关节力学负荷与骨关节炎的发生发展：太极拳在治疗康复中的应用

李静先

关节力学负荷与骨关节炎的发生发展：太极拳在治疗康复中的应用

李静先

编者按：

随着经济的发展和社会进步，运动生物力学以其较高的定量水平及其与现代先进科学技术紧密结合的特点，在竞技体育和全民健身中得到日益广泛的应用。目前，国际运动生物力学的发展除了对运动技术优化一直保持着高度的关注之外，从上世纪末开始，有关损伤防治的生物力学、动作控制与发展的神经肌肉控制过程和机理先后成为研究热点。天津体育学院长期致力于运动生物力学（时称人体机动学）的研究与学科建设工作，较早招收了运动生物力学的研究生，使其成为国内运动生物力学教学和研究的重镇。本专栏在纪念刘世藩先生诞辰100周年活动时，对来自美国、加拿大和国内的专家学者就相关领域的热点问题进行了约稿。专栏论文以实例介绍了康复生物力学、运动技术生物力学、流体力学、动态系统理论和应用，既展示了天津体育学院运动生物力学学科的学术传承及其影响力，又启示了动作技能的形成和发展的神经-肌肉力学原理和损伤预防和康复的生物力学机制这两个值得关注的发展方向。 ——本刊编辑部

下肢骨关节炎是导致残疾的最常见疾病之一，也是对患者及家庭、医疗系统及社会带来最大影响的运动系统的主要疾患。骨关节炎是包括关节力学变化（如下肢骨骼力学轴线排列异常，关节负荷分布异常，活动过程中关节力矩异常）、韧带走向异常、软骨退化或软骨成分降解和肌肉神经控制功能异常等复合因素引起的全关节疾患。尽管其确切的发病机制仍不明了，关节生物力学在其发生和病程发展中的作用已为大量的前瞻性研究和持续数10年之久的长期追踪研究所证实。综述骨关节炎生物力学及病理机制的研究状况，生物力学干预在骨关节炎治疗康复中的应用，以及太极拳的生物力学特征及其在骨关节炎治疗康复中应用的最新研究进展。基于目前上述领域和太极拳生物力学特征的科学研究状况分析，以及美国风湿病学会在2012年发表的最新骨关节炎非手术和药物治疗指引中将太极拳列为膝骨关节炎运动干预方式之一所带来的国际影响，为了深入探索太极拳在下肢骨关节炎治疗康复效果的机制，以及发展有科学研究事实支持的太极拳运动干预康复方案，未来此领域的研究需要致力于研究骨关节炎患者身体活动时的关节生物力学变化，典型太极拳运动的生物力学特征，以及骨关节炎患者在太极拳运动干预过程中下肢关节力学的变化特征。

骨关节炎；关节力学；太极拳；步态；关节力矩

1 Introduction

Osteoarthritis(OA)is a common cause of disability worldwide.An epidemiological study[1]showed that approximately15%of the world’s population suffers from OA.According to a World Health Organization report(2007),80%of OA patients older than 60 years suffer from limited mobility,and 25%cannot perform major daily activities[2].OA affects one out of eight Canadians(13%of the national population)and is a major cause of long-term disability in the Canadian labor force[3].In China,the prevalence rates of radiographic knee OA in certain regions are 42.8%in women and 20%in men aged 60 years and above[4-6].In general,OA affects weight-bearing joints,such as the hip and knee;the continuous increase in OA prevalence has affected all levels of society[7].According to the Canada Arthritis Network[3],more than 10 million Canadians per generation(one out of four individuals)are expected to suffer from either OA or rheumatoid arthritis.These conditions lead to social,psychological,and economical burdens to patients and incur significant financial consequences.The prevalence of these diseases is expected to increase further because of the increasing incidence of obesity as well as the aging population[8].

OA is a disease of the entire joint;its multifactorial etiology includes increased mechanical stress,ligament derangement,cartilage degradation,subchondral bone change,and muscular impairment.Secondary synovial inflammation also contributes to OA development[9].Although the exact cause of OA remains unknown,evidence indicates that altered loading mechanisms and biomechanics as well as increased mechanical forces on weight-bearing joints significantly contribute to OA onset and progression[10-11].These loads may be acute,such as in post-traumatic OA.However,the effects of altered or abnormal loads on joint structures and functions manifest only after several years or decades.Biomechanical interventions,such as gait training,shoes,and orthotics,have further demonstrated the biomechanical nature of OA.These interventions may delay the structural progression of OA and palliate the associated pain.

