March 2018

The effect of footwear on the management of pain caused by disorders of the knee joint

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Clinical studies have demonstrated that properly fitted footwear may alleviate knee pain resulting from osteoarthritis or other joint disease processes, while the wrong shoe can exacerbate the condition. How can practitioners help patients with knee pain make the distinction?

By Keith Loria

Footwear plays an integral role in force distribution on the lower extremities, and choosing appropriate footwear is one of many strategies people can use to manage knee pain caused by joint disorders. When footwear is properly fit, force and stress can be shifted away from weaker parts of the knee, and the leg stabilized. This may lead to a significantly better quality of life for patients with knee problems, such as osteoarthritis (OA) and patellofemoral pain syndrome.

“The wrong footwear can contribute to the development of painful knees and exacerbation of arthritis in the knee joint,” said Justin Price, MA, corrective exercise specialist in San Diego, CA. Price recommends investigating force distribution, stability in the lower extremities, reduction of load, and patient comfort when evaluating the various types of footwear.

The problem with heels

Shoes with a standing surface not parallel to the floor due to an elevated heel, such as dress shoes, running shoes, and boots, tip the body’s center of mass forward, causing the entire body to compensate in order to avoid falling. People who wear high-heeled shoes may stand or walk with their knees constantly bent to stay upright, Price said. Over time, the sustained knee flexion may lead to inflammation, pain, and additional musculoskeletal imbalances. In addition, an elevated heel may cause an anterior pelvic tilt, where the pelvis rotates forward, tilting up at the back and down at the front and resulting in excessive lumbar lordosis and compensatory shifts up the spine to the head.

A key message is to individualize treatment. This involves thoughtful attention to foot type and type of knee compartment affected.

Kade Paterson, MSD, post-doctoral research fellow, in the Department of Physiotherapy at the University of Melbourne, Australia, said it’s now well known that shoes with higher heels increase load within the tibiofemoral and patellofemoral joints, contributing to knee pain. “Many standard athletic shoes have a heel height of 30 mm or more [higher than an inch], which can increase knee load by more than 15%,” he said. Shoes that have a lower heel height and pitch and are more flexible reduce load in these joints.

Moreover, according to Price, almost all fashion-focused footwear is problematic for the knees because it is typically designed to narrow toward the front. This narrowing of the foot width with associated compression of the toes decreases the base of support, again causing the entire body to compensate in order to remain upright.

Gregorio Caban, DPM, Doral, FL, a reconstructive foot-and-ankle surgeon, noted he often sees referred patients with knee conditions, many of whom have received a diagnosis of patellofemoral pain syndrome (PFS). “My role [in these cases] is to identify a possible deformity in the foot that is contributing to the knee condition,” he said. He treats PFS with proper foot gear and orthotics based on the patient’s foot type.

Findings from recent studies

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Although comfort and fit are very important, as an uncomfortable shoe either won’t be worn or will actually cause foot pain, it is equally important to replace shoes frequently. “In one of our recent clinical trials,” noted Paterson, “we asked participants to bring in their most commonly worn pairs of shoes and found most were very old and well worn, with an average self-reported age of 3.4 years and estimated 5240 hours of wear.”1 Avoiding foot pain is beneficial, said Paterson. “[Foot pain] exacerbates existing knee pain in people who already have knee OA.”

Jared M. Newman, MD, Department of Orthopaedic Surgery, SUNY Downstate Medical & Rehabilitation Medicine Center, Brooklyn, NY, and fellow researchers reviewed the current literature on the use of various types of footwear worn by patients who suffer from knee pain, by specifically evaluating knee OA and patellofemoral pain and the effect that different footwear had on patient symptoms.2

Newman and his colleagues found that various footwear modalities were beneficial but that the results among studies were conflicting and warranted further investigation. The authors also discovered, however, that there were several positive outcomes that could be used as a foundation for further study. For example, the review revealed that the use of wedged insoles with and without subtalar and ankle joint straps can potentially diminish symptoms by diverting forces away from the medial position of the knee, reducing joint space narrowing and subsequent pain and improving function.2

Similarly, the use of specialized footwear, such as minimalist shoes—flexible, flat shoes without raised heels—was shown to reduce pain and knee adduction moment, and therefore load on the knee joint. Reduction in joint load has been theorized to minimize the progression of knee OA and pain. Studies have demonstrated that these shoes can decrease patellofemoral pain by reducing the stress of the patellofemoral joint, Newman said.

