Patellar Tendon Loading Research Articles

Ex Vivo Biomechanical Evaluation of the Canine Cranial Cruciate Ligament‐Deficient Stifle with Varying Angles of Stifle Joint Flexion and Axial loads after Tibial Tuberosity Advancement

To evaluate the effect of tibial tuberosity advancement (TTA) on cranial tibial thrust (CrTT), retropatellar force (RPF), patellar tendon load (PTL), and patellar tendon angle determined by the tibial plateau angle (PTA(TPA) ) method or common tangent (PTA(CT) ) method in the canine cranial cruciate ligament (CrCL)-deficient stifle joint. Ex vivo cadaver study. Cadaveric canine hind limbs (n=30). Stifle joints were subjected to 3 differing loading conditions using a constrained limb press model (Group 1: 30% body weight axial load at stifle and talocrural joint angles of 135 ± 5° and 145 ± 5°, respectively; Group 2: 30% body weight axial load at stifle and talocrural angles of 145 ± 5° and 135 ± 5°, respectively; and Group 3: 50% body weight axial load at stifle and talocrural joint angles of 135 ± 5° and 145 ± 5°, respectively). The CrCL was transected in situ under load; sensors allowed direct measurement of CrTT, RPF, and PTL. Lateral radiographic projections were used to assess PTA(TPA) and PTA(CT) . Descriptive statistics were used to report CrTT (by design this force returned to 0-point values, defined as the neutral point of advancement [NPA]). At the NPA, RPF was compared with baseline using a 2-tailed sign test. PTL within groups were compared using a paired t-test; pair-wise comparisons of PTA(TPA) and PTA(CT) were performed using a paired t-test. Comparisons between loading conditions were made with a 1-way ANOVA and Tukey's post hoc test. Equivalence tests were used to test mean PTA(TPA) and PTA(CT) for equivalence to 90°. Significance was set at a P-value of .05. CrTT returned to baseline values, and RPF and PTL at NPA were reduced below baseline values in all specimens in a near linear fashion with TTA. At the NPA, PTA(TPA) >PTA(CT) in 2 of the 3 loading conditions, but insufficient evidence to suggest they differed in the third. Mean PTA(TPA) and PTA(CT) varied between loading conditions. The threshold for each of the groups evaluated, at which the PTA could be significantly different from 90°, was larger for PTA(TPA) than PTA(CT) in all groups, as greater variation was observed with PTA(TPA) versus PTA(CT) . This study further supports the claim that reduction of CrTT occurs after TTA in the CrCL-deficient stifle joint through an alteration of PTA. Additionally, RPF and PTL also decrease after TTA. The PTA(CT) may be a more precise method of determining PTA.

Landing Strategies of Athletes with an Asymptomatic Patellar Tendon Abnormality

Risk factors associated with a clinical presentation of patellar tendinopathy are patellar tendon ultrasonographic abnormality (PTA) and excessive loading. It remains unknown whether characteristics of an athlete's landing technique contribute to this excessive patellar tendon loading. This study investigated whether asymptomatic athletes with and without PTA had different landing strategies and hypothesized that asymptomatic athletes with a PTA would create higher patellar tendon loading and a different lower-limb landing strategy compared with athletes with normal patellar tendons. Seven athletes with no previous history or clinical signs of patellar tendon injury with a PTA were matched to athletes with normal patellar tendons (controls). Participants performed five successful trials of a stop-jump task, which involved a simultaneous two-foot horizontal and then vertical landing. During each trial, the participants' ground reaction forces and lower-limb electromyographic data were recorded, the three-dimensional kinematics measured, and the peak patellar tendon force calculated by dividing the net knee joint moment by the patellar tendon moment arm. Significant between-group differences in landing technique were mostly observed during the horizontal landing phase. Participants with a PTA created similar patellar tendon loading to the controls, but with altered sequencing, by landing with significantly greater knee flexion and extending their hips while the controls flexed their hips as they landed, reflecting a different muscle recruitment order compared with the PTA group. The crucial part in the development of PTA and, in turn, patellar tendinopathy may not be the magnitude of the patellar tendon load but rather the loading patterns. This research provides clinicians with important landing assessment criteria against which to identify athletes at risk of developing patellar tendinopathy.

Do athletes with and without asymptomatic patellar tendon ultrasonographic abnormality differ in their muscle recruitment strategies during landing?

