Experimental muscle pain of the vastus medialis reduces knee joint extensor torque and alters quadriceps muscle contributions as revealed through musculoskeletal modeling

Quantifying voluntary knee strength deficits and muscular contribution to torque in an anterior cruciate ligament-injured adolescent population using a musculoskeletal model

BACKGROUND

Surface electromyography is commonly used to elucidate the effect of anterior cruciate ligament injury on neuromuscular function. For comparisons, electromyography is normalized to a known value, such as peak activation during maximum voluntary isometric contractions. However, a knee injury may compromise one's ability to achieve a true maximal effort. A simple musculoskeletal model may provide insight into injury related strength deficits.

METHODS

Thirty-nine anterior cruciate ligament injured adolescents (14-16 years; 25 females) and 39 matched controls (25 females) completed maximum voluntary isometric knee extension and flexion contractions on an isokinetic dynamometer. A participant-specific musculoskeletal model used normalized electromyography of knee joint muscles to determine a theoretically ideal torque for each contraction type, assuming agonist muscles were fully activated. Strength deficit ratios expressed peak experimental torque relative to theoretically ideal torque. Individual muscle contribution to experimental torque were also computed.

FINDINGS

Injured participants demonstrated significantly lower experimental torque than controls, with percent group mean difference of 17.8 % for knee extension (Injured:2.33 ± 0.89 vs Controls:2.88 ± 0.56 Nm/kg) and 16.7 % for flexion (Injured:1.22 ± 0.44 vs Controls:1.49 ± 0.27 Nm/kg). Group mean differences in strength ratios reduced to 6.3 % for extension (Injured:0.69 ± 0.11 vs Controls:0.74 ± 0.08) and 10.0 % for flexion (Injured:0.56 ± 0.15 vs Controls:0.63 ± 0.12). No between-group differences in muscular contribution to peak experimental extension torque were observed. Injured participants had lower medial gastrocnemius percent contribution to peak experimental flexion torque.

INTERPRETATION

Isometric strength tests may not adequately identify strength deficits in adolescent anterior cruciate injured populations. Simplified modelling frameworks may be more appropriate for evaluating the relationship between neuromuscular control and functional outcomes.

Comparative analysis of isokinetic parameters in individuals with and without chondromalacia patellae

INTRODUCTION

Chondromalacia patella (CMP) is characterizsed by cartilage degeneration, affects young adults, more women (2:1) and is responsible for 75% of knee pain complaints in the active population. The etiology is multifactorial and may be related to extrinsic factors (trauma and burden) and intrinsic factors (patellar malalignment and quadriceps weakness). Isokinetic dynamometry (ID) can aid in the detection of the causal factors of knee pain related to CMP.

OBJECTIVES

To evaluate and compare the parameters of the ID of individuals with and without CMP and correlate them with the clinical aspects of individuals with CMP.

METHODS

This is a retrospective study that analyzed ID of the knee flexors and extensors, performed between 2013 and 2019 in the isokinetic dynamometry sector of the hospital. Six hundred ninety dynamometers tests were included, both sexes, aged between 14 and 59 years, divided into chondromalacia group (342) tests and control group (348) tests. All performed ID in concentric mode for knee extension and flexion, with five maximum repetitions at an angular speed of 60°/s and 180°/s and 20 repetitions at an angular speed of 300°/s, with 30-s intervals between each. After completing the test, the patient points out a number from 0 to 10 on the visual analog scale, regarding the presence and intensity of pain during and after the isokinetic assessment.

RESULTS

The groups had similar distribution from sex (P ​= ​0.071); age (P ​= ​0.99) but were different about pain (P ​< ​0.001). CMP had greater levels of pain. In most of the muscle parameters of the extensors and flexors at 60°/s were lower in the CMP group (P ​< ​0.001).

CONCLUSION

The main predictor of chondromalacia is pain. The greater coefficient of variability and time to reach peak torque on the involved side, the average power and morphology of the extensor curve can also be predictors of chondromalacia.

LEVEL OF EVIDENCE

III.

Evaluating peripheral neuromuscular function with brief movement-evoked pain

Movement-evoked pain is an understudied manifestation of musculoskeletal conditions that contributes to disability, yet little is known about how the neuromuscular system responds to movement-evoked pain. The present study examined whether movement-evoked pain impacts force production, electromyographic (EMG) muscle activity, and the rate of force development (RFD) during submaximal muscle contractions. Fifteen healthy adults (9 males; age = 30.3 ± 10.2 yr, range = 22-59 yr) performed submaximal isometric first finger abduction contractions without pain (baseline) and with movement-evoked pain induced by laser stimulation to the dorsum of the hand. Normalized force (% maximal voluntary contraction) and RFD decreased by 11% (P < 0.001) and 15% (P = 0.003), respectively, with movement-evoked pain, without any change in normalized peak EMG (P = 0.77). Early contractile RFD, force impulse, and corresponding EMG amplitude computed within time segments of 50, 100, 150, and 200 ms relative to the onset of movement were also unaffected by movement-evoked pain (P > 0.05). Our results demonstrate that movement-evoked pain impairs peak characteristics and not early measures of submaximal force production and RFD, without affecting EMG activity (peak and early). Possible explanations for the stability in EMG with reduced force include antagonist coactivation and a reorganization of motoneuronal activation strategy, which is discussed here.NEW & NOTEWORTHY We provide neurophysiological evidence to indicate that peak force and rate of force development are reduced by movement-evoked pain despite a lack of change in EMG and early rapid force development in the first dorsal interosseous muscle. Additional evidence suggests that these findings may coexist with a reorganization in motoneuronal activation strategy.

Effect of soft tissue manipulation of popliteus muscle on quadriceps muscle activity and torque production in athletes with anterior knee pain

Study aim: Popliteus is majorly associated with posterior knee pain; however, this muscle can also have an impact on anterior knee pain. The purpose of this study was to determine the effect of soft tissue manipulation of popliteus muscle on non-traumatic anterior knee pain in athletes; as the relationship between popliteus and Quadriceps muscle has not been studied/explored much.

Materials and methods: In this experimental study, 15 subjects presenting with non-traumatic anterior knee pain were selected. Quadriceps muscle activity, torque production and knee pain were assessed. Followed by a single session of popliteus manipulation all the above parameters were re-assessed immediately and at 24 hours after intervention.

Results: Significant reduction in pain (P < 0.005) at 24 hours was observed. There was a significant increase in muscle activity of Vastus Medialis (P < 0.05) and Vastus Lateralis (P < 0.005) immediately after the intervention but not after 24 hours. No significant change was found in the activity of Rectus femoris and Peak torque of Quadriceps immediately after the intervention and at 24 hours.

Conclusion: Soft tissue manipulation decreased knee pain and improved muscle activity. Therefore, incorporating popliteus manipulation can be effective in treatment of anterior knee pain.