Knee flexor strength and rate of torque development deficits in women with patellofemoral pain are related to poor objective function

There is more to the knee joint than just the quadriceps: A systematic review with meta-analysis and evidence gap map of hamstring strength, flexibility, and morphology in individuals with gradual-onset knee disorders

BACKGROUND

Impairments in hamstring strength, flexibility, and morphology have been associated with altered knee biomechanics, pain, and function. Determining the presence of these impairments in individuals with gradual-onset knee disorders is important and may indicate targets for assessment and rehabilitation. This systematic review aimed to synthesize the literature to determine the presence of impairments in hamstring strength, flexibility, and morphology in individuals with gradual-onset knee disorders.

METHODS

Five databases (MEDLINE, Embase, CINAHL, SPORTDiscus, and Web of Science) were searched from inception to September 2022. Only studies comparing hamstring outcomes (e.g., strength, flexibility, and/or morphology) between individuals with gradual-onset knee disorders and their unaffected limbs or pain-free controls were included. Meta-analyses for each knee disorder were performed. Outcome-level certainty was assessed using the Grading of Recommendations Assessment, Development, and Evaluation, and evidence gap maps were created.

RESULTS

Seventy-nine studies across 4 different gradual-onset knee disorders (i.e., knee osteoarthritis (OA), patellofemoral pain (PFP), chondromalacia patellae, and patellar tendinopathy) were included. Individuals with knee OA presented with reduced hamstring strength compared to pain-free controls during isometric (standard mean difference (SMD) = -0.76, 95% confidence interval (95%CI) : -1.32 to -0.21) and concentric contractions (SMD = -0.97, 95%CI : -1.49 to -0.45). Individuals with PFP presented with reduced hamstring strength compared to pain-free controls during isometric (SMD = -0.48, 95%CI : -0.82 to -0.14), concentric (SMD = -1.07, 95%CI : -2.08 to -0.06), and eccentric contractions (SMD = -0.59, 95%CI : -0.97 to -0.21). No differences were observed in individuals with patellar tendinopathy. Individuals with PFP presented with reduced hamstring flexibility when compared to pain-free controls (SMD = -0.76, 95%CI : -1.15 to -0.36). Evidence gap maps identified insufficient evidence for chondromalacia patellae and hamstring morphology across all gradual-onset knee disorders.

CONCLUSION

Our findings suggest that assessing and targeting impairments in hamstring strength and flexibility during rehabilitation may be recommended for individuals with knee OA or PFP.

Lower extremity muscle volume in females with patellofemoral pain and its relationships to hip and knee torque: A cross-sectional study

OBJECTIVES

Compare lower extremity muscle volume in females with patellofemoral pain (PFP) to a cohort of pain-free females and investigate the relationship between thigh and hip muscle volume and torque.

DESIGN

Cross-sectional.

PARTICIPANTS

Twenty-one females, 13 with PFP and 8 pain-free controls.

MAIN OUTCOME MEASURES

We quantified normalized lower extremity muscle volume (cm3/kg*m) via magnetic resonance imaging and isometric hip and thigh torque (Nm/kg) via a multimodal dynamometer.

RESULTS

Versus pain-free individuals, females with PFP had smaller muscle volume of the anterior hip (P < 0.019; d = 0.97-2.42), deep external rotators (P < 0.006; d = 1.0-3.93), hamstrings (P < 0.009; d = 1.09-2.12), rectus femoris (P < 0.001; d = 1.79), and vastus intermedius (P < 0.001; d = 1.88). There was no difference in muscle volume of the gluteus maximus (P = 0.311; d = 0.22), gluteus medius (P = 0.087; d = 0.87), vastus lateralis (P = 0.22; d = 0.39), and vastus medialis (P = 0.47; d = 0.04). Gluteus maximus volume was moderately correlated to hip abduction torque (r = 0.60; P = 0.03). Vasti muscles and semitendinosus volume were moderately correlated to knee extension (r = 0.57-0.69; P < 0.05) and flexion (r = 0.66; P = 0.01) torque, respectively.

CONCLUSION

Females with PFP present with lesser thigh and hip muscle volumes, with variability in volumetric profiles across participants. Lower extremity knee extension and hip abduction strength are moderately associated with the vasti and gluteus maximus muscle volume, respectively.

