specific movements by estimating knee abduction moments (KAMs) using wearable sensors and machine learning. Fifty-two highly talented female youth players performed agility tasks during training, including structured exercises (F-EX) and game-based play (F-GAME). Full-body kinematics were collected with inertial measurement units, and a validated support vector machine model, trained on synchronized motion capture and force plate data, classified trials as high or low KAM. Across 662 change-in-direction trials, 9–12% were classified as high KAM in both conditions, indicating that potentially high-risk loading regularly occurs during routine actions. High KAM trials showed reduced knee and pelvis flexion, increased hip flexion, and greater pelvis rotation toward the cutting direction, reflecting upright, stiff movement strategies. Performance analyses revealed smaller cut angles in exercises and greater approach acceleration in game play, without differences in peak velocity. These findings demonstrate the feasibility of field-based kinetic screening and support a complex-systems perspective on ACL injury risk.

Background: Anterior cruciate ligament (ACL) ruptures in soccer most commonly occur during cutting maneuvers with noncontact injury mechanisms. Biomechanical assessment of the cutting technique has become a critical component of return-to-sport (RTS) evaluation after ACL injury, particularly in young football players at elevated risk of reinjury. However, the cutting technique in players with ACL reconstruction (ACLR) has never been examined under sport-specific conditions. Purpose/Hypothesis: This study aimed to evaluate the cutting technique in pediatric soccer players who had ACLR after RTS clearance against matched healthy controls during on-field soccer (or football)-specific (FS) movements. It was hypothesized that players with ACLR would exhibit risk factors for ACL injury and biomechanical differences relative to healthy counterparts. Study Design: Case-control study; Level of evidence, 3. Methods: A total of 61 young soccer players—21 with ACLR (age, 16.7 ± 1.5 years) and 40 healthy matched controls—performed planned and unplanned FS cutting tasks on a regular soccer pitch. Kinematics of the lower limbs, pelvis, and trunk were collected using 8 wearable inertial sensors. Cut-stance phase kinematics were extracted as peak values, range of motion (ROM), initial contact values, and peak knee flexion. A linear mixed-effects model tested the effects of injury (β ₁ , ACLR vs healthy), limb (β ₂ , injured/dominant vs noninjured/nondominant), and their interaction effect (β ₂ + β ₃ , injury × limb) on kinematics ( P < .05). Results: Significant injury × limb interactions ( R ² : 0.02-0.41; P < .001- P < .046) indicated altered kinematics in players with ACLR compared with healthy controls. Players with ACLR showed greater peak hip flexion (β ₁ = 22.2°), knee valgus (β ₁ = 2.3°), and lower knee flexion (β ₁ = −2.6°) during the unplanned FS task. Players with ACLR also showed reduced lower limb flexion ROM (β ₁ = −19.6° to −10.6°) but greater pelvis and trunk flexion ROM (β ₁ = 2.2° to 4.8°) during unplanned FS task and greater contralateral pelvic drop and trunk tilt (β ₁ = −2.9° to −3.7°) in both tasks. Conclusion: Players with ACLR showed biomechanical alterations during field-based sport-specific cutting maneuvers compared with matched healthy controls, despite RTS clearance.