Footwear has often been cited as a fundamental extension of the body. It is tasked with the responsibility of minimizing biomechanical forces and providing a comfortable and stable platform for ambulation. In the presence of knee osteoarthritis (KOA), shoes are believed to have a profound effect on the loads experienced at the knee joint. Despite this widely held belief, there is little scientific data to support or refute it. The majority of information known comes from expert opinion and from studies conducted on the hip. This is an important issue as abnormal knee joint loading is thought to be a key factor in disease progression on KOA. It is estimated that the joint reaction force, which is a measure of the load passing through the joint, increases by a factor of three to six times body weight with each step. This can rise to be ten times body weight when climbing stairs. An increase in knee joint loading is also believed to be a risk factor for the development of KOA, particularly in overweight individuals, as it may initiate a cycle of damage and repair in the articular cartilage. Therefore, if footwear has a significant effect on joint loading, it may be a modifiable risk factor for both disease initiation and progression of KOA. This leads to our research question: Is there a systematic difference in knee joint loading in a range of different footwear, and if so, what footwear characteristics drive this difference?
Importance of footwear in managing knee pain
A toolkit to prevent knee osteoarthritis has been created based on the findings of a study on people with a family history of knee osteoarthritis. A pair of shoes with modified soles that reduce impact and give greater knee support was rated as the most useful preventative tool. Finally, Singapore has an aging population with longer life expectancy and increased activity in sports, thus increasing the prevalence of knee pain. With the increasing trend of knee pain, it is essential that steps are taken to prevent disabilities that might result from knee pain, and suitable footwear is a simple yet effective tool to achieve this.
Reducing knee pain can improve and prevent disabilities in the long term. How Singaporeans go about managing the knee pain is important. Often, knee pain is between being manageable and a disability. It is not uncommon for a person to suffer from minor knee pain and yet refrain from taking part in exercise or intense activities that could actually reduce the symptoms of the knee pain or prevent further disability to the knee. In this case, there is one risk that is often overlooked, and that is the risk of increasing knee pain through not taking part in these activities. However, if appropriate footwear can decrease the symptoms of knee pain or reduce the rate of development of knee osteoarthritis (which is a leading cause of knee disability), it could be an effective tool in helping people to regain or retain a good quality of life.
Common causes of knee pain in Singapore
Arthritis is by far the most common form of knee pain, affecting more than half of the Singapore population over 60 years of age. It is the result of degenerative “wear and tear” changes in the joint, and is classified into two main types. The first is “osteoarthritis”, often considered the age-related, “wearing out” of a joint. It can occur in any joint in the body, but most commonly affects the knees. The second is “rheumatoid arthritis”, a systemic disease which affects the joints, often leading to deformities. It typically occurs between the ages of 40 and 60, and the knees are affected in more than 50% of patients. Another common cause of knee pain is being overweight. Additional weight increases stress on the knee joints, and can advance the breakdown of joint cartilage. In a recent health promotion board national survey conducted in 2010, 34% of Singapore adults were found to be overweight. This is similar to the USA, where 35% of adults aged 20 years and over were found to be overweight in a survey done in 2009-2010. Increasing urbanisation and associated sedentary lifestyle, as well as the availability of inexpensive energy-dense foods has led to a rise in prevalence of overweight and obesity in many developing countries. This suggests that knee pain related to being overweight will likely become an increasingly more common problem in countries where the population is becoming more sedentary and adopting a diet of higher energy.
Factors to consider when choosing footwear for knee pain
Footwear characteristics studied in the context of clinical trials have included differing levels of motion control, sole thickness and hardness, cushioning, sole bending stiffness, insole hardness and contouredness, and shoe weight. These investigations have been carried out with both specially designed footwear and off-the-shelf shoes. The choice of appropriate control shoes for use in clinical trials is particularly important when studying the effects of footwear on knee OA. This is relevant to our development of a footwear classification system, as conducted in this and a previous study with different sets of shoes. Perception of shoe effects, revealed through qualitative studies, has been taken into account when selecting footwear characteristics for our classifications.