The Addition of Sprint Interval Training to Field Lacrosse Training Increases Rate of Torque Development and Contractile Impulse in Female High School Field Lacrosse Players

Field lacrosse requires sudden directional changes and rapid acceleration/deceleration. The capacity to perform these skills is dependent on explosive muscle force production. Limited research exists on the potential of sprint interval training (SIT) to impact explosive muscle force production in field lacrosse players. The purpose of this study is to examine SIT, concurrent to field-lacrosse-specific training, on the rate of torque development (RTD), contractile impulse, and muscle function in female high school field lacrosse players (n = 12; 16 ± 1 yrs.). SIT was performed three times per week, concurrent to field-lacrosse-specific training, for 12 weeks. Right lower-limb muscle performance was assessed pre-, mid-, and post-SIT training via isometric and isokinetic concentric knee extensor contractions. Outcomes included RTD (Nm·s^-1), contractile impulse (Nm·s), and peak torque (Nm). RTD for the first 50 ms of contraction improved by 42% by midseason and remained elevated at postseason (p = 0.004, effect size (ES) = -577.3 to 66.5). Contractile impulse demonstrated a training effect across 0-50 ms (42%, p = 0.004, ES = -1.4 to 0.4), 0-100 ms (33%, p = 0.018, ES = 3.1 to 0.9), and 0-200 ms (22%, p = 0.031, ES = -7.8 to 1.6). Isometric (0 rad·s^-1) and concentric (3.1 rad·s^-1) strength increased by 20% (p = 0.002, ES = -60.8 to -20.8) and 9% (p = 0.038, ES = -18.2 to 0.0) from SIT and field-lacrosse-specific training, respectively (p < 0.05). SIT, concurrent to field-lacrosse-specific training, enhanced lower-limb skeletal muscle performance, which may enable greater sport-specific gains.

Quadriceps Neuromuscular Function During and After Exercise-Induced Fatigue in Patients With Patellofemoral Pain

CONTEXT

Exercise-induced fatigue reduces muscle force production and motoneuron pool excitability. However, it is unclear if patients with patellofemoral pain (PFP) experience further loss in quadriceps neuromuscular function due to fatigue during exercise and postexercise.

OBJECTIVE

To observe how quadriceps maximal strength, activation, and force-generating capacity change during and after repetitive bouts of isokinetic knee-extension exercise in patients with PFP.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-two patients with PFP (visual analog scale mean pain severity = 4.2 of 10 cm, mean symptom duration = 38.6 months) and 19 healthy control individuals matched on age and body mass index.

MAIN OUTCOME MEASURE(S)

Quadriceps peak torque (PT), central activation ratio (CAR), and rate of torque development (RTD) were assessed at baseline and immediately after every 5 sets of knee-extension exercise (times 1-5). Participants continued knee-extension exercises until the baseline quadriceps PT dropped below 50% for 3 consecutive contractions.

RESULTS

No group-by-time interaction was observed for quadriceps PT (F5,195 = 1.03, P = .40). However, group-by-time interactions were detected for quadriceps CAR (F5,195 = 2.63, P= .03) and RTD (F5,195 = 3.85, P = .002). Quadriceps CAR (-3.6%, P = .04, Cohen d = 0.53) and RTD (-18.9%, P = .0008, Cohen d = 1.02) decreased between baseline and time 1 in patients with PFP but not in their healthy counterparts (CAR -1.9%, P = .86; RTD -9.8%, P = .22). Quadriceps RTD also decreased between times 4 and 5 in patients with PFP (-24.9%, P = .002, Cohen d = 0.89) but not in the healthy group (-0.9%, P = .99).

CONCLUSIONS

Patients with PFP appeared to experience an additional reduction in quadriceps activation, force-generating capacity, or both during the early and late stages of exercise compared with healthy individuals. Clinicians should be aware of such possible acute changes during exercise and postexercise and use fatigue-resistant rehabilitation programs for patients with PFP.

Patellofemoral pain over time: Protocol for a prospective, longitudinal study investigating physical and non-physical features

Background

This is a protocol for a prospective longitudinal study that aims to investigate: (1) group-by-time changes over a minimum of 15 months follow-up in patellofemoral pain (PFP) symptoms, biomechanical, muscle function, pain processing, and psychological features; (2) the extent to which changes in biomechanical, muscle function, pain processing, and psychological features are associated with changes in self-reported pain, physical performance measures, self-reported function, health-related quality of life (HRQOL), and physical activity level.