Exercise is recommended for conservative OA management,as stated in general clinical guidelines[12-13].In particular,the American College of Rheumatology(ACR)has recently recommended tai chi as a form of exercise therapy for knee OA[14].However,most of the recommended exercises focus only on pain relief and joint function maintenance and rarely considers the importance of joint loading in OA progression and neuromuscular control.As a result,exercise interventions have no significant effect on OA progression.Thus,conservative treatment and rehabilitation have become integral in the development of effective exercise intervention programs for lower-limb OA.

This review focuses on the biomechanics and pathomechanisms of OAas well as on the current views on the disease,the mechanical nature of its onset and progression,and the biomechanical interventions for its treatment and rehabilitation.Furthermore,research on tai chi biomechanics and on its effects on lower-limb OA management is introduced.Research gaps and the future direction of research in tai chi and lower-limb OA biomechanics are also provided.This review focused on the lower extremities,which include the hip,knee,and ankle,because these joints are highly weight-bearing and are thus the most commonly affected by OA[1].

2 Biomechanics and Pathomechanics of OA

2.1 Lower-limb malalignment and OA

The mechanical axis or alignment of the lower extremity is defined by drawing a line from the center of the femoral head to the center of the ankle joint.The line medially passes near the center of the tibial head.Therefore,the medial compartment of the knee sustains 60%to 70%of the load[15-16].The uneven load distribution on the knee is consistent with the high incidence of medial compartment knee OA.Varus-and valgus-aligned knees are the most common malalignments of the lower extremity.A varus-aligned knee is described as“bow-legged,”whereas a valgus-aligned knee is described as“knocked-knee.”The valgus and varus alignments affect the load distribution across the articular joint surface[17]and reduce the load bearing areas.Mechanically,the entire lower extremity acts as an integrated kinetic chain.Therefore,bone alignment may affect the loading patterns at one level and have a profound impact on the other levels.

2.2 Biomechanical loading and lower-limb OA

Studies have shown that altered loading mechanisms and weight-bearing joint biomechanics significantly contribute to OA onset and progression.One theory states that repetitive mechanical loading accelerates the“wear and tear”of the joints[18].This theory is supported by research on obese people and on a number of occupational workers who must perform repetitive knee-bending movements or bear heavy weights.Obesity exerts a high mechanical load on the joint and is associated with incidental OA and OA progression[19].Strong evidence suggests a major link between obesity and increased risks of knee and hip OA[20].In an 11-year,longitudinal cohort prospective study in Sweden[20],researchers found relationships between different body-mass measures and incidence of severe knee and hip OA,which is defined as OA-induced arthroplasty of the knee or hip.The body mass index(BMI),waist circumference,waist-to-hip ratio,weight,and percentage of body fat of 11 026 men and 16 934 women from the general population were measured at the baseline.The incidence of OA across 11 years was monitored through the discharge register of a Swedish hospital.The study provided strong evidence of the association between obesity and knee and hip OA incidences.All overweight measures were associated with knee OA incidence,and the strongest relative risk gradient was observed forBMI.Smaller but still significant differences were found in the hip OA incidences of normal-weight and obese subjects.The strong associations between obesity,mechanical loading,and increased risk of knee and hip OAin both men and women were confirmed by the study.

The“wear and tear”theory was supported by the study on occupational joint use and OAonset by Felson et al[21].The group longitudinally assessed the association between occupational joint use and OA in a large population with multiple occupations.For over 40 years,the occupational status and knee OA of the subjects were assessed using weight-bearing knee radiography when the subjects reached a mean age of 73 years.The job of each subject was characterized in terms of its level of physical demand and its association with knee bending.The study found that men whose jobs required knee bending and involved at least moderate physical demands had higher risks of developing radiographic knee OA than men whose jobs required neither of the activities(43.4%vs.26.8%).The rates of severe radiographic OA(osteophytes and joint-space narrowing)and bilateral radiographic OA also significantly increased in these men.These results indicate that for men,occupations that combine knee bending and physical demands may be a major cause of OA.A large number of studies that focused on the relationship between mechanical load and OA proposed partial OAdevelopment mechanisms.

