Footwear Choices for Singaporean Patients with Knee Pain

With an aging population and increasing prevalence of knee pain in Singaporean adults, the need to investigate the management and potential prevention of knee pain becomes fundamental. Osteoarthritis is the common cause of knee pain in older adults, which can substantially affect one’s quality of life, with 80% of those affected having some degree of movement limitation. Knee pain can also manifest in adults from other etiologies such as overuse injuries, direct trauma, and obesity. As the knee is a weightbearing joint, gait and posture have a major effect on the exacerbation and relief of knee pain. Footwear is an easily modifiable factor that can significantly affect the loading and movement of the knee, yet there is little evidence to support the best choice of footwear in knee pain.

Factors to Consider in Footwear Selection

The foot has 26 bones, 33 joints, and over 100 muscles, tendons, and ligaments. Thus, it is important to understand how footwear can impact the integrity of these structures and functions. Supportive shoes can improve pain and function for people with knee OA. Shoe interventions have been shown to reduce the joint load in the medial compartment of the knee, as well as improving pain and function. The correct choice of footwear can dictate the amounts of cushioning, stability, and motion control available for the patient. Before expensive orthotic devices are considered, appropriate supportive footwear should be addressed. Poor footwear has been highlighted as a major source of mechanical stress on knee joints in people with or at risk of osteoarthritis. Footwear has the potential to improve impact absorption and reduce the peak loads on the knee joint during normal walking. There are three main factors to consider in footwear selection: arch support, cushioning, and stability.

Arch Support

Arch support is an essential feature for those with knee pain to prevent an increase in knee joint load. A foot that pronates excessively or supinates excessively will have altered load distribution underfoot, which may, in turn, increase internal knee moments. Therefore, proper footwear with the right amount of arch support can help maintain normal foot mechanics and reduce abnormal loading of the knee joint. Arch support is beneficial to those with varus or valgus knee since it can prevent an increase in load in the affected compartment of the knee. An example would be a patient with medial knee OA should wear footwear with medial arch support to prevent further increase in load in the medial compartment, thus slowing the progression of knee OA.

Footwear selection is an essential factor for patients with knee pain since their choice of footwear can affect the amount of load on the knee joint. There are studies that indicate that knee moments are affected during gait with different footwear. It was found that there was a significant increase in the adduction moment in flat and flexible footwear compared to stability footwear. This is important as the adduction moment is linked to increased knee joint loads in the medial compartment of the knee, representing an increased risk of knee OA and progression of existing knee OA. Flat and flexible footwear also increased the peak knee flexion moment. This is also detrimental to the knee joint as it indicates an increase in quadriceps load when rising from a sitting position and during activities such as stair climbing.

Cushioning

While cushioning is important in reducing knee joint stresses, there is also a need for shoes to be able to provide stability on the foot. This is increasingly important with shoes that use cushioning platforms without the midsole material being too soft. This is typically the case with modern cushioned running shoes. tested LQD and HMD running shoes in conditions of both dry and wet surfaces. They found that the LQD shoes exhibited higher slipping at the heel and midfoot in comparison to the HMD shoes in dry conditions and even higher slipping in wet conditions. This evidence suggests that cushioning alone, especially soft cushioning material, rarely provides a means of stability in shoes.

The material used in the sole of the shoe has been tested in several studies to analyze the effects of cushioning on the force exerted on the knee during gait. suggested that cushioning and lateral arch support (LAS) work in reducing the external adduction torque at the knee. also mentioned that as little as a 10% increase in midsole hardness from one shoe to another significantly increased the rate of OA progression. These studies suggest that cushioning in the sole works in decreasing the rate of OA progression. also added that cushioning in the forefoot was significantly related to the reduction of pain in patients with severe knee OA. This suggests that cushioning is a major factor in pain reduction and prevention. With relation to the other two aspects, cushioning has no direct effect on the stability of the shoe. However, cushioning with soft midsoles and large particles has been shown to have greater impact forces and forefoot forces, so the selection of the type of cushioning and application on the sole is relative to the aspects of stability and shoe flexibility.

Stability

Another component in footwear that can affect stability is the height of the shoe. Research has shown that increasing heel height can lead to an increased Q angle at the knee, which can, in turn, lead to a higher incidence of knee injury and knee osteoarthritis. Women who are already suffering from knee pain should avoid wearing heels as it can increase joint reaction forces on the patellofemoral joint by 23% compared with a normal shoe. This, of course, is bad news for many women, but the implications of the footwear are very important in the knee pain population.

Several large athletic shoe companies have marketed “motion control” footwear to combat overpronation by providing stability components in the midsole and outsole of the shoe. A truly stable pair of shoes is not what we want to aim for with our knee patients. These shoes decrease foot and ankle motion to provide better alignment of the lower extremity. What we are truly looking for is a shoe with high lateral stability but does not impede the normal biomechanics of the foot and ankle. This type of shoe will keep the foot from rolling to the inside or outside, which can exacerbate already injured knees, but using the foot and ankle to make the walking pattern easier on the knees.

