Write me a 1000 word essay reviewing and analyzing the data in this randomized control trial posted next -  The result of this study showed that older adults in the PNF group had decreased pain score, joint proprioception threshold, and external knee adduction moment, whereas increased external knee extension moment after 6-wk stretching compared with those before stretching. Proprioceptive neuromuscular facilitation could be recommended as one of the clinical treatments for KOA to relieve pain, improve proprioception, and balance load distribution between medial and lateral compartments at the knee.
Knee osteoarthritis (KOA), also known as degenerative joint disease, is typically the result of wear and tear and articular cartilage progressive loss 1 and is one of the most common chronic degenerative conditions that adversely affect older adults.2 This condition results in pain, muscle weakness, impaired proprioception, and mechanical malalignment at the knee.1 Pain and muscle weakness results in the progressive shortening of periarticular connective tissue and contracture of the knee, which leads to restricted joint range of motion (ROM).3,4 Impaired proprioception may affect neuromuscular control and joint stability, undermining the ability to accurately control functional movements.5 Therefore, all these impairments could lead to limited walking function, including stair climbing.6 Stair ascending is the first affected task in patients with KOA.2 Compared with level walking, stair ascending demands greater joint ROM and muscle strength to provide sufficient propulsion and better proprioception to perceive spatial position and maintain joint stability.6,7 Compared with level walking, patients with KOA showed greater external knee adduction moment during stair ascending,8 indicating increased force across the medial knee.9 The additional force should be balanced to maintain joint stability in the frontal and sagittal planes to avoid overloading at the knee.10 The external knee flexion/extension moments (eKFM/eKEM) are used to maintain dynamic balance and joint stability.11 However, an increased eKFM leads to great joint reaction force and stress on the patellofemoral joint.12 Therefore, load distribution between medial and lateral compartments at the knee should be balanced by reducing the eKAM, while maintaining the eKFM.
Drugs and injections can reduce pain among patients with KOA but may decrease the protective pain reflex, thus leading to an increased load at the knee and accelerate the deterioration of KOA progress.11,13 Strength training, aerobic exercise, and weight-control training helped relieve pain and strengthen muscles but failed to reduce eKAM and improve proprioception at the knee.14 Toe-in/toe-out gait training decreased eKAM,15 and proprioception training improved joint proprioception.16 However, they failed to relieve other symptoms of the KOA.15,16 Therefore, developing a treatment that could improve as many KOA symptoms as possible is necessary.
Proprioceptive neuromuscular facilitation (PNF) techniques may be beneficial for patients with KOA. Proprioceptive neuromuscular facilitation techniques promote movement around a series of joints in more than one plane to achieve diagonal or spiral movements.17 During PNF stretching, the target muscle is passively stretched to a position, followed by static contraction and then passive movement into a greater position; a shortening contraction of the opposing muscle is used to place the target muscle with additional passive stretch.18 Proprioceptive neuromuscular facilitation techniques can relieve pain 4 and increase the ROM of lower limbs.19 In addition, it may have the potential to enhance the proprioception and reduce the eKAM at the knee. Weng et al.4 confirmed that PNF techniques could remarkably improve pain among patients with KOA than isokinetic exercises. Song et al.20 recently indicated that the passive ROM of patients with KOA substantially increased after PNF stretching. However, the effect of PNF intervention on the active joint ROM during stair ascending among patients with KOA is still unclear. Proprioceptive neuromuscular facilitation stimulates proprioceptors through an integrated pattern to activate and recruit the most prominent muscle fibers for activity participation 17; therefore, it may improve the proprioception. Proprioceptive neuromuscular facilitation technique may decrease eKAM at the knee joint because it includes stretching movements in the frontal plane.3 Improvements in these previously mentioned symptoms are critical for KOA treatment. Therefore, this study aimed to investigate the effects of a 6-wk PNF stretching on pain relief, joint proprioception, active joint ROM, and joint moment improvement among older adults with KOA. The hypothesis is that the participants in the PNF group would experience reduced pain, improved proprioception, increased active joint ROM, and deceased eKAM during stair ascending after undergoing the 6-wk PNF stretching.
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METHODS
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Design
This study was an assessor-blinded, paralleled, and randomized controlled trial. Ethical approval was obtained, and a clinical trial was registered. All participants received written and verbal information and provided written informed consent before participation. This study conforms to all CONsolidated Standards of Reporting Trials guidelines and reports the required information accordingly (see Supplementary Checklist, Supplemental Digital Content 1,
http://links.lww.com/PHM/B413
).