2.3 Altered mechanical loading and lower-limb OA

Longitudinal studies have provided complete evidence of the causal relationship between aberrant mechanical loading,OA onset,and OA progression.Shakoor et al[22]investigated the onset and progression of OA in approximately 6 000 arthroplasties.In the study,the long-term consequences of single-joint,lower-extremity arthritis were evaluated for more than a decade using a longitudinal database of total joint arthroplasties.OA patients undergoing unilateral hip replacement and who were predicted to suffer from progressive OA in their knees had a 71%chance of progression from the knee contralateral to the replaced hip compared with the ipsilateral knee[22].By contrast,contralateral knee(54%)and the ipsilateral knee(46%)were randomly involved in control individuals with rheumatoid arthritis that was not thought to be mechanically mediated.A prospective cohort study involving 3 026 participants aged 50 years to 79 years further confirmed the effect of aberrant mechanical loading on OA onset[23].In this study,the associations between leg-length inequalities(which result in unequal loading on the knee joints)and prevalent,incident,and progressive knee OA were determined.After a follow-up period of 30 months,participants with leg-length inequalities greater than 1 cm exhibited increased rates of prevalent and progressive radiographic OA in the shorter leg as well as an increased risk of incident symptomatic OAin both legs.

2.4 Biomechanical intervention for OA management

The mechanisms of OA onset and development remain unclear.However,OAis believed to be a multifactorial disease that involves anatomical,biomechanical,and metabolic processes and is determined by age and genetic factors.The previously discussed studies have demonstrated the importance of the mechanical component in OA progression.Biomechanical analyses,such as stair and ramp walking,are non-invasive and reproducible methods of assessing the dynamic loading on joints during motion[24].During gait studies,the walking motion is recorded by cameras,and the ground reaction forces are measured by force plates.Joint loads are then calculated by analyzing the recorded motion and ground reaction-forced.External moments or rotational torques of the joints are used to predict internal joint loads[25-26].Results of the gait analysis in OApatients showed that knee adduction moment(AddM)is a standard surrogate marker of knee loading because of its association with radiographic severity[27],pain[28-29],meniscus pathology and bone size[30],surgical outcomes[31],and disease progression[32].

The effects of mechanical loads on OA onset have been investigated,and biomechanically active interventions,which aim to correct abnormal joint loading patterns or reduce joint loading,have been applied in the management of lower-limb OA.Based on numerous experimental studies and clinical trials,the ACR(2012)recommended several biomechanically active interventions as nonpharmacologic therapies for hip and knee OA.Walking aids,including walking sticks,canes,and walkers,are the most widely accepted,mechanically active modalities.Canes have been used since antiquity and have been demonstrated to allow effective unloading of the knees[33].Gait training,which includes reducing gait speed[34]and increasing the“toe out”angle while walking(during which the feet are externally rotated)[35-36],has also been used in OA rehabilitation.A“medial thrust”gait was also found to reduce knee loading by approximately 15%[37].Meanwhile,orthotic shoe insertion and orthotic shoes have been suggested to relieve OA symptoms.Lateral wedge orthotics have been recommended for knee load reduction[38].The biomechanical basis of these applications relies on forcing the foot into a more medial center of pressure to change the tibiocalcaneal angle and reduce the stresses on the medial knee[39].The degree of wedge angle is directly related to the magnitude of unloading achieved at the knee[38].However,large wedge angles cause foot and ankle discomfort;a 7°wedge is generally accepted as the maximum angle for prolonged use[40].

3 Application of tai chi for OA management

OA patients consistently experience pain,decreased range of motion(ROM),joint stiffness,muscle weakness[41],and somatosen-sory deficits[42-43]that are associated with the structural progression of the disease[44].Exercise has been recommended as an effective OA management therapy[12,14,45-46].However,physical activity and exercise for patients with hip or knee OA may be challenging because of the diseased joint.Moreover,the onset and progress of hip and knee OA are partly mediated by aberrant mechanical loads on the joints[47-48].Therefore,a specific mode of exercise intervention for patients with hip or knee OA is critical.Traditional exercises for OA patients have mainly focused on pain relief and joint function improvement;aberrant joint mechanics has rarely been considered in OAmanagement.