Methods

Individuals with PFP (n = 144) and control individuals (n = 85) without PFP were assessed at baseline. Outcomes assessed included: 3D kinematics and kinetics during single leg squat, step-down and single leg hop; maximal torque and rate of torque development of hip abductors and knee extensors/flexors; force steadiness of hip abductors and knee extensors; anterior and lateral trunk endurance; pressure pain thresholds at the center of patella and contralateral shoulder; kinesiophobia (Tampa Scale for Kinesiophobia); pain catastrophizing (Pain Catastrophizing Scale); worst self-reported pain (Visual Analogue Scale); physical performance measures (Single Leg Hop Test and Forward Step-Down Test); self-reported function (Anterior Knee Pain Scale); HRQOL (Medical Outcome Short-Form 36), and physical activity level (Baecke's Questionnaire). Follow-up assessments will be identical to the baseline and will be performed after a minimum of 15 months. Generalized linear mixed model (GLMM) will be used to investigate group-by-time differences. Linear regression models will be used to determine the extent to which changes in biomechanical, muscle function, pain processing, and psychological features are associated with changes in self-reported pain, physical performance measures, self-reported function, HRQOL, and physical activity level.

Discussion

Physical and non-physical features have been previously associated with PFP. However, the present study will be the first to investigate their integrated evolution as part of the natural history of PFP and its progression. In doing so, we will be able to determine their behavior in the long-term, as well as how they prospectively associate with each other and with clinical outcomes. Ultimately, this will provide a greater understanding of predictors of long-term outcome and possible targets for interventions.

Relationship between vastus medialis Hoffmann reflex excitability and knee extension biomechanics during different tasks in women with patellofemoral pain

BACKGROUND

Impaired knee extension biomechanics and spinal excitability have been reported in women with patellofemoral pain, but their relationship has not been explored. A significant relationship between them could indicate the need for investigating the potential benefits of disinhibitory interventions for women with patellofemoral pain. Thus, this study aimed to investigate the relationship between vastus medialis Hoffmann reflex and (1) maximal isometric, concentric and eccentric knee extensor strength and rate of torque development; (2) knee extensor torque steadiness; and (3) knee extensor moment during functional tasks; in women with patellofemoral pain.

METHODS

Spinal excitability of twenty-four participants was assessed by the amplitude of maximal vastus medialis Hoffmann reflex. Knee extensor strength, rate of torque development and torque steadiness were assessed using an isokinetic dynamometer. Knee extensor moment during step-down and stair descent tasks were obtained using a three-dimensional motion analysis system.

FINDINGS

A moderate negative relationship was found between vastus medialis Hoffmann reflex and knee extensor torque steadiness (r = -0.35; p = 0.05); whereas a moderate positive relationship was found with maximal isometric knee extensor strength (r = 0.37; p = 0.044). No significant relationships were found between vastus medialis Hoffmann reflex and the other variables.

INTERPRETATION

Our findings provide insight on the relationship between spinal excitability and neuromuscular control of maximal and submaximal isometric torque production in women with patellofemoral pain. Conversely, spinal excitability does not seem to be related with dynamic torques and moments of the knee extensors in women with patellofemoral pain.

Local neuromuscular characteristics associated with patellofemoral pain: A systematic review and meta-analysis

BACKGROUND

Local neuromuscular deficits have been reported in people with patellofemoral pain. We synthesised the neuromuscular characteristics associated with patellofemoral pain to help identify interventional targets and potential mechanisms.

METHODS

Five databases were searched for local neuromuscular characteristics in case-control studies. Electromyography, flexibility, muscle performance and cross-sectional area data were derived from functional or isolated task investigations and synthesised accordingly. An evidence gap map was constructed.

FINDINGS

Sixty-seven studies were included. In functional tasks, electromyographic investigations showed moderate evidence of small effect for vastus medialis onset-delays relative to vastus lateralis (0.44 [0.03, 0.85]) during stepping/stair negotiation tasks, and higher biceps femoris mean excitation amplitudes (0.55 [0.06, 1.04]) in single-leg triple-hop test. In isolated tasks, we found moderate evidence of medium effect for lower Hoffman-reflex amplitude of vastus medialis (-1.12 [-1.56, -0.67]). Muscle performance investigations showed; strong evidence with medium and small effects for lower extensors concentric (-0.61 [-0.81, -0.40]) and eccentric (-0.56 [-0.79, -0.33]) strength, and moderate evidence of medium effect of lower isometric (-0.64 [-0.87, -0.41]) strength, moderate evidence with small effect for rate of force development to 30% (-0.55[-0.89, -0.21]), 60% (-0.57[-0.90, -0.25]) and medium effect to 90% (-0.76[-1.43, -0.10]) of maximum voluntary contraction, and small effect for lower flexors concentric strength (-0.46 [-0.74, -0.19]) and extensors total work (-0.48 [-0.90, -0.07]). Flexibility investigations showed tighter hamstrings (-0.57 [-0.99, -0.14]).