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Participants
All participants were recruited from the local communities by distributing flyers and providing presentations. Seventy-six participants voluntarily participated in this study, see details of the participants elsewhere.20 The inclusion criteria were as follows: 65 yrs or older; diagnosed with unilateral or bilateral KOA according to the clinical criteria of the American College of Rheumatology 21; and a radiographic grade of 1-3 by the Kellgren/Lawrence scale, which means mild to moderate KOA.22 The exclusion criteria were as follows: experienced any neurological or neuromuscular disorder affecting the knee other than the KOA; had a history of any lower extremity joint surgery or fractures in the past 3 mos; reported the presence of chronic, disabling back, hip joint, ankle joint, or foot pain affecting their daily activities; used an assistive walking aid regularly; and assessed as severe cognitive impairment.
Thirty-six participants who met the inclusion criteria were randomly allocated into the PNF or the control groups at a ratio of 1:1 (PNF:control). A randomization sequence was computer generated. Allocation concealment was ensured because allocation information was protected in opaque sealed envelopes and kept by an investigator involved in participant recruitment. The participants in the PNF group received PNF stretching for 6 wks, and those in the control group partook in the health lecture series for 6 wks. The participants were excluded when their attendance rates were less than 80% or had received any treatments or participated in additional exercises. After 6 wks, four participants were excluded because of low attendance in the PNF group, two because of costretching, and three because of low attendance rate in the control group. Final analyses were conducted for the data of 27 participants (n = 14 in the PNF group and n = 13 in the control group). In this study, it was impossible to blind the participants and the therapists about allocation and stretching; only outcome assessors and statisticians were blinded.
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Sample Size Calculation
Sample size estimation was performed using G*Power software (Version 3.1) based on a previous project, which reported that the pain score of patients with KOA decreased from 4.9 +/- 1.4 to 2.7 +/- 1.9 after exercise intervention.4 By setting the significance level to 0.05 and the statistical power to 0.80 in a two-tailed test, the estimated required sample size was 11.
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Stretching
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Proprioceptive Neuromuscular Facilitation Stretching
The participants in the PNF group received PNF stretching for 6 wks,23,24 three sessions per week. Every session of PNF stretching lasted for 1 hr, including 5-min warm-up, 45-min stretching, and 10-min cool down. Proprioceptive neuromuscular facilitation stretching includes diagonal and spiral patterns and four stretching techniques (Table 1, Fig. 1). The details of the PNF stretching were presented elsewhere.20	
Table 1 Table 1Opens a popup window	Figure 1 Figure 1Opens a popup window	Opens a popup window
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Health Lecture Series
All participants in the control group participated in the health lecture series for 6 wks, three sessions per week. One session of health lecture lasted for 1 hr, including knowledge about KOA, awareness of chronic diseases, psychological health education, nutritional meals, scientific exercise, and exchange of experience. The format of the lecture was to watch selected TV programs or read related magazines in the community senior activity room. The participants in the control group were asked to keep their regular, daily lifestyle. The experimenter contacted the participants weekly to confirm they remained eligible for the study.
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Outcome Measures
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Pain Score
The participants were asked to report the pain scores before and after the 6-wk PNF stretching. The pain score refers to the "using stairs pain" subscale of Western Ontario and McMaster Universities Arthritis Index. It was used in this study because the item is closely related to stair activity. The Visual Analog Scale was used to assess the pain score. The Visual Analogue Scale pain score ranged from 0 to 10. Zero represented "no pain" and 10 represented "worst pain possible."4
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Joint Proprioception
Proprioception test devices (Sunny, AP-II, China) were used to detect the proprioception thresholds at the knee and ankle joints. These devices have documented good reliability.25,26 Participants were familiarized with the devices before testing. Then, each participant was seated on an adjustable chair, and their more affected leg was placed on the platform (Fig. 2). The device was adjusted where the hip, knee, and ankle joints were positioned at 90 degrees, while the foot was in contact with the platform. Only half the lower extremity weight was loaded on the platform by using the thigh cuff suspension system to control for unwanted sensory cues that result from contact between the platform and the plantar surface of the foot. During the proprioception test, the participants were blindfolded to remove any visual cues and were listening to music through headphones to eliminate any auditory stimuli from the environment and the instrumentation. All participants were required to concentrate on the testing foot and press the red hand-held switch upon sensing their foot movement and identify the direction of such movement. Dorsiflexion/plantarflexion/inversion/eversion at the ankle and flexion/extension at the knee was randomly performed. At least three successful trials were conducted in each direction. A successful trial was defined as the event when the hand-held switch was pressed as soon as possible after sensing foot movement, and the participant correctly answered the direction of the movement. The experimenter recorded the angular displacement and direction of the movement. The same experimenter measured the proprioception of all participants to guarantee measurements consistency. The average angular displacement of the three successful trials was calculated as the proprioception threshold. The angular displacement of the devices ranged was from 0 to 18 degrees, and a great angular displacement indicates less sensitive proprioceptive function.25	
Figure 2 Figure 2Opens a popup window	Opens a popup window	Opens a popup window
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Joint ROM and Moments During Stair Ascending Test
The details of the staircase are presented elsewhere.20 A force platform (Kistler 9287BAs, Kistler, Switzerland) was embedded in the third step of the staircase. Forty-one retroreflective markers were placed on the bony landmarks according to the Vicon plug-in-gait set.27 Three-dimensional kinematics data were collected by an eight-camera Vicon infrared motion capture system (Vicon, Oxford Metrics, Ltd, United Kingdom) at 100 Hz. The kinematic data were internally synchronized with the force data collected using the force platform at 1000 Hz.