Custom footwear has been prescribed to reduce pain both locally and at the knee in patients with knee OA. Qualitative feedback from patients suggests that footwear can have both positive and negative effects on knee pain. However, there is little scientific evidence relating to the effects of footwear on symptoms or disease progression in knee OA.
Proper arch support and cushioning
A shoe’s arch support and cushioning could critically impact on an individual’s quality of life. The arch of the foot is the gap between the sole and the ground when standing and is a vital part of the human musculoskeletal system. Arch support in shoes optimally should resemble the natural contour of the arch and distribute weight evenly. However, arch height can vary significantly between individuals and too little or too much arch support can be detrimental. Flat-footed people with low arches face a greater risk of knee osteoarthritis, but there is little evidence related to footwear and arch support. People with severely high-arched feet are more prone to knee pain due to the rigid stability of the foot and impact transmission. Excessive pronation is a contributory factor in many knee injuries and is effectively reduced by a medial post in the shoe. This is stiffer material under the arch, which prevents the foot from rolling inwards, and the shoe selection is highly specific to individuals with differing foot types. Despite the common belief, there is no correlation between the prescription of custom insoles and a reduction in knee pain. The knee joint is heavily loaded during everyday activity and dynamic tasks, and studies have shown the use of a lateral wedged insole to be effective in the reduction of medial knee joint loading. This is a current topic of research at the time of writing, and there is growing evidence for its use in the management of knee osteoarthritis. Arch support and its effect on load distribution at the knee is important but is often overlooked, and there is opportunity for further research to provide more specific footwear guidelines.
Shoe stability and motion control
Sometimes, some people nowadays are avoiding to wear shoes which have stability and motion control because they think it is almost the same with athletic shoes and heavy to use. But when people come back to reality, all the shoes with stability and motion control have the same function to help decrease overpronation. A good or right motion control shoe can help in steadying your feet if you have a problem with flat feet, making you more focused and stable while at work. Usually, stability shoes are more lightweight compared to motion control shoes, but both of them have a dense material on the insole to reduce overpronation. Overpronation is a condition when your feet are too curved inside, which could cause knee pain. High-arched people also require better stability in shoes to prevent supination, which is the opposite of overpronation. Special supination shoes are rarely found, but they can be replaced with high-quality cushioning shoes. However, it is still recommended to wear shoes with stability and motion control and purchase a proper custom orthotic to deal with this problem. When choosing the correct stability or motion control shoes, try to buy them in the afternoon. This is because your feet are slightly larger than in the morning due to the effects of working all day. Do not buy narrow shoes because of the assumption that they will become soft and loosen over time. In knee pain conditions, a wrong choice of shoes can worsen the situation. Check if the shoes have enough stability by bending them in the middle. If they tend to the side, the shoes are not good for stability and motion control. Change your shoes regularly every 400-500 miles of walking or every 3-4 months for the best foot conditions.
Impact of shoe sole material on knee pain
An Australian study of 350 adults found that knee OA was related to increased lateral foot force, and this was associated with increased pain and joint damage on the medial tibiofemoral compartment. This lateral foot force may be detrimental to knee OA patients if it is not being absorbed by the shoe cushioning in a sufficient manner, and indeed the use of laterally wedged shoe insoles made from foam materials, leather, and cork have been shown to reduce this force. However, the role of shoe cushioning type and its ability to absorb/shunt forces at the knee joint is an area that demands further research before any definitive recommendations can be made.
Step-in footwear comfort has been assessed in 12 healthy females, and it was found that there were plantar pressure and comfort perception changes between different shoe cushioning density levels. However, to date, there has been no research specific to those with knee OA that shoe cushioning materials are related to clinical knee symptoms, and several patients have noted that while cushioning materials were comfortable, they felt unstable when walking. These patients felt that soft cushioning materials had increased their likelihood of knee buckling in the face of weakened quadriceps muscles, and OA patients with neuropathy also have noted balance problems with these shoes.
