Orthotics (Insoles) for Plantar Fasciitis
Before we start, I just need to clarify the nomenclature pertaining to those weird and wonderful objects people put in their shoes. Most of you know them as insoles or orthotics. To be pedantic, the use of the word orthotics to describe the objects one places in their shoes is incorrect. The term Orthotics actually refers to the branch of medicine that deals with the provision and use of artificial devices such as splints, orthoses, and braces. The correct term for the insoles some of us wear in our shoes is orthoses (I did warn you I was being pedantic!). However, hardly anyone uses the correct term, not even most podiatrists, and come to think of it, not even me (at least not consistently). Therefore for the rest of this article I shall use the term orthotics synonymously with insoles. Well that felt good to get off my chest and should hopefully prevent a few podiatry boffins from correcting me on my terminology.
So, orthotics, what are they? They are medical devices that you wear in your shoes, often to change your foot function and the forces acting upon your feet and perhaps most importantly, to help with pain. Orthotics come in many different shapes and sizes. You can buy them pre-made out of a box or you can have them custom made. There are thousands of different designs on the market. Some are made well from high quality materials and some are completely rubbish. Most of my patients I see in clinic have usually tried something pre-made prior to seeing me, sometimes good, sometimes a complete waste of money. This article provides a brief overview the thinking behind the use of orthotics, the current evidence to prove/disprove their effectiveness along with my own personal opinion.
Rationale for orthotics
The most common cause cited in the medical literature for plantar fasciitis is excessive biomechanical stress of the plantar fascia, particularly at its attachment to the medial calcaneal tuberosity (heel bone). The main job role of the plantar fascia is to support the arch of the foot. The aim of orthotics is to reduce the biomechanical stress placed on the plantar fascia by supporting the arch of the foot. Therefore it is no surprise that orthotics are amongst the most commonly reported treatment methods for plantar fasciitis. There are thousands of different designs of orthotics, which are made from different materials and come in all different shapes and sizes. This makes it incredibly difficult to determine whether orthotics are any good for treating plantar fasciitis due to the multitude of variables. nonetheless, let's take a look at some studies.
Do they work? Where is the Evidence?
Campbell and Inman in 1974, were the first authors to describe success with mechanical therapy orthotics. They treated 33 patients and retrospectively reported a 94% success rate. Another study by O’Brien and Martin, in 1985, performed a retrospective telephone survey of 41 patients with 58 painful heels. Excellent and good results were recorded for 96.7% of the patients, most of whom received multiple therapies. Subjectively, the patients stated that orthotics were the most successful treatment modality. It is noted that the two mentioned studies above are very dated and of poor quality. We therefore, have to take the findings of these studies with a large pinch of salt.
A more recently published study by Lynch et al (1998) concluded that mechanical control of the foot via orthotics was more effective than anti-inflammatory therapy or accommodative therapy in the conservative treatment of plantar fasciitis. The Roos et al (2006) study (referenced previously in the night splints article) demonstrated that orthotics were effective for both short term and long term management of plantar fasciitis. This was a robust, good quality study.
A randomised control trial (high-quality study) was conducted by Landorf and colleagues (2006). They compared 3 groups:
Group 1 custom made orthotic
Group 2 prefabricated orthotics
Group 3 Sham (fake) orthotics
Their findings were that foot orthotics produced small short-term benefits in function and small reductions in pain for people with plantar fasciitis. But they did not have long-term beneficial effects compared with a sham (fake) device, meaning that at a 12-month review the foot orthotics were no better than a fake insole, essentially no treatment at all. There was no significant difference in effectiveness between the custom made orthotics and the prefabricated orthotics. So the small short-term pain relief seen in the two groups who had orthotics were very similar.
The most recent study published compared 60 participants with plantar fasciitis diagnosed with an ultrasound machine into 3 groups:
custom orthotics and new shoes
sham (fake) orthotics and new shoes
sham (fake) orthotics and patients regular shoes
There were 20 participants in each group. The researchers found that custom orthotics in new shoes improved pain and reduced plantar fascia thickness over a period of 12 weeks compared to new shoes alone or a sham orthotic (Bishop et al 2018).
A cadaveric study (using donor's feet) was published by Kogler and colleagues (1995) to test the theory that orthotics do indeed support the arch of the foot as they are believed to. They measured the level of strain on the plantar fascia using an electromechanical test machine and applied a load to the foot whilst barefoot, in shoes and in different types of orthotics. They found that some of the orthotics (ones with better anti-pronation support) significantly reduced strain in the plantar fascia tissue compared with the barefoot condition. These study findings support the theory behind prescribing orthotics to reduce strain on the plantar fascia in the treatment of plantar fasciitis.
Finally, the American Physical Therapy Association (APTA) published clinical practice guidelines for plantar fasciitis. They graded the overall evidence strength of different treatments ranging from A (highest strength) to F (lowest strength). Orthotics were graded as an A (APTA 2014).
Custom made or prefabricated?
This is a hotly debated topic in the podiatry profession with very mixed opinions coming from different experts. If we look at the evidence alone, it would appear that custom orthotics provide not added benefit over prefabricated orthotics, however, anecdotally I have prescribed hundreds of prefabricated orthotics as well as custom made orthotics for treating plantar fasciitis. My personal preference is custom made and no, not because of the £££s, but because I feel I have more control over what I can achieve from the orthotic. With a custom made device I am able to take a scan or cast of the patients foot in the desired position. As the orthotic made based on the shape of the scan/cast I am confident the orthotics will interact with the feet in a way that will maximise the chances of them working. When using a prefabricated orthotic, one has less control in this regard and has to hope that the shape of the orthotic is compatible with that individuals feet. In addition to this, I am able to carefully select the materials I want the orthotics to be made from and this varies based on my patients individual characteristics. Over the years I have been practising, I can honestly say I have seen more consistent and better treatment response from custom made orthotics over prefabricated orthotics. In hindsight, I wish I had audited this as then I would have some proof of my experience, alas I do not.
The use of orthotics is generally a very safe treatment option and is commonly prescribed to help with a large array of musculoskeletal conditions including plantar fasciitis. A small percentage of people experience adverse effects from wearing orthotics which may include blistering of the skin on the sole of the foot, aches and pains in other joints such as knee, hips and lower back. Most of these aches and pains subside once you become used to your orthotics which usually takes approximately 1-2 weeks. Wearing orthotics should not cause acute pain. If you experience pain as a result of wearing orthotics you should stop wearing them immediately and seek advice from a podiatrist.
Orthotics play an important role in the multi-faceted approach to treating plantar fasciitis. Like stretching exercises, orthotics help address and reduce the mechanical stress that leads to injury of the plantar fascia as has been proven in cadaveric studies. There is a fair level of high-quality evidence to prove their efficacy in the treatment of plantar fasciitis both in short and long term and are therefore considered an evidence-based treatment option.
Thanks for reading. Comments welcome.