The participants were instructed to ascend the stair in a step-by-step manner using a self-selected pace and then land the foot of the more affected leg on the force plate embedded in the third step. A successful trial was defined as the participant completed the previously mentioned task without pausing on the staircase or losing balance. Three successful trials were collected for data analyses. The participants had a 1-min rest after each trial. The complete gait cycle was defined from the foot of the more affected leg contacted on the third step to the same foot contacted on the fifth step. The single support phase was defined from the foot of the more affected leg contacted on the third step to the same foot left the step. The more affected leg was defined as the leg with a higher Kellgren/Lawrence score, or the one the participant claimed to be more painful when both legs had the same Kellgren/Lawrence score. The average of three successful ascending trials was used for statistical analysis.
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Data Analysis
Pain score, proprioception thresholds, joint ROM, and joint moments were calculated for statistical analyses. The Visual 3D Hybrid Model was used to create the model in Visual-3D software (C-motion, Germantown, MD). The Euler rotations (X-Y-Z) were used to compute joint angles. The hip, knee, and ankle joint center locations were calculated using the marker positions and the anatomic measurements of each participant, respectively. The external moments were the moments created about the joint center from the ground reaction forces and inertial forces.12 Three-dimensional external moments were calculated using inverse dynamics via Visual-3D software and normalized to the individual's body weight and height, the unit of the moment is Newton meter per percent of body weight x height.12 The kinematic and kinetic data were filtered using a fourth-order low-pass Butterworth filter with cutoff frequencies of 6 and 50 Hz.24 Peak angle of lower extremity joints in a complete gait cycle were used as active joint ROM. Peak external moments of lower extremity joints in a single support phase were used for statistical analyses. Positive values represent the moment in hip flexion, knee flexion, and ankle plantarflexion in the sagittal plane, and hip adduction, knee adduction and ankle eversion in the frontal plane.
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Statistical Analyses
Descriptive statistics were presented as mean +/- SDs. The normality of all outcome variables was tested using Shapiro-Wilk tests. Two-way (group x time) analysis of variance with repeated measures was used to compare the dependent variables between the 2 groups before and after the stretching. If a significant interaction effect was detected, the post hoc tests were followed with the Bonferroni adjustments. The significance level was set at [alpha] = 0.05. Partial [eta]2 was used to indicate the effect size of the two-way analysis of variance's main effects and interactions. The thresholds for [eta]2p were as follows: 0.01-0.06 for small, 0.06-0.14 for moderate, and greater than 0.14 for large effect size.28 Cohen d was used to indicate the effect size of post hoc pairwise comparison, and the thresholds for Cohen d were as follows: less than 0.20 for trivial, 0.21-0.50 for small, 0.51-0.80 for medium, and greater than 0.81 for large effect size.29
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RESULTS
All dependent variables were normally distributed, as confirmed by the Shapiro-Wilk tests (P > 0.05). Independent t tests showed no significant differences in age (P = 0.560), height (P = 0.968), weight (P = 0.675), and body mass index (P = 0.523) between the two groups (Table 2).	
Table 2 Table 2Opens a popup window	Opens a popup window	Opens a popup window
A significant group*time interaction was detected in the pain score (P < 0.001, [eta]2p = 0.638) of the more affected leg (Table 3). Post hoc comparisons showed that pain score was significantly decreased in the PNF group at week 7 compared with that at week 0 (P < 0.001, d = 1.47). The pain score was lower in the PNF group compared with those in the control group at week 7 (P < 0.001, d = 2.19).	