With that in mind, we must take into account that there are many types of cushioning materials on the market, and these range from standard EVA foams to viscoelastic materials and gels. The Mechanical and Aerospace Engineering dept at the University of California found that the use of ‘softer’ midsole materials of modern athletic shoes provided greater shock attenuation during the loading phase compared to older style athletic shoes, and this is certainly a desired effect for protecting joints in lower limb OA patients.
Articular cartilage is a connective tissue that behaves like a smooth, slippery surface to cushion and facilitate movement of joint surfaces. It is now clear that when that cartilage is damaged or lost, the subchondral bone remodels, and there is increased stress on the joint, which causes pain and further damage to the cartilage. A common question today is whether ideal shoe cushioning can offload the diseased knee joint and provide symptomatic relief for OA patients.
Soft and comfortable shoes became popular in the 1970s, and there were reports that these were better for sore knees. In the years since, shoe companies have been advertising heavily about the cushioning properties of their shoes. These claims are appealing to consumers because many people with knee OA feel that their knees are ‘bone on bone’ and are in need of cushioning. Indeed, recent data from the multicenter National Institutes of Health (NIH) Osteoarthritis Initiative (OAI) suggests that knee OA is related to the presence and site-specific loss of lower limb joint cartilage.
Types of footwear recommended for knee pain relief
Baldwin and Parvizi stress the importance of suitable footwear for knee pain reduction and prevention. This includes orthopedic shoes or any shoes that can accommodate orthosis or custom inserts. They are intended to take the individual’s weight across the foot/feet and reduce force around the knee joint. While shapes and designs vary, a common role of orthopedic shoes is to alter weight distribution pattern across the sole of the foot. Studies have demonstrated that this can reduce excessive force upon the knee and have a positive effect on surrounding tissues. Customized orthosis or shoe inserts can act in a similar way. They are known to improve pain and function in people with disorders of the knee by correcting mal-alignments or abnormal joint loading that can be contributing to symptoms. Orthosis, shoe inserts, and specialized shoes are widely used in the treatment of knee osteoarthritis and are considered to be an effective non-pharmacological approach. Its low cost and minimal risk nature make it an attractive option for those wishing to avoid medication or more invasive interventions. A recent systematic review showed that use of laterally wedged insoles significantly reduced pain in patients with medial compartment knee osteoarthritis. This is just one example of how shoe inserts can be beneficial for a specific knee condition. Laterally wedged insoles can, of course, be placed into a variety of shoe types, translating the effects to a wide range of patients. Due to their importance, clinicians should be knowledgeable in footwear options and prescriptions relevant to their patient’s knee condition.
Orthopedic shoes and inserts
Overall, the beneficial effects of orthopedic footwear and orthotic devices are generally long-term and are a simple, yet relatively inexpensive way to alleviate knee pain.
A study found that patients with the use of lateral wedge orthotic insoles in a specific shoe for knee osteoarthritis reported reductions in knee pain and analgesic use.
Besides shoes, orthotic insoles, arch supports, and custom-made shoe inserts are also widely available and can be used in normal footwear to provide the same effects as orthopedic shoes. However, it is important that when choosing orthotic devices, they should be specific to the foot disorder and the shoes in which they are going to be used.
A wide variety of orthopedic shoes exist in the market because there are many different foot types and conditions. Individuals are recommended to take time to find a pair that matches their foot type and try out different brands as characteristics can vary from one to another. This may involve the assistance of a podiatrist.
A study found that patients who wore new shoes with appropriate characteristics experienced significant reductions in the knee adduction moment and improvements in function.
Research has shown that knee pain is twice more likely to occur in older adults with foot pain or flat feet. Orthopedic shoes aim to support the natural shape of the foot, stabilize the heel, provide adequate cushioning, and reduce excessive motions of the foot. This, in turn, will help to relieve pain and prevent further aggravation of knee conditions.