One size does not fit all

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In another study, David Hunter, MBBS, MSc, M SpMed, PhD, FRACP, Florence and Cope Chair of Rheumatology and professor of medicine at the University of Sydney and the Royal North Shore Hospital, Sydney, Australia, and coworkers looked at the role of footwear in predisposing to exacerbations of knee pain in persons with knee osteoarthritis.3 The study found that people who had little support in their shoes, particularly in high-heeled footwear, were more likely to have exacerbations of knee pain. The study found that proper footwear appears to be important both in preventing a person from developing pain and in controlling its severity, Hunter said. Repeated physical activity over a long duration can compound the damage and resultant pain, Hunter said. “I think the key message is to individualize treatment. This involves thoughtful attention to foot type and type of knee compartment affected rather than using a 1-size-fits-all approach.”

Paterson recently led a study comparing the biomechanical effects of flat, flexible shoes to more stable supportive shoes, based on 5 key criteria–heel thickness, shoe pitch, motion control properties, sole rigidity, and shoe mass. Study participants walked in 3 shoe styles from each category, for a total of 6 shoe styles in all.4 Use of flat, flexible shoes resulted in significantly lower knee joint loads compared with stable supportive shoes. The authors reported that their results were generalizable to other shoe brands and models that meet the 5 criteria. In addition, the criteria are readily measurable in the clinic, thus clinicians are provided with a rough guide to choosing shoes that reduce knee load, potentially reducing pain.

In another study conducted by Paterson et al, people with moderate or severe radiographic knee OA (grades 3 and 4, based on the Kellgren-Lawrence [KL] X-ray grading scale) had greater improvement in knee pain while wearing an unloading shoe compared with a conventional walking shoe. Conversely, patients with mild radiographic disease (KL grade 2) had no clinical benefit with the unloading shoe, and in fact, responded more favorably to conventional walking shoes.5

“The reductions in symptoms in people with moderate and severe radiographic disease were achieved via a reduction in the knee adduction moment (a surrogate measure of internal medial knee joint loading),” Patterson said, “confirming this as the mechanism through which the unloading shoes achieved their clinical effects.” He added, “This is the first evidence of a potential subgroup of knee OA patients that are more likely to respond to biomechanical interventions designed to reduce knee joint loading, such as unloading shoes.”

Tips for choosing the correct shoe

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Andy Gerken, MD, foot and ankle specialist with Hoag Orthopedic Institute, Newport Beach, CA, noted that athletic shoes are the easiest to work with in terms of foot function when trying to reduce pain. “A rigid insole to prevent bending stresses that exacerbate midfoot and forefoot arthritis is helpful,” he said.  For runners, particularly older runners (older than 35 years), he recommends a running shoe that takes shock while allowing normal running kinematics and gait.

Kevin D. Plancher, MD, MPH, clinical professor of orthopaedics at Albert Einstein College of Medicine in Bronx, NY, said running is an important sport and 1 shoe does not fit all, especially when considering differences between men and women runners. Women’s running shoes tend to have a narrower heel and a wider forefoot, with greater flexibility, he said, with the front of the shoe offering a wider toe box, so the toes are not squeezed. “They are lighter in weight with deeper grooves. If your foot gets flat and the arch collapses, it puts pressure on the inside of your knee. We have to put something in the sneaker or create a good platform to take pressure off.”

Minimalist shoes have been tested in various contexts for knee OA and appear to have an important role in reducing loading through the medial compartment in people that have medial tibiofemoral OA. However, Hunter said, it’s been difficult to translate that into clinically important outcomes such as pain and function.  “People should be willing to spend a lot of time trying on different shoes in order to discover the pair that works best,” he said. This is particularly true for people with pre-existing foot problems or who are overweight or obese. “They should be careful not to use flimsy, stylistic shoes that look good but can result in problems later.”

Keith Lorria is a freelance medical writer.

REFERENCES
  1. Hinman RS, Wrigley TV, Metcalf BR, et al. Unloading shoes for self-management of knee osteoarthritis: a randomized trial. Ann Intern Med. 2016;165:381-389.
  2. Chugthai M, Newman JM, Akil S, et al. Knee pain and the use of various types of footwear: a review [published online February 8, 2018]. J Knee Surg; doi: 10.1055/s-0038-1626735.
  3. Paterson KL, Kasza J, Bennell KL, et al. Moderators and mediators of effects of unloading shoes on knee pain in people with knee osteoarthritis: an exploratory analysis of the SHARK randomized controlled trial. Osteoarthritis Cartilage. 2018;26:227-235.
  4. Paterson KL, Bennell KL, Wrigley TV, et al. Effects of footwear on the knee adduction moment in medial knee osteoarthritis: classification criteria for flat flexible vs stable supportive shoes. Osteoarthritis Cartilage. 2017;25:234-241.
  5. Paterson KL, Kasza J, Hunter DJ, et al. The relationship between foot and ankle symptoms and risk of developing knee osteoarthritis: data from the Osteoarthritis Initiative. Osteoarthritis Cartilage. 2017;25:639-646.
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