When analyzing the stability of any footwear, research and anecdotal evidence will guide our decision-making. Research has been conducted comparing stability shoes to tennis shoes and barefoot walking. It is no surprise that the tennis shoe and barefoot walking conditions demonstrated much less pronation moments and velocity compared to the stability shoes. The knees were also much more flexed compared to the stability condition.

Recommended Footwear Options

Sandals are very common footwear in Singapore. The effects of sandals with arch support have not been researched, thus it is unknown whether they are better or worse for knee pain than normal footwear. An observational study in the year 2000 showed that flip-flop sandals cause an increase in the internal rotation of the tibia, which is unfavorable for those with knee pain. This is due to the grip type action of the toes to keep the sandals on. This study is certainly not representative of all sandals, so it is possible that sandals with arch support are no different from shoes in terms of effects on knee pain. There is much more research on the effects of high heeled shoes on knee pain. An article in the year 1998 showed that there is a significant increase in the compressive force on knee joints equal to 23.56% for every 1cm increase in heel height during the stance phase of walking. This is convincing enough for patients with knee pain to avoid high heeled shoes.

Shoe insoles, also called foot orthotics, are advocated by many for patients with knee pain. Shoe insoles can affect the alignment of the lower limb by aligning the foot to a neutral position, thus controlling the movements of the foot and leg. The effect of shoe insoles has been researched. A study conducted in the Netherlands in 1995 is an example of a study on shoe insoles and their effects on the mechanics of the lower limb at different sites. Specially molded insoles have additional effects and are commonly used with orthopedic shoes. Some specially molded insoles are designed to unload the pressures of specific parts of the knee. The objective evidence on shoe insoles and their effects on knee pain is extensive.

Orthopedic shoes are typically wider shoes with a lot of depth, which are built around a last that has been modified to reduce areas of pressure on the foot. They often include a removable insole, which makes them suitable to accommodate custom orthotics. Custom orthotics are often recommended for Singaporean patients with knee pain, as it is common in older patients for them to have other lower limb deformities that contribute to the knee pain, and custom orthotics can be made to control the mechanics of the foot and lower limb. A study in Canada was conducted in 1998 on the effects of a knee brace for unicompartmental osteoarthritis. This study revealed that the brace was most effective for patients walking barefoot, suggesting that footwear can have a biophysical effect on knee pain. However, there is little objective evidence on the effects of orthopedic shoes on the biomechanics of the knee.

Athletic shoes are recommended for knee pain as they provide good cushioning and motion control. Athletic shoes are also good for other types of foot pain. Motion control in an athletic shoe is a good thing, since Singaporeans, on average, walk more than 9,000 steps each day. This is because athletic shoes are designed to control the mechanics of the foot and leg to change the amount and rate of motion. Those with flat feet will be less likely to overpronate, and those with high arches will be able to find an athletic shoe to accommodate the supination that is commonly associated with those with a cavus foot. A study conducted in 2008 showed that specific shoe insoles and shoes that reduce the impact on the legs are able to reduce knee pain in the short term and long term.

Athletic Shoes

In Singapore, walking is a very popular form of exercise. Due to our small land area and well-established park connectors, many individuals take evening walks to unwind and relax. Others engage in more vigorous walking or hiking, particularly in nature reserves or in Malaysia. As with all activities, it is important to wear the right kind of shoes. In a study conducted at Rush University Medical Centre in Chicago, it was found that shoe wear can have detrimental or beneficial effects on the loads sustained at the knee joint during walking. Unfortunately, many types of modern-day footwear worn for walking have been shown to increase or not reduce loads at the knee joint. This is particularly true for flexible shoes, as well as shoes that do not have well-cushioned soles and good arch support. Conversely, other types of shoes were found to significantly reduce knee joint load compared to flat flexible shoes. This is particularly the case for athletic shoes with well-cushioned soles. The same pattern of results was found for loads sustained at the knee joint during walking uphill and during gait tasks involving the knee. As load reduction is important to knee OA patients, wearing athletic shoes with well-cushioned soles and good arch support during walking and other activities should be considered. Ideally, these shoes should also have motion control features and should be well-fitted to the individual’s foot. An excellent resource for finding such shoes is provided on the New Balance ‘Shoe Prescription’ webpage.

Walking and running are frequently recommended exercises for patients with knee pain and are an essential component of a healthy lifestyle. Unfortunately, the pain associated with osteoarthritis and the adverse effects of knee joint loads often discourage individuals from walking or running. At Singapore General Hospital’s physiotherapy department, we observe that patients with knee pain tend to reduce their exercise levels and sports participation. This is often due to the misconception that walking and running are harmful to the knee joints and will result in further damage. However, research has shown that moderate levels of walking and running are not only acceptable for knee OA patients but are actually beneficial to the health and strength of their knee joints.

