Winter Sports Medicine and the Podiatrist 99 Alpine and Cross Country Skiing and Snowboarding Are All Sports with Which DPM’S Should Be Familiar

BIOMECHANICS

Winter Sports Medicine and the Podiatrist 99 Alpine and Cross Country Skiing and Snowboarding are all sports with which DPM’s should be familiar.

By Jeffrey A. Ross, DPM, MD

or DPM’s, alpine skiing, nique, or performance problems relat- Whatever the reason, you may be the cross-country skiing, and ed to foot or boot-fit discomfort. One skier’s last hope after attempting to snowboarding have become must understand the concepts of lower correct the situation first at the ski another area where podiat- extremity biomechanics related to ski- shop or with the boot fitter. ric lower extremity expertise Fcan be focused. The sports podiatrist can become involved at a variety of The skier can be a very challenging patient. levels. Understanding the individual sports, knowing their biomechanics, as well as the patient’s special needs, can enhance your overall sports prac- ing, boot design, boot fitting, as well as Alpine Skiing Biomechanics tice. Many skiers and boarders who the relation between a ski orthotic and Alpine or downhill skiing is a might not find the answers at the ski the boot in which it sits. complex skill that requires controlled shop will look to you for the right Unlike the average runner who pronation, setting the foot, ankle, and solutions. Whether it’s for canting has a small bag of running shoes, lower extremity on the inside edge. boots and skis or prescribing and fab- the skier who makes the trip to your Pronation sets the inside edge of the ricating footbeds and orthoses, you office has a big bag filled with ski downhill (control) ski and allows for can help to prevent injuries and pro- boots, as well as foot beds and or- the skier to lean inward against the ski, vide more comfort for your patients thotics. The skier’s visit to your office which holds a skid-less arc throughout during their winter exercise season. may be because of chronic foot pain the turn. While balanced on a beam of The skier can be a very challenging due to the boots, or his/her perfor- flexible composite (6.3 cm wide), the patient. Be aware of his/her numerous mance being affected by the inability skier drives the shin forward against concerns, whether due to biomechani- to be totally comfortable in the boot the stiff boot cuff and swings the hips cal imbalances leading to poor ski tech- while initiating and completing turns. PhotoDisc Continued on page 100

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Winter Sports (from page 99) pinated subtalar joint) by prescribing a Ski Fitters and DPM’s variety of orthotics for control in their The foot specialist or sports med- to the opposite direction. The ski rolls ski boots. icine specialist should have a basic onto its sharp steel edge and bites the For many years custom insoles understanding of the ski boot de- snow, creating an arc across the hill (molded to the foot in the ski shop) sign (just like an understanding of (Ross & Subotnick, 1999). Skiing is have been effective for mild foot and the running shoe), as well as skiing analogous to ballet on snow, where the lower leg imbalances, particularly biomechanics and performance. You skier encounters many centrifugal as well as g-forces during the turns, while simultaneously attempting to keep the center of gravity in line over the center You should know the sport before you of the ski. Any change in the normal treat the athlete. biomechanical balance can alter the skier’s ability to develop a controlled turn, thus predisposing the skier to injury if the abnormality is signifi- cant enough. Variable factors, such as structural biomechanical deformity, functional deformity or dynamic imbalance of 100 muscle groups can also have an influence on a skier’s performance, and help predict poten- tial injury. Skiers who have biomechanical Figure 1: Ski boot that is reversible: after removing the shell, it can become a Figure 2: Solomon ski boot overlapping abnormalities will com- snowboard boot with upper buckle posterior pensate by obtaining pronatory forces from other joints, for exam- ple, the hips and knees, in order to ski effec- tively. Using the Elec- tro-Dynogram (EDG), Ross (1985) showed that forces are transmitted from both the forefoot and the rearfoot, which the skier utilizes in up-and down-weight- ing, as well as in the completion of turns. Figure 3: Technica traditional ski boot Figure 4: Snowboard boots (harder shell and softer shell) on Abnormalities which with upper buckles anterior snowboard were observed includ- ed: excessive foot pronation, shortened for the overpronator skier (Figure 6). should know the sport before you heel contact with excessive propulsive However, for the more severe rearfoot treat the athlete. It is essential for the phase on the toes, extreme forward and forefoot abnormalities, prescrip- foot specialist to establish a work- lean of the boot, as well as asymme- tion orthoses can be a valuable way ing relationship with the boot shop, try between the two feet. These com- to provide proper foot bed balance, as well as the ski boot fitter (Figure bined affected the skier’s effectiveness and to improve ski performance and 9). These individuals have a working and overall performance. The sports efficiency (Ross & Cohn, 1984). Boots understanding of basic biomechanics medicine podiatrist can assist skiers to today typically will have easy-to-cus- in relation to boot performance, fit, overcome some of these lower extrem- tomize liners and removable full- and comfort; but they also understand ity abnormalities, including poor skiing length soft support systems within their own limitations in addressing the style, poor edge control, as well as foot the inner boot. The pre-existing insole more challenging foot and lower leg imbalances (e.g., rearfoot varus/valgus, may be substituted with a custom in- problems and they generally prefer to forefoot varus/valgus, pronated or su- sole or prescription orthotic. Continued on page 102