INTERPRETATION

Differences within quadriceps and hamstrings motor-control, hamstrings tightness, and quadriceps and hamstrings weakness are associated with patellofemoral pain, and can be used to guide investigations of treatment effects.

Trunk muscle endurance in individuals with and without patellofemoral pain: Sex differences and correlations with performance tests

OBJECTIVES

To compare trunk muscle endurance among females and males with and without patellofemoral pain (PFP), and to investigate the correlations between trunk muscle endurance and performance of the single leg hop test (SLHT) and forward step-down test (FSDT).

DESIGN

Cross-sectional.

SETTING

Laboratory-based study.

PARTICIPANTS

110 females and 38 males with PFP, 61 females and 31males without PFP.

MAIN OUTCOME MEASURES

Anterior and lateral trunk muscle endurance were assessed with the prone and bilateral side-bridge tests, respectively. Performance during the SLHT and FSDT was also assessed.

RESULTS

Lower anterior and lateral trunk muscle endurance were identified in females (p < .001; d = -0.74 to -0.86), but not in males (p ≥ .806; d = -0.04 to 0.05) with PFP as compared to sex-matched controls. Moderate to large, positive correlations between anterior and lateral trunk muscle endurance with performance in the SLHT and FSDT were identified in females (r = .27 to .50; p < .004) and males (r = 0.27 to 0.59; p < .031) with PFP and females without PFP (r = 0.26 to 0.40; p < .044).

CONCLUSION

Our findings highlight that assessing trunk muscle endurance is advised in females with PFP. Trunk muscle endurance of individuals with PFP may have a role in the performance of hopping and stepping down tasks.

How effective is an evidence-based exercise intervention in individuals with patellofemoral pain?

OBJECTIVES

Guidelines for a comprehensive rehabilitation programme for patellofemoral pain (PFP) have been developed by international experts. The aim of this study was to analyse the effect of such a rehabilitative exercise programme on pain, function, kinesiophobia, running biomechanics, quadriceps strength and quadriceps muscle inhibition in individuals with PFP.

DESIGN

Observational study.

SETTING

Clinical environment.

PARTICIPANTS

Twenty-seven participants with PFP.

MAIN OUTCOME MEASURES

Symptoms [numeric pain rating scale (NPRS)and the pain subscale of the Knee Injury and Osteoarthritis Outcome Score (KOOS)], function measured by using the KUJALA scale and KOOS, kinesiophobia measured by using the Tampa scale, three-dimensional biomechanical running data, quadriceps isometric, concentric and eccentric strength and arthrogenic muscle inhibition (AMI) were acquired before and after the six-week exercise programme.

RESULTS

Although pain did not significantly improve all patients were pain-free after the six-week exercise programme (NPRS: p = 0.074). Function, kinesiophobia and quadriceps AMI improved significantly after the six-week exercise programme (KUJALA: p = 0.001, KOOS: p = 0.0001, Tampa: p = 0.017, AMI: p = 0.018). Running biomechanics during stance phase did not change after the exercise intervention. Quadriceps strength was not different after the six-week exercise programme (isometric: p = 0.992, concentric: p = 0.075, eccentric: p = 0.351).

CONCLUSION

The results of this study demonstrate that the current exercise recommendations can improve function and kinesiophobia and reduce pain and AMI in individuals with PFP. There is a need for reconsideration of the current exercise guidelines in stronger individuals with PFP.

Knee flexor strength, rate of torque development and flexibility in women and men with patellofemoral pain: Relationship with pain and the performance in the single leg bridge test

OBJECTIVES

To investigate the relationship between: (1) knee flexor strength, rate of torque development (RTD), and flexibility with pain level; (2) knee flexor strength and RTD with the performance in the single leg bridge test (SLBT) in women and men with patellofemoral pain (PFP).

DESIGN

Cross-sectional.

SETTING

Laboratory-based study.

PARTICIPANTS

39 women and 36 men with PFP.

MAIN OUTCOME MEASURES

Knee flexor strength, RTD, and flexibility; performance in the SLBT, current, and worst pain level.

RESULTS

Moderate to strong significant negative relationships were identified between the current pain level with knee flexor strength (r = -0.57 to -0.34) and flexibility (r = -0.44 to -0.35); and between knee flexor strength and RTD with the performance in the SLBT (r = 0.34 to 0.57) in women and men with PFP. Knee flexor RTD was not related to any pain level and no significant relationships were identified between the worst pain level with knee flexor strength and flexibility in women and men with PFP.

CONCLUSIONS

Our results support the potential value of assessing knee flexor strength and flexibility in women and men with PFP. The SLBT may be a useful tool to assess knee flexor muscle capacity in individuals with PFP in a clinical setting.