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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. [ABSTRACT FROM AUTHOR]

Purpose: Patellofemoral pain syndrome and patellar tendinopathy are important running-related overuse injuries. This study investigated the interaction of running speed and step frequency alterations on peak and cumulative patellofemoral joint stress (PFJS) and patellar tendon force (PTF) parameters. Methods: Twelve healthy individuals completed an incremental running speed protocol on a treadmill at habitual, increased and decreased step frequency. Peak PFJS and PTF, peak rate of PFJS and PTF development, and PFJS and PTF impulse per kilometer (km) were calculated using musculoskeletal modeling. Results: With increasing running speed, peak PFJS (P < 0.001) and PTF (P < 0.001) and peak rate of PFJS (P < 0.001) and PTF (P < 0.001) development increased, whereas PFJS (P < 0.001) and PTF (P < 0.001) impulse per km decreased. While increasing step frequency by 10%, the peak PFJS (P < 0.001) and PTF (P < 0.001) and the PFJS (P < 0.001) and PTF (P < 0.001) impulse per kilometer decreased. No significant effect of step frequency alteration was found for the peak rate of PFJS (P = 0.008) and PTF (P = 0.213) development. A significant interaction effect was found for PFJS (P <0.001) and PTF (P <0.001) impulse per km, suggesting that step frequency alteration was more effective at low running speed. Conclusions: The effectiveness of step frequency alteration on PFJS and PTF impulse per km is dependent on the running speed. With regard to peak PFJS and PTF, step frequency alteration is equally effective at low and high running speeds. Step frequency alteration was not effective for peak rate of PFJS and PTF development. These findings can assist the optimization of patellofemoral joint and patellar tendon load management strategies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: It is unknown why some athletes develop patellar tendinopathy and others do not, even when accounting for similar workloads between individuals. Genetic differences between these two populations may be a contributing factor. The purpose of this work was to screen the entire genome for genetic markers associated with patellar tendinopathy. Methods: Genome-wide association (GWA) analyses were performed utilizing data from the Kaiser Permanente Research Board (KPRB) and the UK Biobank. Patellar tendinopathy cases were identified based on electronic health records from KPRB and UK Biobank. GWA analyses from both cohorts were tested for patellar tendinopathy using a logistic regression model adjusting for sex, height, weight, age, and race/ethnicity using allele counts for single nucleotide polymorphisms. The data from the two GWA studies (KPRB and UK Biobank) were combined in a meta-analysis. Results: There were a total of 1670 cases of patellar tendinopathy and 293,866 controls within the two cohorts. Two single nucleotide polymorphisms located in the intron of the cytochrome c oxidase assembly factor 1 (COA1) gene showed a genome-wide significant association in the meta-analysis. Conclusions: Genetic markers in COA1 seem to be associated with patellar tendinopathy and are potential risk factors for patellar tendinopathy that deserve further validation regarding molecular mechanisms. [ABSTRACT FROM AUTHOR]

Purpose: Although male volleyball players report a greater prevalence of patellar tendinopathy than female players, it remains unknown whether higher patellar tendon loading generated during landing by male players is related to sex-specific neuromuscular recruitment patterns. This study aimed to investigate the relationship between neuromuscular recruitment patterns and patellar tendon loading during landing and to determine whether there were any significant differences in lower limb neuromuscular recruitment patterns displayed by male and female volleyball players during landing. Methods: The neuromuscular recruitment patterns and patellar tendon loading of 20 male and 20 female volleyball players performing a lateral stop-jump block movement were recorded and calculated. Pearson product-moment correlations were conducted to determine whether neuromuscular recruitment patterns were related to the peak patellar tendon force or patellar tendon force loading rate generated at landing. Independent t-tests were applied to a subset of data for 13 males and 13 females matched for jump height to identify any between-sex differences in neuromuscular recruitment patterns. Results: Later onset of rectus femoris (r = 0.312), vastus medialis (r = 0.455), and biceps femoris (r = 0.330) were significantly correlated with a higher patellar tendon force loading rate, although these correlation values were weak. Male volleyball players displayed significantly earlier biceps femoris and semitendinosus onset, and significantly earlier peak semitendinosus activity compared with their female counterparts. Conclusion: Although male and female volleyball players displayed significantly different muscle onset times, these patterns were not strongly related to patellar tendon loading at landing. It is likely that a multitude of factors, including the frequency of patellar tendon loading, more strongly contributes to developing patellar tendinopathy than neuromuscular recruitment patterns in isolation. [ABSTRACT FROM AUTHOR]

Purpose: Fatigue may contribute to knee joint injuries, such as patellar tendinopathy, by increasing joint loading and altering lower limb landing technique, which in turn may increase tissue loading. This study aimed to investigate the effect of lower limb muscle fatigue on the landing technique and patellar tendon loads generated during the horizontal and vertical landing phases of a stop-jump task. It was hypothesized that muscle fatigue would increase patellar tendon loading and alter the landing technique displayed during the horizontal, but not the vertical, landing phase of the stop-jump task. Methods: Sixteen men, recruited from team sports involving repetitive landing, performed repeated trials of a stop-jump task. During each trial, the participants' ground reaction forces and electromyographic activity of seven lower limb muscles were recorded, three-dimensional kinematics measured, and peak patellar tendon force (FPT) calculated. Results: When fatigued, participants generated a significantly lower FPT and FPT loading rate, despite a higher vertical ground reaction force (FV) and FV loading rate, during the horizontal landing phase of the stop-jump task. During the vertical landing phase, participants displayed only minor changes to the kinetics and kinematics of their landing in response to fatigue, although fatigue caused substantial alterations to their lower limb muscle activation patterns during landing. Conclusions: During the horizontal landing phase of the stop-jump task, participants decreased their patellar tendon load when they were fatigued by altering their lower limb landing technique, including a reduced net knee joint extension moment associated with less knee and hip flexion. This decrease in patellar tendon loading when fatigued may be an inherent protective strategy to potentially decrease loading of the tendon during repetitive landing. [ABSTRACT FROM AUTHOR]

The article discusses research investigating the force on the patellar tendon generated when landing from a jump. Researchers examined whether factors associated with the development of patellar tendinopathy, including variables characterizing landing technique, could be used to predict patellar tendon loading in volleyball players when landing from a jump. The study's experimental design and methodology, a discussion of the results, and the researchers' conclusions regarding patellar tendinopathy prevalence in volleyball players and interventions designed to reduce patellar tendon loading are presented.

The article presents a study on the difference between the landing techniques of asymptomatic athletes with patellar tendon ultrasonographic abnormality (PTA) on those with normal patellar tendons. It says that seven athletes who have no previous records of patellar tendon injury and PTA were compared to those who have normal patellar tendons wherein they performed stop-jump task. Results show the difference on the landing strategies between the two groups in which athletes with PTA made the same patellar tendon loading with altered sequencing due to greater knee flexion and extension of their hips. It suggests that the important part in the growth of PTA and patellar tendinopathy may be due to loading patterns.