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Winter Sports (from page 100)

have experts assist them in diagnosis and treatment. This relationship can prove to be extremely satisfying and rewarding. The foot specialist can aid in the selection process for the “right boot” (similar to helping to choose the right running shoe) (Figures 2, 3). Podiatrists help to determine the foot type, biomechanical weakness and areas of weakness and stress. DPM’s diagnose bony deformities, biomechanical imbalances, areas of the foot where the boot might cause friction and irritation, as well as those skiers who may suffer from circula- tory impairment, nerve entrapment, and metabolic disorders. With this information, a ski boot fitter can then determine if the skier needs a boot designed for a flat or high arched foot, a narrow or wide foot, a boot with high 102 volume, a pure forward entry boot, or possibly a hybrid (with both overlap and rear entry design), or a boot with a narrow heel pocket.

Tibial Varum Figure 5: (Left) Uncompensated Tibia Vara in the Ski Boot: The boot cuff does not compensate ade- Tibial varum is one of the more quately for the tibia vara, predisposing the skier to ride on the outside ski edge. common lower extremity biomechanical abnormalities that can have a (Right) Tibia Vara—Measurement: The skier is standing on the baseboard of the boot with the liner negative impact on a skier’s perfor- removed, and has assumed the functional skiing position. The cuff can then be aligned to the longi- mance. Tibial varum is a result of tudinal axis of the lower leg. Note that if the skier uses a footbed or corrective orthotic, the device an uncompensated varus deformity must be placed on the baseboard of the boot before correction of the tibia, which transmits instan- taneously to the ski-snow interface, and causes the skier to ride exces- By keeping the orthotic as thin as possible, there will be sively on the outside edge of the ski. Those skiers who have greater than more volume for the foot and toes to function. 8 to 10 degrees of tibial varum will have a great deal of difficulty initiating a parallel turn without “catching” other foot and lower leg abnormal- to the front-entry and hybrid-designed the outside edge of the ski (Figure 5). ities that can contribute to a skier’s performance boots. Ski boots have difficulty in both edge control and evolved biomechanically, as well, of- Boot Technology performance. These include genu fering adjustable features, such as: Boot technology has improved so valgum, subtalar varus, forefoot val- internal or external canting systems, that high performance boots provide gum, transverse plane asymmetry, as adjustable “spoilers” or shaft angle a boot cuff adjustment to accom- well as leg length discrepancies. adjustments, boot flex, forward lean, modate for varying degrees of tibial The common complaint that boot internal/external heaters and custom varum and help to create a flat ski fitters and foot specialists hear is, “my heat-moldable liners made of ethyl-vi- surface. One of the simplest ways of feet hurt in my boots!” In addition, nyl acetate (EVA). treating high degrees of tibial varum skiers often complain that their feet DPM’s should be aware that the in the skier is to use a full-length, are tight, that they are cold, and that ski boot removable foot bed may be canted orthotic within the boot. The they experience friction, irritation, and replaced with custom-made orthoses. reason for its success is that you are blisters. As we have seen, techno- Many of these devices are made in providing total foot contact within logical development of the ski boot the ski shop with a computer imprint the boot, correcting biomechanical has gone from a traditional overlap of the skier, or by placing the foot foot imbalances within the foot and design to a skier-friendly rear-entry in a semi-weight-bearing neutral po- lower leg. There are a number of design. Now they have returned back Continued on page 104

