The Asian knee through a cultural lens
The nearly three billion people living in the Asia region have a number of social and cultural demands placed on their knee joint that need to be considered by surgeons contemplating TKR. (Lifestyle and religious practices demand high flexion, for example)
When thinking about Asia, most images that come to mind are from postcards: a worker harvesting rice from a verdant green paddy; hundreds of people universally bent low over colorful prayer mats; the unique architecture of shrines, temples and mosques; families sitting together on the floor to share a meal; vibrant urban and rural landscapes.
While these images may present a stereotypical view of the people and places within the Asia region, the scenes also reveal some of the unique demands placed on the bodies of the people who live here.
United by diversity
The cultures of the people inhabiting the Asia region are as diverse as the landscape, yet from a physical perspective a number of practices unite them. Religion, lifestyle and work each place particular stresses on the knee joint that leads to common wear patterns as well as high expectations for post-operative mobility—patients want to be able to resume these demanding activities with a higher quality of life than before surgery. Myung Chul Lee, MD, PhD, Prof., a surgeon at the Seoul National University Hospital noted that kneeling, squatting, and sitting in a cross-legged position “require almost 165 degree or full knee flexion.”
There are many seated positions in Asian cultural traditions and religious rituals. The many ancient statues of Buddha and various Hindu gods in the lotus position illustrate how integral this way of sitting is to many traditional cultures in Asia .
A statue of Buddha in full lotus position.
The World Factbook, published by the US Central Intelligence Agency (CIA) cites 22 percent of the world’s population as Muslim . Salat, or daily prayer, is required five times a day for both men and women from the age of seven. This translates into 70 hip and knee flexion each day , which is not insignificant, especially when considered in addition to everyday activities.
Asian Muslims religious activities develop, encourage and maintain higher range of motion (ROM). Muslim prayer includes standing, bowing, sitting and prostration. A 2015 study by Ariff et al  aimed to determine the average ROM for hips and knees in young Malaysian men [mean age = 22] during various prayer postures [See image below]. The researchers found that the sitting posture demanded the most flexion from the knee (152 degrees) while maximum flexion for the hip was seen during prostration (141 degrees). They noted that ROM declined with advanced age.
The researchers also pointed out that when compared to similar ROM studies with subjects from other countries (Iran, Saudi Arabia) their data varied by 10 to 20 degrees, indicating a cultural and geographical influence. They suggested orthopedic specialists should determine normative ROM data for local populations.
In a 1991 metastudy of ROM in US subjects Roach and Miles  stated that Western textbooks report a wide range of ‘normal’ knee ROM: from 130 to 150 degrees. African American and Caucasian men (average age = 32) were found to have mean ROM of 128 and 134 degrees, respectively—significantly less than what was reported in the similarly aged population in the Malaysian study.
Knees of Saudi Arabian patients undergoing TKR showed “more pronounced anteromedial and posterolateral cartilage wear patterns” when compared to similar North American patients . Those with ACL-deficient knees showed the worst cartilage wear. They attributed the cultural practices of squatting or kneeling to altered knee mechanics and differing wear patterns.
In addition to religious requirements, lifestyle activities also contribute to the need for high knee ROM in the Asian population. Many daily activities take place while on the floor or ground in squatting, or cross-legged positions.
Praying force the knees into deep flexion.
When interviewed in TheNational , a United Arab Emirates news source, Charles Brown MD, the director of the Abu Dhabi Knee and Sports Medicine Center, hypothesized that lifestyle may be one of the contributors to the higher prevalence of knee injuries and early onset osteoarthritis in Arab populations: “people of this region tend to sit on the floor and cross-legged more, or sit on lower couches that cause them to bend their knees differently”. He shared data that showed 1 out of 600 people in the Emirates have anterior cruciate ligament (ACL) injuries compared to 1 in 3,000 Americans.
In Korea, home design has evolved around an underground heated floor called ondol or gudeul . Because of this Korean families traditionally sit, sleep, eat and work on the floor. At night bed pads are unrolled on the floor for sleeping . Koreans of all ages need their knees to bend deeply for these activities.
Japan also has a cultural legacy of eating while seated on the floor . Traditional Japanese furniture is low to the ground, demanding knees to lift one up and down a considerable distance when rising. In this country, tatami mats  cover the floor and a soft mattress rests directly on top for sleeping.
Similarly in rural India much of a day’s activity, notably cooking, is conducted from a squatting position on the ground. Like in Korea and Japan, eating is also done in the cross-legged or squatting position and from an Ayurvedic, a traditional Hindu medicine, perspective this is seen to assist digestion and calm the mind .
In China, squatting is a daily occurrence for many. A study that looked at the association of this posture to the prevalence of radiographic osteoarthritis (OA) in Beijing residents compared to Framingham, US residents, found that “prolonged squatting [>1 hour/day] is a strong risk factor for tibiofemoral knee OA among elderly Chinese subjects” . [See part 2 “Anatomical considerations” for more information on the anatomical specifics of Asian knees.]
