A clinical guide for shoe assessment of patients
Since footwear can hugely affect posture & biomechanics, a clinical shoe assessment of a patient is very important. An ‘incorrect’ pair of shoes can lead to several injuries, even if there is no physical limitation in the body.
The term ‘incorrect’, defines a shoe that is NOT suitable to the structure & function of the patient’s feet. Moreover, this term can also refer to shoes that can no longer assist the foot because of being damaged or worn out.
SHOE ASSESSMENT: REPLACEMENT GUIDELINES
(For this blog, we will restrict ourselves to running & walking shoe assessment as it is a very active area of research.)
Running shoes tend to lose between 30% and 50% of their shock absorption after about 250 miles of use. Even if not worn frequently, the shock-absorbing capability of shoes gets significantly reduced after 1 to 2 years. (Asplund & Brown, 2005)
Hence, shoes with excessive wear & tear can not only reduce performance but also increase the risk for injuries. This wear and tear can be evaluated in terms of the amount of usage, signs of wear, and age of the shoe.
Studies by (Asplund & Brown, 2005) (Furman, n.d.), have discussed guidelines on shoe replacement. Some of these are mentioned below:
- After 300-500 miles of running or walking.
- Within 1 year of use, whether the shoe is worn out or not.
- Any signs of unevenness in the midsole, when placed on a flat surface.
- Any noticeable creasing in the Midsole.
- If the heel counter appears flexible when compressed from side to side
- If the heel counter appears deviated to one side when viewing from the rear of the shoe
- When the outer sole has worn through to midsole or there is more than 4mm difference between the medial & lateral side of the heel.
SHOE ASSESSMENT: PRESCRIPTION PROCESS
Since all feet are unique, there is a set of guidelines recommended by the American Academy of Podiatric Sports medicine (AAPSM) that can be helpful in shoe assessment & prescription.
As per Stephen M. Pribut, ex-president of AAPSM, a shoe prescription should be done keeping the following factors in mind. Although these factors are extremely relevant for running shoes, they should kept in mind while recommending walking shoes too.
- Biomechanical Needs
- Past experience with shoes
- Current Problems
- Environmental Factors
- Running & Racing Requirements
To address all these needs of the patient, a comprehensive examination of the foot & current footwear is necessary. In this blog, we will be discussing certain important factors that should be assessed in these examinations.
FOOT SIZE & SHOE FIT
Foot length vs shoe length
It’s important to ensure that the shoe is as per the length of the foot. Measurement of foot length should not only be limited to the overall length (heel to toe measurement), but also arch length (heel to ﬁrst metatarsal head) measurement.
Shoes are designed to ﬂex at the ‘ball’ of the foot. Therefore, the ﬁrst metatarsal joint should be positioned in the widest part of the shoe. This provides room for the toes so they are not conﬁned. Besides, an adequate lacing system or adjustable strap is also helpful in obtaining a required fit. (McWhorter, et al., 2003)
As a general rule, having a thumb’s width in space beyond the end of the longest toe to the tip of the shoe ensures a good fit. (Langone, 2010)
Foot length & width measurement
In addition to foot length, foot width is another factor that is often neglected during shoe assessment. Both foot length & foot width can be easily measured using a Brannock® device. (Buldt & Menz, 2018)
Although awareness is increasing, many patients are still unaware of the need for wider shoes to address foot deformities like bunions or hammertoes.
However, a positive trend in athletic shoes over recent years has been the availability of various width options. Brands like New Balance, Asics, Orthofeet offer a full range of narrow, medium & wide widths to help patients with foot width related issues.
- Adequate depth over joints & toes is important to allow free movement. This is particularly important at toe taper to eliminate pressure over the dorsal deformity aspect of the toes and nails
- Feet are not perfect matches. One foot is always a little bigger than the other. In such cases, it’s always good to fit the shoe to the larger foot.
- As studied by (McWhorter, et al., 2003), the volume of the foot increases by 3% after 10 minutes of light running on a treadmill. Hence, it is important to take measurements after exercise.
