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Hana Debevec, Douglas R. Pedersen, Aleš Iglic̆ and Matej Daniel

It was shown in several clinical studies that static one-legged stance may be a relevant body position to describe the loads acting at the hip. However, the stress distribution averaged during movement may better describe hip load than hip contact stress distribution in the static body position. Using data on the resultant hip force during walking taken from the measurements of Bergmann (2001), spatial distribution of contact stress over the articular surface was calculated by the HIPSTRESS method and compared with the stress distribution in one-legged stance. It is shown, that the shape of the contact stress distribution during one-legged stance closely resembled the averaged contact stress distribution during the walking cycle (Pearson’s correlation coefficient R 2 = .986; p < .001). This finding presents a link between the hypothesis that the averaged contact stress distribution during a walking cycle is crucial for cartilage development and the results of clinical studies in which the calculated distribution of contact stress in one-legged stance was successfully used to predict the clinical status of the hip.

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Shinya Ogaya, Hisashi Naito, Akira Iwata, Yumi Higuchi, Satoshi Fuchioka and Masao Tanaka

Toe-out angle alternation is a potential tactic for decreasing the knee adduction moment during walking. Published reports have not examined the medial knee contact force during the toe-out gait, although it is a factor affecting knee articular cartilage damage. This study investigated the effects of increased toe-out angle on the medial knee contact force, using musculoskeletal simulation analysis. For normal and toe-out gaits in 18 healthy subjects, the muscle tension forces were simulated based on the joint moments and ground reaction forces with optimization process. The medial knee contact force during stance phase was determined using the sum of the muscle force and joint reaction force components. The first and second peaks of the medial knee contact force were compared between the gaits. The toe-out gait showed a significant decrease in the medial knee contact force at the second peak, compared with the normal gait. In contrast, the medial knee contact forces at the first peak were not significantly different between the gaits. These results suggest that the toe-out gait is beneficial for decreasing the second peak of the medial knee contact force.

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Takeo Nagura, Hideo Matsumoto, Yoshimori Kiriyama, Ajit Chaudhari and Thomas P. Andriacchi

The aim of the study was to estimate the tibiofemoral joint force in deep flexion to consider how the mechanical load affects the knee. We hypothesize that the joint force should not become sufficiently large to damage the joint under normal contact area, but should become deleterious to the joint under the limited contact area. Sixteen healthy knees were analyzed using a motion capture system, a force plate, a surface electromyography, and a knee model, and then tibiofemoral joint contact forces were calculated. Also, a contact stress simulation using the contact areas from the literature was performed. The peak joint contact forces (M ± SD) were 4566 ± 1932 N at 140 degrees in rising from full squat and 4479 ± 1478 N at 90 degrees in rising from kneeling. Under normal contact area, the tibiofemoral contact stresses in deep flexion were less than 5 MPa and did not exceed the stress to damage the cartilage. The contact stress simulation suggests that knee prosthesis having the contact area smaller than 200 mm2 may be problematic since the contact stress in deep flexion would become larger than 21 MPa, and it would lead damage or wear of the polyethylene.

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Lindsey K. Lepley and Riann M. Palmieri-Smith

Clinical Scenario:

Interventions aimed at safely overloading the quadriceps muscle after anterior cruciate ligament (ACL) reconstruction are essential to reducing quadriceps muscle weakness that often persists long after the rehabilitation period. Despite the best efforts of clinicians and researchers to improve ACL rehabilitation techniques, a universally effective intervention to restore preinjury quadriceps strength has yet to be identified. A muscle’s force-producing capacity is most optimal when an external force exceeds that of the muscle while the muscle lengthens. Hence, the potential to improve muscle strength by overloading the tissue is greater with eccentric strengthening than with concentric strengthening. Traditionally, the application of early postoperative high-intensity eccentric resistance training to the ACL-reconstructed limb has been contraindicated, as there is potential for injury to the ACL graft, articular cartilage, or surrounding soft-tissue structures. However, recent evidence suggests that the application of early, progressive, high-force eccentric resistance exercises to the involved limb can be used to safely increase muscle volume and strength in ACL-reconstructed individuals. As a result, eccentric strengthening may be another attractive alternative to traditional concentric strengthening to improve quadriceps strength after ACL reconstruction.

Focused Clinical Question:

In patients who have undergone ACL reconstruction, is there evidence to suggest that eccentric exercise positively affects postoperative quadriceps strength?

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Jay R. Ebert, Anne Smith, Peter K. Edwards and Timothy R. Ackland

Context:

Matrix-induced autologous chondrocyte implantation (MACI) is an established technique for the repair of knee chondral defects. Despite the reported clinical improvement in knee pain and symptoms, little is known on the recovery of knee strength and its return to an appropriate level compared with the unaffected limb.

Objective:

To investigate the progression of isokinetic knee strength and limb symmetry after MACI.

Design:

Prospective cohort.

Setting:

Private functional rehabilitation facility.