Interior of a traditional Korean home where one sits on the floor.
Working on the knees
Within Asian cultures the prevalence of knee OA is more common than in Western Caucasian populations. In addition it is more pronounced in women than in men. For example, the South Korean national registry data has shown that the TKR surgery rate in Korea is less for men than for women . A group of researchers also found that radiographic knee OA is 3.5 times higher and symptomatic knee OA 5.2 times higher in Korean women compared to Korean men .
Women in Asian countries, particularly those living in a rural setting, can spend many hours a day squatting for cooking duties, childcare, and household and farming chores (rice planting and harvesting). In addition to OA and other knee wear patterns, bilateral peroneal nerve palsy has been linked to prolonged squatting .
For the bulk of the population in Asia hole toilets are the reality. It’s been estimated that 4 billion people globally  use this style of toilet and a full deep squat is required. It’s just another example of how the Asian population incorporates deep knee bends and squatting actions on a daily basis.
Predictor of mortality?
While a wide range of motion in the knee is desired by Asians to maintain a culturally appropriate and active lifestyle, the need to be raising and lowering oneself for prayer and other activities may have additional benefits, such as improved musculoskeletal fitness.
Researchers from Brazil and the US looked at the ability to sit and rise from the floor as a predictor of all-cause mortality. They found that for the 2002 subjects (aged 51–80) “each unit increase in SRT score conferred a 21 percent improvement in survival” . On the other hand, despite maintaining a certain level of physical ability to raise and lower oneself from a seated position, those who sit for prolonged periods have been shown to be at risk of heart disease and diabetes mortality and increased cancer risk is suspected but not yet scientifically established [19, 20].
A changing population
With a higher incidence of knee OA in Asian populations, particularly in Asian women , established we turn to why this is the case. Clearly, lifestyles and religious practices impact the health of the knee as deep, repetitive actions wear the knee joint. There are also anatomical differences between Asian and Caucasian knees that have been shown to predispose the Asian knee to OA. (See part 2 “Anatomical Considerations” for more information on the physical specifics of Asian knees.) However, there are also emerging population trends that influence both the incidence of knee OA and the rates of TKR surgery.
Obesity stresses knees
Obesity rates are rising all over the world. It is a phenomenon seen in both adults and children. With over 1.5 billion adults classified as overweight and obese, and 200 million children overweight, the world is facing a very serious public health crisis. It has been predicted that this generation will be the first with a shorter life span than their parents .
In addition to multiple comorbidities, obesity has been shown to be a risk factor for knee OA . “Multiple linear regression analysis show that there is a significant linear negative relationship between BMI and ROM of knee” .
Rising child and adolescent obesity rates will place pressure on healthcare resources in the future and are worrying for healthcare professionals, insurers and governments. It is within this young age group that obesity is increasing most rapidly.
The obesity trend has been attributed to a number of factors: less physical labor as populations relocate to from rural to urban environments; higher levels of food consumption; as well as cultural, social, educational and economic factors .
When looking at joint pain in affluent and poor residents of Karachi, Pakistan researchers found that knee pain was reported more often by more affluent study participants (3.3 percent) compared to the poor (1.8 percent). Knee pain also was indicated more than other types of joint pain. Body weight was significantly higher in the affluent participants and also regularity of prayer. It was concluded that despite more squatting in the poorer participants, it was relative obesity that resulted in “greater frequency of knee symptoms” .
The National Institute on Aging succinctly highlights the global aging trend.
“The world's population is growing—and aging. Very low birth rates in developed countries, coupled with birth rate declines in most developing countries, are projected to increase the population ages 65 and over to the point in 2050 when it will be 2.5 times that of the population ages 0-4. This is an exact reversal of the situation in 1950” .
In Southeast Asia (Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar (Burma), the Philippines, Singapore, Thailand and Vietnam—known as the Association of Southeast Asian Nations (ASEAN) the rate of increase in numbers of the oldest old (aged 80 years and older) is projected to exceed that of East Asia over the period 2025–2050 .
Knee issues are more prevalent in the elderly. In fact, TKR is one of the most common procedures for this demographic . However, there is also a growing trend for younger TKR patients. In an interview with the American Academy of Orthopedic Surgeons (AAOS) Kevin Bozic, MD, MBA noted that TKR patients were younger and they had higher expectations for the procedure. “In 1999, about 30 percent of TKA patients were younger than 65,” said Bozic. “In 2008, patients younger than 65 accounted for 41 percent of all TKAs. And, as our patients get younger, they expect that they will be able to do more with a TKA.”
According to Myung Chul Lee, MD, PhD, Prof, a surgeon at the Seoul National University Hospital, he is increasingly encountering young, active people in his practice who require TKR.
Clearly there are a number of factors specific to Asian people that play a part in the frequency of TKR. Cultural practices, lifestyle activities and a growing obesity rate in an aging population contribute, but there is also another category to consider.
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