A shoe with a firm heel counter
Stiffness in the heel counter is necessary to provide additional support & control excessive eversion-inversion of the foot.
A study by (Stacoff, et al., 1992;) on the role of heel counters discovered that the heel inside the shoe moves lesser and slower than the heel counter itself. Hence, we can comment that the heel counter acts as a protection for the rear foot.
This parameter is a part of the three-point testing methodology for athletic shoe assessment, recommended by the American Academy of Podiatric Sports Medicine.
To test the heel counter, grip the medial and lateral aspects of the heel counter of the shoe and try to squeeze it (Richie Jr., 2008). A good heel counter will be stiff and resist any deformation. If the heel counter deforms easily, it is not likely to offer a high degree of rearfoot support.
The stiffness of the heel counter may also depend upon the particular activity for which the shoe was designed. For athletes playing a sport that requires a lot of lateral motion, a shoe with a flexible heel counter might be desirable.
As suggested above, this decision should be based on the needs of the person.
A shoe with good torsion control
Like a firm heel counter, a shoe that is resistive to torsion and twisting is capable of providing better stability & motion control.
If the foot is very flexible in the frontal plane (meaning that there is a lot of inversion and eversion occurring), the torsional stiffness of the shoe is important (Levine, 2010). This controls any excessive motion and reduces the chances of injury. Plantar heel pain syndrome is associated with shoes with poor torsional rigidity. (Richie Jr., 2008)
To test the torsional rigidity of a shoe, hold the heel and the forefoot portions of the shoe in both hands. Now, twist the shoe in the frontal plane into inversion/eversion. (Richie Jr., 2008) A shoe with poor torsional rigidity will offer minimal or no resistance to this twisting motion.
Good torsional rigidity is often beneficial in road running or running on flat surfaces. However, some sports require a lot of lateral cutting along with the forward motion. In such cases, a shoe with minimal torsional stiffness may be desirable.
For example, during trail running, the foot is placed in very different positions due to varying terrain or while doing lateral movements. Hence, the shoe should allow the foot to pronate and supinate as needed in response to these positioning stresses. (Williams, 2010)
FOREFOOT FLEXIBILITY & MIDFOOT STABILITY
This parameter is probably the most important factor in athletic shoe assessment. Like heel counter stiffness and torsion control, it is also a part of the three-point testing methodology by AAPSM.
The test evaluates the ease of flexion of the most distal third of the shoe as well as the flexion resistance of the middle third of the shoe. (Williams, 2010)
A shoe with good forefoot flexibility
To determine this characteristic, simply hold the heel and press toe of the shoe against a hard surface. Ideally, the flex point of the shoe should correspond to the flex point of the foot i.e. around the ball of the foot. (Richie Jr., 2008).
This allows the foot and the shoe to function as one unit. A shoe that does not exhibit this behavior, will alter the normal function of the foot.
A shoe with poor midfoot stability
To test the midfoot stability of a shoe, simply bend the shoe between your hands. Any excessive flexion is an indicator of poor midfoot stability. Shoes that bend at the midfoot instead of forefoot should not be recommended to patients.
Such shoes increase the compression in the midfoot area, leading to prolonged pronation at Midstance during gait (Williams, 2010). This can trigger significant compensations within the foot or other aspects of the lower extremity. Hence, midfoot stability is necessary for running & walking footwear.
ASSESSMENT OF SHOE WEAR PATTERN
Pressure under the sole of the shoe should generally be even, with no excessive wear in any particular region. Additionally, normal wear should occur at the lateral heel (where your foot first hits when you walk) and medial central forefoot (where you push off when you step).
A shoe with normal wear pattern
An overpronated/low arch foot shows wear on the medial edges of the heel & the balls of the feet.
The wear is present at the lateral side of the feet in case of high arched patients.
There is another simple method to understand the correlation between foot alignment and sole wear pattern( Asplund & Brown, 2005). It is a simple test that involves placing the shoes on a level surface and observing the heels for tilt. An excessive medial tilt indicates overpronation, and an excessive lateral tilt signifies underpronation.