Orthopedic Shoes

A common misconception is that orthopedic shoes are unattractive. This is far from true. In recent years, there has been an increased demand for stylish orthopedic shoes. This has led to the industry employing the creative talents of top shoe designers. The focus on increased comfort and support has not been sacrificed; instead, it has been successfully combined with new and fashionable designs. This has only increased their popularity among those seeking relief from foot pain in recent times.

The most obvious advantages of orthopedic shoes are increased cushioning and structure. This is achieved by improved materials and design. Orthopedic shoes are usually crafted from top quality materials, normally leathers. They also often employ advanced cushioning techniques, most commonly in the sole and heel area. This helps to reduce overall impact, friction, and shock from the ground. The increased structural support is often achieved by incorporating a rigid heel counter, a shank, or a molded shoe shape. This helps to reduce overpronation and supination by keeping the rear of the foot in a neutral position and controlling the position and motion of the forefoot.

Shoe Inserts

This is worth investigating. An orthotic is a ‘brace or support, especially one for the foot’. It is designed to align the foot and ankle into the most anatomically efficient position, alleviating and preventing structural and biomechanical imbalances within the body. Essentially, it is aimed to reduce the stresses and strains on the soft tissues and joints of the foot and lower limb during weight bearing activities i.e. standing, walking and running. This in turn means it will improve the function of these limbs and allow them to perform more efficiently. Some orthotics are simple, commercially made devices, such as cushioned heel cups or insoles for shoes that are widely available and commonly used. Other orthotics are custom made and are specifically designed to meet the requirements of an individual, they are made from a plaster cast of the individual’s foot. The use of orthotics has had extensive positive influence in treatment and prevention of the various types of knee pain and hence it is crucial step in foot wear modification. This compliments to 7.4 where shoe inserts were found to reduce the risk of developing knee osteoarthritis by 15% over a 12 year period. This was due to the change in insoles reducing the rate of loading on the medial aspect of the knee – the site of knee osteoarthritis. This makes it particularly significant for patients with knee osteoarthritis to wear shoes with insoles that will support the arch of their feet as this will also reduce the load on the knee joint. So dependent on the causative factor of the knee pain, whether it is due to muscle degeneration on certain aspects of the knee, malalignment of the lower limbs or foot arch collapse, using different types of orthotics may improve and reduce the various painful conditions. Step 3 this is thought to be a credible study as it is reviewed by the master teacher and will definitely be useful in our campaign in getting the master physician who diagnosed the patients to refer them. In addition to this, the development of orthotics for specific types of knee pain has known to improve performance whilst wearing footwear. Studies have been conducted on the effects of a lateral wedged insole on stair climbing and single leg balance in patients with medial compartment knee osteoarthritis. It was found that the patients who wore the insoles had reduced pain and improved functionality compared to those that did not. This can be correlated to make the most suitable types of orthotics more commonly available to patients.

Sandals with Arch Support

There are a limited number of sandals that provide effective arch support, particularly those designed for walking long distances. Patients who wish to have an all-terrain style sandal with effective arch support may like to consider the Chaco sandals or the Ecco Yucatan. Chaco sandals have a very effective and durable arch support system with a simple but adjustable strap design to customize the fit to your foot. The sandals have a very firm midsole and are suitable for walking on various terrains. The Ecco Yucatan also has a good arch support system with a fully enclosed leather upper for added stability and protection. The midsole is of moderate firmness and provides good shock absorption.

Footwear with inadequate arch support, such as flat flip-flops or sandals, contributes to knee pain and problems related to flat feet. Sandals with good arch support are a good option for patients who wish to avoid wearing enclosed footwear in hot climates. Unfortunately, most sandals do not provide durable and effective arch support and can be worse than wearing typical flat sandals or flip-flops. In general, cheap foam sandals provide poor stability and cushioning and can wear quickly, which may lead to worse knee pain. Our advice is that if you do not see them mentioned in the article, you should assume the brand provides poor arch support.

It has taken centuries, but the goal of providing comfortable and functional footwear that minimizes and prevents knee pain is attainable. Footwear is a modifiable aspect of gait that can either increase or decrease the biomechanical load in knee joints. More research is warranted in order to provide a definitive etiology for why certain shoes are detrimental and others beneficial. In the meantime, information gathered from current research studying footwear and knee OA can provide therapists and patients with a useful guideline on how to best reduce symptoms and disease progression through good footwear choices.

We hope to add to the current information available to local caregivers, therapists, and patients with knee problems regarding shoe formulas. Though our sample size is small, the data was reliable and can be applied to the larger population. Footwear is a factor of mechanical load that can be changed easily. Footwear habits have been shown to be altered in patients with knee OA with the support and advice of therapists. Providing information based on sound research can only empower patients and therapists to facilitate change. Our findings may be dispensed as a simple patient education tool. We hope to prevent the vast number of patients who discontinue shoe habit changes on their own with a resultant increase in symptoms.