Orthopedic shoes are specifically designed with the purpose of providing comfort, support, and pain relief to individuals suffering from various foot and knee conditions. In Singapore, orthopedic shoes are a common recommendation by knee pain specialist for patients with knee pain. The main reason is that knee pain in the elderly is closely linked to foot problems.
Athletic shoes for knee pain
Athletic shoes are generally the best shoes for knee pain because they have been specifically designed to lessen the shock to the legs that is created from running and other activities that cause the feet to pound the ground. Studies have shown that by wearing athletic shoes when knee pain first presents itself, the development of osteoarthritis can be slowed and even halted in some individuals. The key to finding an athletic shoe to help alleviate knee pain is to find a well-cushioned shoe with good shock absorption and arch support. Although many basketball shoes offer the above-mentioned features, they may not be the best knee pain reliever because of the higher midsole, which is designed to help in ankle support. A high midsole causes more of a load on the knee, which in turn causes more pain. The best shoe for knee pain in terms of comfort and shock absorption is a running shoe. The midsole of the running shoe has more cushioning, which is better for your knee. Some features of a good running shoe for knee pain include less mileage on the shoe, deep cushioning in the midsole, good shock absorption, and a straight last (see picture a). It is important for the individual with knee pain to wear the proper footwear even when participating in activities of daily living. Studies have been conducted recently that cross trainers do not offer enough cushioning and shock absorption to efficiently protect knee joints. Because of this, when an individual is trying to decide the best shoe for knee pain, running shoes are always the best choice.
Choosing the right shoes for specific activities
Running is possibly the hardest impact activity for knee pain sufferers. Studies have shown that a 10 minute run results in knee joint pressures equating to 1 hour of walking. For this reason, the most cushioned and supportive shoes are required. The Asics Gel-Foundation is built for maximum motion control and stability. The broad based platform and maximum support and cushioning at the heel make this shoe ideal for those with severe knee pain and knee osteoarthritis.
Best cushioned athletic shoes for walking: The New Balance 847 is an excellent choice for those who like a very well cushioned walking shoe. With good arch support, and a one and a half centimeter difference in heel to forefoot height, it allows for the option of a custom made orthotic if you should need one. The Rollbar technology assists in rear foot movement control and combined with the shoe’s light weight is a great package deal.
The right shoes can provide much comfort and convenience for the patient, while the wrong shoes can exacerbate the discomfort and pain by setting the foot in an unstable, wounded position where the natural shock absorbing of our feet and shoes does not occur. This can be the deciding factor in a patient’s ability and willingness to take up exercises for knee pain, so it is an important issue to address. There is in general no harm using the best cushioned athletic shoes for all activities if it is difficult to find adequate alternatives. Below recommendations are mainly for those who want to go the extra mile in minimizing stress on their knees, and are looking to use footwear as a tool to achieve this.
In summary, despite the biomechanical studies alluding to the perfect shoe type, there is no single best shoe type that will suit everyone’s needs. Patients seeking orthopedic footwear advice should be evaluated thoroughly before a shoe type can be recommended for them. For patients with knee osteoarthritis, our study suggests that an individually preferred shoe type can be found through an algorithmic process. In the future, patients suffering from knee osteoarthritis will be able to derive significant pain relief from knee OA symptoms based on footwear recommendations. Hence, it may be pragmatic for footwear-based interventions to be covered under a healthcare plan for patients with knee osteoarthritis. This will invariably save on the cost of medication and knee replacement surgeries, considering that knee OA affects a patient’s lifestyle and can occur in those as young as 40 years old. Taking into account the results of this study and existing biomechanical studies on the relationship between footwear and knee OA, more in-depth studies on the topic would be beneficial for the orthopedic community. Next steps in research could involve a focused study on each shoe type to identify a brand and model of the shoes that will further optimize the relief of knee OA symptoms. Alternatively, a longitudinal study could analyze the rate of knee OA progression in relation to specific shoe type changes.