Patients:

58 patients treated with MACI for full-thickness cartilage defects to the femoral condyles.

Intervention:

MACI and a standardized rehabilitation protocol.

Main Outcome Measures:

Preoperatively and at 1, 2, and 5 y postsurgery, patients underwent a 3-repetition-maximum straight-leg raise test, as well as assessment of isokinetic knee-flexor and -extensor torque and hamstring:quadriceps (H:Q) ratios. Correlation analysis investigated the association between strength and pain, demographics, defect, and surgery characteristics. Linear-regression analysis estimated differences in strength measures between the operated and nonoperated limbs, as well as Limb Symmetry Indexes (LSI) over time.

Results:

Peak knee-extension torque improved significantly over time for both limbs but was significantly lower on the operated limb preoperatively and at 1, 2, and 5 y. Mean LSIs of 77.0%, 83.0%, and 86.5% were observed at 1, 2, and 5 y, respectively, while 53.4–72.4% of patients demonstrated an LSI ≤ 90% across the postoperative timeline. Peak knee-flexion torque was significantly lower on the operated limb preoperatively and at 1 year. H:Q ratios were significantly higher on the operated limb at all time points.

Conclusions:

While peak knee-flexion and hip-flexor strength were within normal limits, the majority of patients in this study still demonstrated an LSI for peak knee-extensor strength ≤ 90%, even at 5 y. It is unknown how this prolonged knee-extensor deficit may affect long-term graft outcome and risk of reinjury after return to activity.

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Rodrigo R. Bini, Aline C. Tamborindeguy and Carlos B. Mota

Context:

It is not clear how noncyclists control joint power and kinematics in different mechanical setups (saddle height, workload, and pedaling cadence). Joint mechanical work contribution and kinematics analysis could improve our comprehension of the coordinative pattern of noncyclists and provide evidence for bicycle setup to prevent injury.

Objective:

To compare joint mechanical work distribution and kinematics at different saddle heights, workloads, and pedaling cadences.

Design:

Quantitative experimental research based on repeated measures.

Setting:

Research laboratory.

patients:

9 healthy male participants 22 to 36 years old without competitive cycling experience.

Intervention:

Cycling on an ergometer in the following setups: 3 saddle heights (reference, 100% of trochanteric height; high, + 3 cm; and low, − 3 cm), 2 pedaling cadences (40 and 70 rpm), and 3 workloads (0, 5, and 10 N of braking force).

Main Outcome Measures:

Joint kinematics, joint mechanical work, and mechanical work contribution of the joints.

Results:

There was an increased contribution of the ankle joint (P = .04) to the total mechanical work with increasing saddle height (from low to high) and pedaling cadence (from 40 to 70 rpm, P < .01). Knee work contribution increased when saddle height was changed from high to low (P < .01). Ankle-, knee-, and hip-joint kinematics were affected by saddle height changes (P < .01).

Conclusions:

At the high saddle position it could be inferred that the ankle joint compensated for the reduced knee-joint work contribution, which was probably effective for minimizing soft-tissue damage in the knee joint (eg, anterior cruciate ligament and patellofemoral cartilage). The increase in ankle work contribution and changes in joint kinematics associated with changes in pedaling cadence have been suggested to indicate poor pedaling-movement skill.

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Jianwei Duan, Kuan Wang, Tongbo Chang, Lejun Wang, Shengnian Zhang and Wenxin Niu

health maintenance and promotion. For example, moderate contact stress improves the generation of collagen and proteins in the cartilage polysaccharides and extracellular matrix ( Waldman, Spiteri, Grynpas, Pilliar, & Kandel, 2004 ), while prolonged overloading leads to cartilage degradation ( Griffin

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Samuel F. Jazzo, Daniel Scribner, Stephanie Shay and Kyung-Min Kim

Additionally, the type-I cartilage that fills in the lesion after microfracture surgery has different biological and mechanical profiles from hyaline cartilage, thus making it susceptible to degeneration over time. 7 Platelet-rich plasma (PRP) injection may be an adjunctive therapy to further improve treatment

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Susana Meireles, Neil D. Reeves, Richard K. Jones, Colin R. Smith, Darryl G. Thelen and Ilse Jonkers

kinematics and kinetics 4 , 11 , 24 have been explored, which do not provide direct measures of cartilage loading. However, KCF reflect not only the influence of external forces but also the muscle and ligament forces. Computational approaches are noninvasive, do not alter the knee biomechanics, and can be

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Kerry E. Costello, Janie L. Astephen Wilson, William D. Stanish, Nathan Urquhart and Cheryl L. Hubley-Kozey

Progression Gait Literature Study design Study sample Study Progression outcome (S/C) Follow-up, y N (%women) Age, y BMI, kg/m 2 KL Speed, m/s Main features of progression group at baseline Bennell et al 7 S Medial tibial cartilage volume change 1 144 (56%) 64 (8) 28.6 (4.5) 2 1.3 (0.2) • Peak KAM/(bw × ht