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Winter Sports (from page 102) to as a swing kick and glide. Lon- ger ski poles are used to create sition, with a knee stabilizer ap- upper body stability and propul- paratus built into the platform to sion, while the heel is kicked up- accurately align the knee over the ward to maintain forward motion foot for a more complete lower with a forefoot propulsion on the leg correction. In the tradition- ski. When alternating the oppo- al method of making an in-boot site arm, this creates a diagonal cast, the skier assumes a neutral stride and leg forward movement, ski stance position, which will similar to walking or running. help achieve a greater degree of The difference between the alpine correction. It has been shown that boot and the cross-country boot is controlling excessive pronation/ that the trekking boot is a hybrid supination and locking the mid- between the backcountry and a tarsal joint (stability) will greatly running racing flat in both design enhance edging and performance. Figure 9: Custom boot fitter Bob, a Pedorthist, checking the and support. In comparison, the If you’re looking to tinker with boot and bindings for proper release cross-country boot has much more boots, I strongly suggest that you freedom of movement, while giv- go to the shop, and spend a weekend the sport and thus have never dis- ing up some of the support that the in the tech’s shop learning about the covered its incredible aerobic as well alpine provides. In cross-country ski- various components and complexities as muscle-strengthening advantages ing, sagittal plane motion is the pre- of the ski boot (Figures 7, 8). The over alpine skiing. To begin with, the dominant direction of the foot and leg boot fitter/tech will be very willing technique for cross-country skiing is and it is not essential that the touring 104 to share information with you, while entirely different. In downhill skiing, skier require stability in the shoe for attempting to pick your brain at the the heel and lower leg are locked in a exaggerated turns. Typically, the tour- same time. The five areas of concern rigid boot, allowing for more control to ing skier will be in a track on a course, in the foot bed are: zone one—the the skier’s rearfoot, while the body’s except when skiing backcountry. foot bed, zone two—the tongue, zone center of mass is located directly over Biomechanical considerations are three—the hindfoot, zone four—the the subtalar joint. This provides for just as important as in alpine ski- shaft, and zone five—the forefoot. compression forces to be properly ing. The patella should be properly aligned, while maintaining rearfoot aligned over the skis in a bent-knee Cross-Country Skiing neutrality. Comparatively, cross-coun- skiing position. For the touring skier, Most sports medicine podiatrists try skiing involves a heel that is re- a lighter weight, more flexible orthot- are familiar with alpine skiing, but peatedly lifted within the shoe from ic would be preferred for this type of when it comes to cross-country ski- the ski surface and lowered again. boot. By keeping the orthotic as thin ing, it’s like speaking a foreign lan- This creates a more unstable situation as possible, there will be more vol- guage. That is probably because many for the skier. The technique that is ume for the foot and toes to function. people have never even attempted used in cross-country skiing is referred Continued on page 105

Figure 6: Measuring device for heating and cus- Figure 7: Heating machine to expand the outer Figure 8: Heating machine to soften the inner tom fitting OTC (Superfeet) insole shell for custom fitting boot to custom fit to the foot