Tai chi has been recommended for the management of knee OAby theACR[14,49-50]based on published results.This form of exercise relieves pain and improves the joint ROM of OA patients[14].Studies on tai chi biomechanics and the beneficial effects of this exercise on physical capacity have shown that tai chi can fulfill the exercise requirement of OA patients by improving muscle strength,endurance,neuromuscular control,and flexibility and by relieving joint pain and stiffness.Cross-sectional studies have shown that regular tai chi practitioners have improved balance,proprioceptive function,muscle strength and endurance,and muscular reaction of the lower extremities compared with their sedentary counterparts or regular jogging and walking enthusiasts[51-54].Several tai chi intervention studies also showed significant improvements in the knee extension and flexion strengths in elderly people who practice tai chi for 3 and 12 months[46].The results of our tai chi biomechanics studies showed that regular tai chi practice can improve muscle strength and endurance and promote proprioceptive and neuromuscular control functions[52-56].Our findings showed that regular tai chi provides the same benefits as those gained from walking and swimming;however,this form of exercise has a lower impact and allows neuromuscular control training[57-58].

The effects of tai chi on knee OA have been investigated in the past two decades.Several research groups examined the effects of tai chi intervention on pain relief,ROM improvement,muscle strength,and flexibility.Their results showed that tai chi alleviates pain and stiffness and improves the ROM,muscle strength,balance,walking endurance,and quality of life of OA patients[49-50,59-65].A highly controlled tai chi study by Wang et al.(2011)focused on knee OA patients.The group conducted a single-blind,randomized controlled trial on 40 individuals with symptomatic knee OA.Tai chi intervention lasted for 60 minutes and was conducted twice a week for 12 weeks.Attention control(wellness education and stretching)served as the control.Ten modified forms from classical,Yang-style tai chi were used in the intervention program,and measurements were conducted before and after tai chi intervention(12,24,and 48 weeks).The measurements included the Western Ontario and McMaster Universities OA(WOMAC)pain score at 12 weeks as well as the WOMAC function,patient and physician global assessments,timed chair stand tests,depression index,self-efficacy scale,and quality of life assessments.The results showed that tai chi reduces pain,alleviates depression,and improves the physical function,self-efficacy,and health-related quality of life of knee OA patients.This study provided strong scientific evidence for the use of tai chi in knee OA management and became the foundation for theACR recommendation.

A number of questions were raised in the published studies on tai chi and OA.First,the selected tai chi movements varied from the 12-movement Sun style[60-62]and 10-movement Yang style to the 24-movement simplified tai chi[49，63].In addition,the intervention duration ranged from a few weeks to 12 weeks,followed by a six-month follow-up period[59].The differences in the biomechanics of the tai chi styles and movements as well as in the intervention durations may have affected the study outcomes.Furthermore,the biomechanics of the applied tai chi movements have not been fully studied.As a result,the effects of tai chi on joint biomechanics remain unclear.The studies also focused on knee ROM,knee pain,joint stiffness,walking speed,and stride length but did not investigate the three-dimensional(3D)joint biomechanics of OA patients.Published studies[66]have suggested that gait assessment without a complete 3D analysis provides limited information on the level of joint impairments and limits the development of rehabilitation strategies.Therefore,a 3D biomechanical analysis is necessary to determine the mechanism by which the kinematics and kinetics of the joints change during intervention and to provide a quantitative analysis of the intervention effects.The unknown factors limit the understanding of the mechanisms of tai chi application in OA management and may affect the outcome of the intervention.In addition,the research results were obtained mainly from knee OA patients and are thus not applicable for hip and ankle OA cases.Therefore,to determine the efficacy of tai chi intervention programs for OA patients,the biomechanical characteristics of tai chi movements that can be used for OA rehabilitation must be investigated to determine the effects of tai chi intervention on the joint biomechanics of the lower limbs of hip,knee,and ankle OApatients.

