In this blog post, we’ll explore the importance of joints—which enable our bodies to move—as well as advancements in artificial joints and wearable robot technology.
Why are joints important?
As smart technology has advanced, people have become able to accomplish more tasks without moving around as much as they used to.
With just a smartphone, we can talk to people far away without even stepping outside, and thanks to advances in artificial intelligence and various interface technologies, the ability to control machines with just a thought or a simple gesture is gradually becoming a reality. However, this does not mean humans can live without moving for even a single moment. We must move simply to meet our basic needs for food, clothing, and shelter, and most activities—such as communication, exercise, and leisure—ultimately require us to move our bodies directly. Although we spend our entire lives moving, we often do not give much thought to how we are actually able to move or what lies at the core of movement.
How do we move? It is well known that our arms and legs move as muscles contract and relax. However, fundamentally, it is the existence of joints that allows us to move to desired positions and perform a variety of actions. Joints are the points where bones connect to one another, consisting of articular cartilage, synovial fluid (joint fluid), the joint capsule, and ligaments. It is because of joints that our bodies are not a single rigid structure, but rather a structure in which each part can move freely. We can bend our fingers and pick up objects because of our finger joints, and we can move our legs forward and backward to walk thanks to our hip and knee joints. In addition, rotational and flexion movements centered on joints occur in various parts of the body—such as the spine, jaw, elbows, wrists, ankles, and shoulders—enabling us to move freely.
With the exception of actions like blinking or making facial expressions, most bodily movements involve rotation or flexion around joints. In other words, joints play a vital role in human activity. So, can joints be used indefinitely? The cartilage that makes up joints can gradually wear down over time and is affected by aging, overuse, and trauma. Furthermore, strenuous exercise or repetitive impact can strain the joints, leading to cartilage damage and inflammation. Synovial fluid lubricates the joints and absorbs shock, but if joint function deteriorates due to various causes, pain and limited mobility can result. The hip joint, in particular, is located in the pelvis and bears the weight of the upper body while facilitating movements such as walking and running, so it is constantly subjected to heavy loads. Of course, conditions such as intervertebral disc disease in the spine and injuries to the knees and elbows are also common. While symptoms can sometimes be alleviated through medication, physical therapy, or exercise therapy, in cases of severe damage, patients have no choice but to seek help from treatment technologies that combine mechanical engineering and medicine. These methods can be broadly divided into two categories.
How do artificial joints replace natural joints?
The first method involves implanting an artificial joint into the body to replace the natural joint. Although various studies to replace damaged joints have been conducted since the 19th century, early attempts failed to adequately address issues such as pain and durability. Later, in the 1960s, British orthopedic surgeon John Charnley developed a low-friction artificial hip joint, laying the foundation for modern joint replacement surgery; since then, related technologies have advanced rapidly. Initially, various materials, including polyethylene, were used, but over time, concerns arose that microparticles generated by wear and tear could affect surrounding tissues. Today, artificial joints that combine various materials—such as high-durability polyethylene, ceramics, and metal alloys—to reduce wear and extend service life are widely used.
Since artificial joints are devices designed to function similarly to natural joints, patients can move relatively naturally after surgery; furthermore, because they directly replace the damaged joint inside the body, there are almost no noticeable changes in appearance.
Furthermore, advances in medical technology have significantly improved surgical success rates, and these procedures are now widely performed, particularly for hip and knee joints. However, even with highly durable materials, long-term use can lead to wear and tear or loosening. While the lifespan of modern artificial joints varies depending on an individual’s activity level and health status, many cases show they last 15 to 25 years or more, and in some instances, even longer. However, if the implant reaches the end of its lifespan or complications arise, revision surgery may be necessary. Since this requires reopening the joint area, it can be burdensome for elderly patients; furthermore, although rare, complications such as hypersensitivity reactions to metal components or infections are possible, so thorough consultation and careful consideration are essential.
Could wearable robots be a new solution for joint problems?
The second approach involves the use of wearable robots. When people hear the word “robot,” they often first imagine a fully functional, self-moving form like a humanoid, but in reality, robots come in a much wider variety of forms. Even the special suits featured in movies can be considered a type of wearable robot in a broad sense. These devices serve to assist human movement or augment muscle strength.
Wearable robots, which once seemed like technology confined to the movies, are now being utilized in real-world industrial settings and the medical field. In the early stages, military research was actively conducted to transport heavy equipment or enhance soldiers’ mobility. BLEEX (Berkeley Lower Extremity Exoskeleton), developed at the University of California, Berkeley (UC Berkeley), is one of the most representative early exoskeleton robots. This device is designed to assist the user’s movement by applying an exoskeleton structure to the lower body, and it was developed to carry heavy loads with less effort by utilizing a hydraulic system and computer-controlled technology. This research subsequently served as a crucial foundation for the development of various exoskeleton robot technologies.
Recently, the range of applications for wearable robots has become even more diverse. Commercialization is taking place for a wide variety of purposes, including not only the military sector but also rehabilitation therapy, industrial settings, gait assistance for the elderly, and mobility support for people with disabilities. Exoskeletons incorporate joint structures, electric actuators, and various sensors to analyze the user’s movements in real time and provide the necessary amount of assistance. Thanks to this, even people with weak muscle strength can walk or climb stairs more steadily, and the physical strain on workers who must lift heavy objects can be reduced. Even now, companies and research institutions around the world are continuing their research to develop wearable robots that offer greater comfort, are lighter in weight, and allow for more natural movement.
Unlike artificial joints, wearable robots assist joint function by attaching mechanical devices to the outside of the body, without the need for internal surgery. Furthermore, they are designed to generate significant force with minimal effort, helping the elderly or people with weak muscle strength to carry out their daily lives more comfortably. From a purely functional perspective, wearable robots represent a technology with tremendous potential. However, there are still numerous challenges that need to be addressed. Since most wearable robots run on batteries, their operating time is limited, and they require recharging. Other issues remain, such as the device’s weight, price, comfort, and maintenance costs. Although their size and weight have been significantly reduced compared to the past, there is still room for improvement before the general public can wear them freely in daily life.
How far will joint technology advance in the future?
Just as the human body ages with time, joints also gradually wear down and lose function over time. To address this, one option is to replace damaged joints with artificial joints, while another is to use wearable robots that assist movement from outside the body. Although the lifespan of artificial joints has greatly improved compared to the past, they are not permanent, and replacement may be necessary depending on the duration of use and the patient’s condition. Wearable robots are also becoming increasingly smaller and lighter, but challenges remain, such as cost, battery performance, and comfort.
Nevertheless, science and technology are steadily advancing. The materials used in artificial joints are becoming more durable, and custom manufacturing and robotic surgery technologies are also developing rapidly. Wearable robots are also being improved to be lighter and move more naturally, and their applications are expanding beyond medical and industrial settings into everyday life. Someday, artificial joints that last much longer than they do now and wearable robots that anyone can wear without difficulty may become commonplace. It will be worthwhile to keep a close eye on how these technologies, which will make our lives more convenient in the future, continue to evolve.