Asymptomatic athletes with patellar tendon ultrasonographic abnormalities (PTA) have been shown to display altered lower limb kinematics and kinetics during landings. Whether these altered biomechanics are accompanied by changes in muscle recruitment strategies and, in turn, increased patellar tendon loading remains unknown. This study aimed to identify whether asymptomatic athletes with and without PTA utilised different lower limb muscle activation patterns during landing. Three-dimensional kinematics, ground reaction forces and electromyographic data for six lower limb muscles were recorded for seven male athletes with an ultrasound-confirmed PTA and seven matched healthy controls while they performed a stop-jump (SJ) movement.

Patellar tendon load in different types of eccentric squats

Patellar tendon load in different types of eccentric squats

Relationship between landing strategy and patellar tendinopathy in volleyball

Objective: The aetiology of patellar tendinopathy (jumper’s knee) remains unclear. To see whether landing strategy might be a risk factor for the development of this injury, this study examined whether...

Patellar tendon load in different types of eccentric squats

Differences in mechanical loading of the patellar tendon have been suggested as a reason for varying effects in rehabilitation of patellar tendinopathy using different eccentric squat exercises and devices. The aim was to characterize the magnitude and pattern of mechanical load at the knee and on the patellar tendon during four types of eccentric squat. Subjects performed squats with a submaximal free weight and with maximal effort in a device for eccentric overloading (Bromsman), on a decline board and horizontal surface. Kinematics was recorded with a motion-capture system, reaction forces with force plates, and electromyography from three leg muscles with surface electrodes. Inverse dynamics was used to calculate knee joint kinetics. Eccentric work, mean and peak patellar tendon force, and angle at peak force were greater (25-30%) for squats on decline board compared to horizontal surface with free weight, but not in Bromsman. Higher knee load forces (60-80%), but not work, were observed with Bromsman than free weight. Angular excursions at the knee and ankle were larger with decline board, particularly with free weight, and smaller in Bromsman than with free weight. Mean electromyography was greater on a decline board for gastrocnemius (13%) and vastus medialis (6%) with free weight, but in Bromsman only for gastrocnemius (7%). The results demonstrated clear differences in the biomechanical loading on the knee during different squat exercises. Quantification of such differences provides information that could be used to explain differences in rehabilitation effects as well as in designing more optimal rehabilitation exercises for patellar tendinopathy.

Decline eccentric squats increases patellar tendon loading compared to standard eccentric squats

Decline eccentric squats increases patellar tendon loading compared to standard eccentric squats

Decline eccentric squats increases patellar tendon loading compared to standard eccentric squats

Recent studies have shown excellent clinical results using eccentric squat training on a 25 degrees decline board to treat patellar tendinopathy. It remains unknown why therapeutic management of patellar tendinopathy using decline eccentric squats offer superior clinical efficacy compared to standard horizontal eccentric squats. This study aimed to compare electromyography activity, patellar tendon strain and joint angle kinematics during standard and decline eccentric squats. Thirteen subjects performed unilateral eccentric squats on flat-and a 25 degrees decline surface. During the squats, electromyography activity was obtained in eight representative muscles. Also, ankle, knee and hip joint goniometry was obtained. Additionally, patellar tendon strain was measured in vivo using ultrasonography as subjects maintained a unilateral isometric 90 degrees knee angle squat position on either flat or 25 degrees decline surface. Patellar tendon strain was significantly greater (P<0.05) during the squat position on the decline surface compared to the standard surface. The stop angles of the ankle and hip joints were significantly smaller during the decline compared to the standard squats (P<0.001, P<0.05). Normalized mean electromyography amplitudes of the knee extensor muscles were significantly greater during the decline compared to the standard squats (P<0.05). Hamstring and calf muscle mean electromyography did not differ, respectively, between standard and decline squats. The use of a 25 degrees decline board increases the load and the strain of the patellar tendon during unilateral eccentric squats. This finding likely explains previous reports of superior clinical efficacy of decline eccentric squats in the rehabilitative management of patellar tendinopathy.