Table 3 Table 3Opens a popup window	Opens a popup window	Opens a popup window
In the sagittal plane, significant group*time interactions were observed in proprioception thresholds of the knee flexion (P = 0.006, [eta]2p = 0.267), knee extension (P = 0.016, [eta]2p = 0.212), ankle dorsiflexion (P = 0.007, [eta]2p = 0.259), and plantarflexion (P = 0.020, [eta]2p = 0.197) of the more affected leg. Post hoc comparisons indicated that compared with week 0, proprioception thresholds were significantly decreased in the PNF group in knee flexion (P = 0.002, d = 0.76) and extension (P = 0.049, d = 0.54), and ankle dorsiflexion (P = 0.029, d = 0.80) and plantarflexion (P = 0.011, d = 0.67) at week 7. The knee flexion (P = 0.011, d = 1.05) and extension (P = 0.035, d = 0.86), and ankle dorsiflexion (P = 0.011, d = 1.04) and plantarflexion (P = 0.030, d = 0.87) were lower in the PNF group than those in the control group at week 7.
A significant group*time interaction was detected in the ankle eversion proprioception threshold (P = 0.032, [eta]2p = 0.170) of the more affected leg in the frontal plane. Post hoc comparisons indicated that the ankle eversion proprioception threshold was significantly decreased in the PNF group compared with that at week 0 (P = 0.003, d = 0.84). The ankle eversion proprioception threshold was lower in the PNF group compared with those in the control group at week 7 (P = 0.002, d = 1.33).
No differences were observed in active ROM of the hip, knee, and ankle joints in the sagittal plane in the two groups (Table 4).	
Table 4 Table 4Opens a popup window	Opens a popup window	Opens a popup window
A significant group*time interaction was detected in the external knee extension moment (eKEM) of the more affected leg (P = 0.004, [eta]2p = 0.288; Fig. 3). Post hoc comparisons indicated that the eKEM was significantly increased in the PNF group at week 7 compared with that at week 0 (P = 0.011, d = 0.64). No differences were observed between the PNF and the control groups at week 7.	
Figure 3 Figure 3Opens a popup window	Opens a popup window	Opens a popup window
A significant group*time interaction was detected in the second peak of the eKAM of the more affected leg (P = 0.024, [eta]2p = 0.187; Fig. 4). Post hoc comparisons indicated that the eKAM was significantly decreased in the PNF group compared with that at week 0 (P = 0.026, d = 0.27). No differences were observed between the PNF and the control groups at week 7.	
Figure 4 Figure 4Opens a popup window	Opens a popup window	Opens a popup window
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DISCUSSION
This study investigated the effects of a 6-wk PNF stretching intervention on KOA symptoms during stair ascending. The results partly supported the hypothesis. Proprioceptive neuromuscular facilitation stretching decreased the pain score, knee and ankle joint proprioception thresholds, and eKAM. In addition, an increased eKEM during stair ascending after the stretching was also observed.
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Pain Relief
Pain score was significantly decreased in the PNF group. The pain would influence the stair ascending performance by changing movement patterns in patients with KOA.2 The greater the pain score, the worse the stair ascending performance of the patients with KOA.6 Some exercises were believed to reduce joint pain. Both Bennell et al.30 and Lim et al.31 explored the effects of quadriceps strengthening and neuromuscular exercise on pain among patients with KOA and have confirmed that the interventions effectively reduced pain. Proprioceptive neuromuscular facilitation stretching was also beneficial to reduce pain among patients with KOA. The mechanism of PNF stretching to reduce pain could be explained by the gate control theory.32 During PNF stretching, the afferent inputs from the muscle spindles, joints, tendons, and capsules could inhibit the pain signal transmission at the dorsal gray horn laminae of the spinal cord.19 When performing the hold-relax technique, the antagonist muscles were activated to achieve the isometric contraction of maximum ROM,33 thereby inhibited the transmission of the pain signal.
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Proprioception Improvement
Significant joint proprioception poststretching improvements were observed in most directions, except for ankle inversion. Proprioception is essential for the accurate modulation and activation of muscles to provide adequate neuromuscular control.5 Cross-sectional studies reported that worse knee 34 and ankle 35 proprioception were detected among patients with KOA compared with age-matched older counterparts. The joint mechanoreceptors used to perceive proprioceptive afferent signals degenerate with age. Weaker afferent signals of joint motion and position to the central nervous system led to imprecise motor control.36 Inaccurate movement control during stair walking may cause falls and undesirable consequences.37 Previous studies have reported that kinesthesia and balance exercises could improve knee proprioception and the ability to climb stairs among patients with KOA.16 This study also confirmed that PNF stretching is beneficial to improve joint proprioception. The improvement of proprioception after PNF stretching could be explained by the following mechanisms. First, the spiral and diagonal patterns increased motor neurons' excitability and promoted motor neuron recruitment.17 Subsequently, sensory feedback from the lower limbs might stimulate mechanoreceptors and improve muscle spindle activation.38 Joint mechanoreceptors are essential for detecting the maximum joint ROM, and signals from muscle spindles are crucial for the midrange perception of joint angle.39 When performing PNF stretching, participants continued to perform resistance exercises and maintained isometric contraction at the maximum ROM for a few seconds. This practice could facilitate sensory input. The potential reason for the lack of improvement in ankle inversion proprioception needs to be further studied.