Current understanding of the biomechanics of tai chi movement is limited.A small number of 3D biomechanical analyses of tai chi movements,particularly in terms of joint biomechanics,have been conducted.To the author’s knowledge,one publication reported the joint moment and loading force of the lower extremities of elderly and young people during normal walking and tai chi stepping[67].One study examined the ground reaction force during tai chi stepping[58],and a few studies investigated the plantar pressure distribution during tai chi practice[68-69].The highest knee-joint reaction forces during tai chi stepping is equivalent to 1.2 times the body weight(BW)[58];this force is significantly lower than the joint reaction force while walking(3×BW)[70].Our group recently analyzed the 3D kinematics and kinetic features of the hip,knee,and ankle during two typical tai chi movements,namely,“Repulse Monkey”and“Wave-hand in Cloud.”A group of experienced male tai chi practitioners(n=15)with at least four years of regular tai chi practice and training participated in the study.The tai chi movements and walking trials were recorded using a motion analysis system and force plats.The results showed that compared with walking,“Repulse Monkey”exerts a significantly weaker vertical ground reaction force,which indicates low impact on the lower limb joints during the two tai chi movements.Although the peak joint moments of force during knee abduction and adduction were larger than those during walking,the joint moment impulses during these processes were significantly smaller.Similar results for the joint moments of force of the lower extremities were found during the“Wave-hand in Cloud”movement.The changes in the joint moment of the lower extremity indicate that the two tai chi movements are suitable for mild to moderate OA patients because of the low loading rate and acceptable load magnitude.An appropriate mechanical load is required by musculoskeletal tissues to maintain physiological joint homeostasis.Tai chi movement characteristics,such as lower-limb ROM,center of gravity,and joint loading,significantly vary with the movement type,and the joint biomechanics of one tai chi movement cannot be applied to other tai chi movements.Thus,a clear understanding of joint and tai chi biomechanics must be obtained to promote OA rehabilitation and develop innovative tai chi rehabilitation programs.The underlying biomechanical principles may be used to understand the mechanical loading,muscle activity,and ROM of the lower limbs of OA patients and may provide a scientific basis for the development of tai chi regimens that are specific for OArehabilitation.

4 Summary

OA is considered a disease of the entire joint,and the role of biomechanics in OA onset and development has been well-documented.Tai chi is recommended for the nonpharmacological management of knee OA.However,additional biomechanical studies on tai chi biomechanics and joint biomechanics of OA patients must be conducted to obtain a clearer understanding of the mechanisms of tai chi application in OA management.Research papers in tai chi and OA management studies published from 1996 to 2013 in the Medline Ovid database(using“tai chi”and“OA”as keywords)showed that approximately two thirds of these articles are original studies.This indicates the increased recognition of the potential application of tai chi in OA management.However,this review revealed several research limitations that must be addressed.First,knowledge on the joint biomechanics of OA patients is limited because of insufficient biomechanical studies on OA patients.For example,the joint loading in OA patients during daily activities remains poorly understood.Furthermore understanding to joint biomechanics during performing tai chi movement is a little.A clear understanding to joint and tai chi biomechanics must be obtained in order to improve OA management and develop innovative tai chi rehabilitation programs.And finally the effects of tai chi intervention on hip OA and ankle OA are unknown.The underlying biomechanical principles may be used to understand the mechanical loading,muscle activity,and ROM of the lower limbs of OA patients during their daily living activity and during performing tai chi.Tai chi and other exercise intervention programs for OA management should be developed based on biomechanical research evidence bases.Biomechanical analysis can then be used to investigate the efficacy of these tai chi programs in the OApatients and improving their long-term mobility.

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Joint Mechanical Load and Osteoarthritis：Application of Tai Chi for Treatment and Rehabilitation

Li Jingxian
（1.School of Human Kinetics，University of Ottawa，Ottawa，Canada125 University Street，Ottawa，Ontario，K1N 6N5，Canada；2.Insti⁃tute of Sports Sciences，Shanghai University of Sport，Shanghai 200438，China）

Osteoarthritis（OA）is a common cause of disability worldwide.It leads to social，psychological，and economical burdens to patients and incur sig⁃nificant financial consequences.OA is a disease of the entire joint；its multifactorial etiology includes increased mechanical stress，ligament derangement，cartilage degradation，subchondral bone change，and muscular impairment.Although the exact cause of OA remains unknown，evidence indicates that al⁃tered loading mechanisms and increased mechanical forces on weight-bearing joints significantly contribute to OA onset and progression.This article reviewed the biomechanics and pathomechanisms of OA，the mechanical nature of OA onset and progression，the biomechanical interventions for its treatment and re⁃habilitation and research on tai chi biomechanics and on its effects on lower-limb OA management.In order to develop scientific evidence based tai chi or oth⁃er exercise intervention programs for OA management，more research in joint biomechanics of the OA patients and tai chi movements biomechanics should be conducted.

osteoarthritis；joint biomechanics；tai chi；gait；moment of force of joint

G 804.6

A

1005-0000（2014）02-093-07

2013-11-04；

2014-01-28；录用日期：2014-01-29

李静先（1957-），女，内蒙古萨拉齐人，博士，副教授，上海市东方学者，研究方向为生物力学。

加拿大渥太华大学，加拿大渥太华 K1N 6N5。