In vivo patellar tendon loading: Comparison between ultrasonic measurement and inverse dynamics

In vivo patellar tendon loading: Comparison between ultrasonic measurement and inverse dynamics

Computational modelling of a total knee prosthetic loaded in a dynamic knee simulator

Dynamic knee simulators attempt to reproduce the estimated forces, moments, and motions of both the patello-femoral and tibio-femoral joints during ambulatory activities. As a continuation of work designed to reproduce desired three-dimensional joint loading and motion on a dynamic knee simulator, the goal of this study was to develop a computational model of a prosthetic knee placed within an existing computational model of a dynamic knee simulator. The resulting model was then used to produce inputs to the controllable axes of the simulator for reproduction of desired knee loading and motion. Previously, a three-dimensional computational model of the simulator was developed and verified using a simplified and instrumented analog knee. The work presented here replaced the simplified and constrained geometries of the analog knee with structures representing a prosthetic knee. Three-dimensional geometries were determined based on digitized surface points of a right total knee replacement. Deformable contacts between the articulating surfaces of the tibio-femoral and patello-femoral joints were then defined and model sensitivities were identified. Predicted results from the computational model were compared to experimental results for force profiles applied at the simulator's controllable axes. Within identified limitations, the model was then used to generate inputs to the simulator to reproduce desired patellar tendon load during a squat and desired out-of-sagittal-plane motion during a squat.

Neovascularisation in chronic painful patellar tendinosis?promising results after sclerosing neovessels outside the tendon challenge the need for surgery

Sclerosing injections targeting neovascularisation have been demonstrated to give promising clinical results in patients with chronic painful Achilles tendinosis. In this study, fifteen elite or recreational athletes (12 men and three women) with the diagnosis patellar tendinosis/Jumper's knee in 15 patellar tendons were included. All the patients had a long duration of pain symptoms (mean = 23 months) from the patellar tendon, and ultra-sonography + colour doppler examination showed structural tendon changes with hypo-echoic areas and a neovascularisation, corresponding to the painful area. The patients were treated with ultrasound and colour doppler-guided injections of the sclerosing substance Polidocanol, targeting the area with neovascularisation. At follow-up (mean = 6 months) after a mean amount of three treatments, there was a good clinical result in 12/15 tendons. The patients were back to their previous (before injury) sport activity level, and the amount of pain recorded on a VAS-scale had decreased significantly (VAS from 81 to 10). Our findings indicate that treatment with sclerosing injections, targeting the area with neovessels in patellar tendinosis, has the potential to cure the pain in the tendons and also allow the patients to go back to full patellar-tendon loading activity.

Interface pressure and shear stress changes with amputee weight loss: case studies from two trans-tibial amputee subjects.

Interface pressures and shear stresses were measured at monthly intervals on two trans-tibial amputee subjects who lost more than 12% of their body weight over the course of the study. For one subject interface pressures and shear stresses during the weight-acceptance phase of gait decreased over the study interval at all 13 sites monitored, while the other subject experienced increased pressures distally but decreased pressures proximally. Subjects' stumps appeared to atrophy over the study interval, increasing distal end and patellar tendon loading, but not increasing interface shear stresses at other locations. Adding socks at the end of the study did not return interface pressures to first session values at all sites. It is expected that local stump shape changes occurred, causing a non-uniform change in interface stress patterns.

Q-angle influences tibiofemoral and patellofemoral kinematics

Numerous surgical procedures have been developed to correct patellar tracking and improve patellofemoral symptoms by altering the Q-angle (the angle between the quadriceps load vector and the patellar tendon load vector). The influence of the Q-angle on knee kinematics has yet to be specifically quantified, however. In vitro knee simulation was performed to relate the Q-angle to tibiofemoral and patellofemoral kinematics. Six cadaver knees were tested by applying simulated hamstrings, quadriceps and hip loads to induce knee flexion. The knees were tested with a normal alignment, after increasing the Q-angle and after decreasing the Q-angle. Increasing the Q-angle significantly shifted the patella laterally from 20° to 60° of knee flexion, tilted the patella medially from 20° to 80° of flexion, and rotated the patella medially from 20° to 50° of flexion. Decreasing the Q-angle significantly tilted the patella laterally at 20° and from 50° to 80° of flexion, rotated the tibia externally from 30° to 60° of flexion, and increased the tibiofemoral varus orientation from 40° to 90° of flexion. The results show that an increase in the Q-angle could lead to lateral patellar dislocation or increased lateral patellofemoral contact pressures. A Q-angle decrease may not shift the patella medially, but could increase the medial tibiofemoral contact pressure by increasing the varus orientation.