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Joint ROM and Moments During Stair Ascending
This study did not detect any difference in active joint ROM of the lower limbs during stair ascending after PNF stretching. Although limited ROM is one of the most common symptoms of KOA,1 it is unclear whether active joint ROM during functional activities as stair ascending is also affected with KOA. A previous study investigating the same population and intervention on stair descending indicated that passive joint ROM was increased after PNF stretching,20 further confirming the positive effects of PNF stretching on passive ROM rather than on active ROM.
Proprioceptive neuromuscular facilitation stretching led to decreased eKAM, increased eKEM, and maintained eKFM. A decreased eKAM indicates decreased stress on the medial compartment at the knee and a favorable treatment outcome for KOA.9 Derek et al.40 confirmed that wider-step gait training decreased eKAM among patients with KOA, thus decreased medial compartment loading at the knee. Shull et al.41 and Guo et al.15 showed that toe-in or toe-out gait training significantly decreased eKAM at the knee in patients with KOA. It indicates that the frontal movement played an essential role in regulating the load distribution between the medial and lateral compartment at the knee. One of the previous studies reported the eKAM during stair descending among patients with KOA, and no differences were detected after PNF stretching.20 However, the present study showed a significantly reduced eKAM during stair ascending after PNF stretching. This study pointed out that PNF could reduce eKAM in some situations, like stair ascending, as the first affected task in patients with KOA.2
The decreased eKAM may be the benefit of the spiral and diagonal patterns during PNF stretching. Proprioceptive neuromuscular facilitation stretching activated the matched muscle groups on the same kinematic chain and promoted coordinated joint movements in multiple planes,3 especially in the frontal plane. In addition, when PNF spiral and diagonal patterns were performed, the ankle joint needed to be stretched in plantar flexion with inversion or dorsiflexion with eversion, which is similar to toe-in or toe-out gait training. The ankle needs more plantarflexion and inversion in toe-in gait 41 and more dorsiflexion and eversion in toe-out gait.15 The potential mechanism for reducing eKAM could be the change in foot progression angle, which moves the knee joint center medially and the center of pressure laterally, thereby shortened the frontal lever arm.15 Thus, our observations indicated that PNF stretching was adequate to balance loads between the medial and lateral compartments at the knee.
In addition, the outcomes of this study also indicated that after PNF stretching, the eKEM increased while the eKFM maintained unchanged. A decrease in eKAM was often linked to increased eKFM. Increased eKFM could lead to increased compressive forces in the affected knee and hastened KOA progression.12 Proprioceptive neuromuscular facilitation stretching in this project decreased stress on the medial compartment while avoiding the acceleration of KOA progress. One of the previous studies indicated that the eKEM did not change during stair descending after PNF stretching, which was inconsistent with this study.20 Compared with stair descending, stair ascending demands greater lower extremity muscle strength.2 Patients with KOA experience lower limb muscle weakness,42 and the improvement of muscle strength could be observed easier in strength demanding situation,34 like stair ascending. In this study, by enhancing the movement of the antagonist muscles, the eKEM increased. At the same time, the eKFM maintained unchanged, which plays an essential role in maintaining joint stability and preventing knee joint overload.11 Therefore, this study confirmed that PNF stretching could improve the kinetic characteristic of KOA patients during stair ascending.
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Limitations
This study has several limitations. The positive effects of a 6-wk PNF stretching have been demonstrated here. An intervention sustained for a longer time might be even more effective if the dropout rate could be controlled. Furthermore, the observations presented here were constraint by the limited steps of the staircase and only one embedded force platform. The effects of PNF stretching on both legs could be investigated with more steps and more force platforms. In addition, older patients with fourth-grade severe KOA during stair ascending should be examined in the future because only people with Kellgren/Lawrence radiographic grades ranging from 1 to 3 were recruited for this project. Last, future research could add the passive joint ROM measurements to the project, which might provide more insights on the topic.
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CONCLUSIONS
This study confirmed that a 6-wk PNF stretching regime positively affected the symptoms by relieving pain, improving proprioception, and improving joint moments among older adults with KOA. These observations support that PNF should be recommended as one of the clinical treatments for people with KOA.