A lot of clinics also use gait analysis or posture analysis to analyze foot alignment and its effect on lower body biomechanics. This is also helpful in pre-post comparisons to understand the effects of the interventions on the gait of the patient.
All that is required to get started is a video camera/smartphone along with a video analysis software.
ADDITIONAL WEAR PATTERNS (Williams, 2007)
- The absence of wear at the tip of the sole of an old and worn shoe may indicate a lack of push-off during the gait cycle.
- Excessive forefoot wear indicates ankle joint equinus
- Circular forefoot wear over the first metatarsophalangeal joint is present in pes cavus deformity.
MIDSOLE DENSITY VARIATIONS
The midsole is one of the most important components in the shoe. Any material variations in the midsole directly affect the stability & cushioning experienced by the foot.
Providing cushioning on the medial side of the midsole is generally useful in patients with a high arch foot. In such cases, the cushioning on the medial side promotes a greater degree of rearfoot eversion. Such midsoles are often found in ‘Cushioned’ shoes, which are designed to promote more pronation.
On the other hand, a firm midsole on the medial side is generally useful in patients with a low arch or an overpronated foot. In such cases, the stiffness on the medial side reduces the tendency of pronation. Such midsoles are often found in ‘Motion control’ shoes, which are designed to control excessive pronation.
Patients with a normal-arch function with an appropriate amount of pronation and do not require additional medial support or excessive cushioning in the midsole. (Werd & Knight, 2010)
ASSESSMENT OF SHOE LAST
The last describes the shape of the shoe. Generally, there are three kinds of lasts.
Straight-last: More resistant to pronation, heavier, & often incorporate a controlling medial post.
These are found almost exclusively in motion-control shoes.
Semi curved last: Intermediate between straight lasted and curve-lasted.
These are found in most running shoes
Curve-last: Lighter, more cushioned, & offer minimal resistance to pronation.
These are commonly found in competition shoes, cushioned, and neutral shoes
TYPES OF RUNNING SHOES (Langone, 2010)
Neutral shoes: These shoes provide a blend of cushioning, medial support, and durability. Semi curved last (to offer hindfoot stability and forefoot flexibility). They often have a medial post or multi-density midsole to provide a degree of pronation control. Well suited to the midweight runners & people with neutral pronation and medium-to-low arches.
Motion Control Shoes: These shoes provide the maximum pronation resistance, stiff heel counter, high torsion resistance, stiff medial midsole, rigid medial post & Straight last. Benefit heavyweight runners or runners with a low arch or an overpronated foot.
Cushioned shoes High Arch / Supinated foot: These shoes provide the minimal pronation resistance, higher flexibility, soft & cushioned midsole, least medial support & curved last. Benefit light to midweight runners & runners with High Arch / Supinated foot
SOME SPECIFIC PROBLEMS THAT INFLUENCE SHOE ASSESSMENT
As we discussed above, previous injury history can hugely affect the process of shoe assessment & prescription.
For eg, patients with previous stress fractures benefit from greater cushioning in the shoes. On the other hand, a runner with a history of Achilles tendinopathy may require a shoe with firm midsoles and ample heel elevation. (Richie Jr., 2008)
It is important to keep following up with patients and take their feedback. A lot of clinicians use video gait analysis to quantify the changes in the walking or running pattern due to the footwear.
Needless to say, a detailed injury history & physical examination of the patient are extremely helpful in effective shoe recommendation.
In conclusion, a new shoe is a big biomechanical change introduced in the body. Hence, shoe assessment and prescription should be an informed decision done by considering all factors into account.
ABOUT THE AUTHOR
With over 4 years of experience in biomechanical analysis, Siddharth is the product manager of GaitON. He has been certified in the courses of ‘Running Mechanics for clinicians’, ‘Common biomechanical errors seen in runners’, ‘Rehabilitation of running biomechanics’.
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