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The AAPSM: the Heart and Soul of Sports Podiatry

he American Academy of Podiatric Sports Med- • Exclusive discounts on all AAPSM sponsored Ticine serves to advance the understanding, pre- meetings vention and management of lower extremity sports • Opportunities to serve on various AAPSM and fitness injuries. The AAPSM believes that provid- Committees/Executive Board ing such knowledge to the profession and the public • Fellowship Journal Article Review will optimize enjoyment and safe participation in • Grant funds available for research, fellow- sports and fitness activities. Their aim is to accomplish ships, teaching this mission through professional education, scientific • Members recognized as sports medicine ex- research, public awareness and membership support. perts with media One of the unique benefits of membership in the • Nationwide referral system for not only AAPSM is their series of live cadaver videos covering media but the general public the following topics: • Collaborative efforts with members of the • Achilles Surgery Joint Commission on Sports Medicine and Science • Percutaneous Achilles Repair (Fit Feet, Athletes in the Arts, etc.) • Lateral ankle surgery • Networking opportunities • Percutaneous Fibular fracture repair • Monthly AAPSM e-newsletter blast with op- • 1st MPJ anatomy portunity to publish information, publicize accom- • 2nd MPJ Plantar Plate repair plishments (Members in the News) 105 • Medial Arch/PTD repair • Speaking opportunities at various school • Select Lectures from 2015 Stand Alone meetings • PRP Update • Opportunity to print various sports medi- • Liability in Sports Medicine Webinar cine-related brochures for office distribution • Access to sports medicine-related power And the cadaver video series is of course just point presentations one of many benefits of membership. The long list For questions on membership benefits or includes: any other aspects of the AAPSM, please • Shoe discounts offered from various footwear contact Executive Director Rita Yates at companies [email protected]. •

Winter Sports (from page 104) to the nature of the short pivoting Ross, J.A., Subotnick S.I: Alpine Ski- turns. An evolution has also taken ing In: Subotnick SI (ed.) Sports Medicine Snowboarding place in boots (Figures 1, 4). Earlier of the Lower Extremity, 2nd ed. Edin- Snowboarding has become the designs produced a soft boot with burgh: Churchill Livingstone, pp. 671-686, 1999. mountain rave. A winter version more freedom of movement, where- Ross, J.A., Cohn S.;If the Boot Fits, as more recently a full hard shell of skateboarding, or surfing, snow- You Probably Have a Custom Insole, Ski boarding has its risks just as alpine and half shell are typically worn. Magazine, October, 1984. skiing does. The incidence of in- The softer design, allowing for more Ganong RB, Heneveld EH, Bernanek juries between the upper extrem- foot motion, also resulted in more SR, Fry P; Snowboarding Injuries: A Re- ity (44%) compared to the lower injuries than the harder designs. port on 415 patients. The Physician and extremity (43%) is nearly equal. The most common injury site with Sports Medicine 20:114, 1992. The most common site of injury the soft boot was the ankle, while is the wrist, followed by the knee, the rigid, full-shell boots protect the Jeffrey A. Ross, DPM, and then the ankle (Ganong, et al., ankle, but allow for more forces to MD is Assistant Clinical 1992). The difference between al- be transmitted to the knees. As a Professor at Baylor Col- pine skiing and snowboarding is that result, more knee injuries have been lege of Medicine and the “boarder” lacks the freedom of reported due to this change in shell Chief of the Diabetic Foot Clinic at Ben Taub individual leg movement, thus de- design. PM Hospital. He is past creasing the chance for recovery. Note: Excerpts taken from Ross, J.A.: president of the Ameri- Whereas alpine skiing incorporates Sports Medicine and Injuries in Neale’s can Academy of Podiat- the integration of the foot, knee, and Foot Disorders Diagnosis and Manage- ric Sports Medicine and hip motion, snowboarding focuses ment, Sixth Edition, Churchill Livingstone, a marathoner, triathlete, former ski patroller energy on the hips and knees, due London, Pages 329-331, 2002. and racer, and contributor to Ski Magazine. www.podiatrym.com SEPTEMBER 2018 | PODIATRY MANAGEMENT 9705 MEN'S NEW KNITTED9705 MEN'S WALKING NEW KNITTED9705 MEN'S WALKING NEW KNITTED WALKING

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