Preventing Common Foot Injuries

author : AMSSM

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What foot injuries are common in triathletes, and how can I prevent the serious ones?

Member Question:

"I am new to triathlon and have read about a lot of triathletes suffering from foot pain. What are the kinds of foot pain and injuries common in triathletes, and is there anything I can do to prevent it from happening to me?"

Answer from Troy Smurawa, M.D.
Member AMSSM

Injuries of the foot are common among runners of all levels of competitiveness from the recreational runner to the competitive elite runner. Most of these injuries are mild and self-limiting responding to rest and rehabilitation, but it is not uncommon to develop a more serious injury that may pose significant long term consequences.

Changes in training regimen, biomechanics and running shoe often contribute to the development of foot running injuries. The recent popularity of barefoot running and minimalist running shoes may play a role in foot injuries in runners who do not properly condition or adapt their running mechanics appropriately. I will describe the more common running foot injuries and discuss contributing risk factors as well as treatments and corrections for prevention.

The Forefoot

The foot, particularly the forefoot, serves two primary functions in running. First, it serves as a rigid platform for weight-bearing during running. Second, it functions as a mobile platform to accommodate for the changing surface of the ground while running. This platform is made up of the tarsal, metatarsal, and phalanges bones of the foot and supported by the surrounding soft tissue structures. Injuries to these structures often occur as a combination of the repetitive stress of running with some form of biomechanical alterations in running gait. These injuries include but are not limited to stress fractures, tendinopathies and neuropathies.

The Role of the Sesamoids

Embedded within the flexor hallucis brevis tendon of the great toe are two round bones called sesamoids. These bones play an important role in the function of the flexor hallucis brevis tendon which functionally lengthens the great toe during the late stance phase of the gait cycle. It enables a smooth lateral to medial weight transfer throughout the foot. The tibial or medial sesamoid is larger and bears a greater weight load and therefore at a higher risk of injury.

The types of sesamoid injuries include, in order of prevalence, stress fractures, sesmoiditis, acute fracture, osteochondritis, osteoarthritis and bursitis. Of clinical significance, it is found that 5-35% of the population has a bipartite or multipartite sesamoid that may be mistaken for a fracture. Runners with a sesamoid injury will present with plantar medial forefoot pain with weight-bearing. On examination there is localized tenderness and often swelling. Passive dorsiflexion of the great toe will elicit pain and resisted plantar flexion will demonstrate weakness and pain.

X-rays of the foot with a special sesamoid view are typically normal but may demonstrate a fracture, malalignment or degenerative changes. A bone scan or MRI is often necessary for a definitive diagnosis. Treatment involves unloading the first metatarsal phalangeal joint by restricting weight-bearing activities and using a sesamoid relief pad or an orthotic with a cutout.

For difficult cases, a period of nonweight-bearing and immobilization is necessary. Early detection of a sesamoid stress fracture is extremely important since a minimum of 6 weeks of nonweight-bearing is required to prevent the risk of a fracture. Those that fail conservative treatment may require surgical removal but this often leads to long term biomechanical consequences.

The metatarsals

Metatarsal stress fractures are the second most common stress fractures in runners and the most common stress fracture in the foot. During running, the plantar musculature of the toes dissipates the stress on the metatarsals. Increased stress on the metatarsals occurs when muscles fatigue during prolonged running. The second, third and fourth metatarsals account for 90 percent of the stress fractures. The second metatarsal is more vulnerable to injury because it is recessed and held more rigidly by the cuneiforms. This rigidity restricts motion and predisposes it to excessive bending forces. Hallux valgus (bunions) and a short great toe may also redistribute greater forces to the second metatarsal.

Metatarsal stress fractures are commonly the result of a change in running frequency, intensity and duration. A pes planus foot (flat foot) type or a change in running shoes, running surface or running mechanics may contribute to the development of a metatarsal stress fracture. A runner with a metatarsal stress fracture will present with forefoot pain of insidious onset that worsens as running continues. Eventually it will lead to pain with walking. On examination there is localized tenderness over the affected metatarsal and may have dorsal forefoot swelling. Axial loading of the metatarsal shaft as well as hopping in the affected foot will reproduce the pain. Resistance to active toe extension differentiates a stress fracture from tendinitis. X-rays within the first few weeks are often normal but later it may show a visible bony callus, periosteal elevation or a fracture line. History and a physical exam are usually sufficient for diagnosis but an MRI or bone scan can be performed for a definitive diagnosis.

Treatment includes rest from running and nonweight-bearing cross-training for 4-6 weeks or when pain free with daily activities for 2 weeks. A post-op shoe or pneumatic boot walker with full or partial weight-bearing may aid in healing. Runners should undergo biomechanical evaluation to determine if custom orthotics or a specific shoe type is needed to prevent re-injury. Return to running should be gradual.

The navicular bone

A navicular stress fracture is a high risk stress fracture that is more common among jumpers, hurdlers, sprinters and middle distance runners. Runners present with subtle and vague findings and are often go undiagnosed for months. The navicular bone is located in the midfoot and articulates with the talus, the cuneiforms and the cuboid bones. It is an essential part of the foot and is subjected to significant forces during running. During running, the central third of the navicular bone is subject to increased shear forces. These forces coupled with a poor blood supply make it the most common region of injury and poor healing resulting in a nonunion.

Runners will present with insidious onset of vague and intermittent dorsal midfoot pain that early on subsides with rest but progresses to pain with walking. On exam, localized pain is elicited at the apex of the navicular bone called the “N” spot. Plain X-rays usually are normal and a bone scan, MRI or CT scan are required for diagnosis. Treatment is 6-8 weeks of strict nonweight-bearing cast immobilization. A bone stimulator may facilitate healing and surgery is indicated for painful nonunion fractures. Return to running is gradual with the average length of time taking 5-6 months.

Tendons

Tendinopathies of the foot are typically caused by overuse and often abnormal running biomechanics contribute to the development of tendinitis. Most tendinopathies are self limited and respond to rest, ice, and topical or oral non-steroidal anti-inflammatory medicine. Tendinitis of the common extensor tendon of the forefoot is often secondary to acute alterations in mechanics. A recent increase in hill running is a common risk factor. Uphill running requires an increase in ankle dorsiflexion during the swing phase to achieve ground clearance. This action overworks the tibialis anterior muscle and tendon. Downhill running creates a longer and more eccentric loading of the extensor tendons from heel strike to the midstance phase of gait. Also, when running on unstable surfaces, runners tend to alter their gait by shortening their stride length to increase stability and thus the swing foot must increase dorsiflexion to maintain ground clearance. Tight shoe laces or improper fitting shoes may limit the normal glide of the tendon causing excessive friction and the development of tendinitis.

Examination of the dorsum of the foot reveals tenderness, swelling and crepitance. Passive stretching of the foot in plantarflexion, eversion, abduction and pronation elicits pain in the tibialis anterior. The condition is self limited and responds to rest, ice, and topical or oral non-steroidal anti-inflammatory medicine. Rarely immobilization with a walking boot or cast is needed. Lacing shoes that skip an eye reduces direct pressure over the extensor tendons that cross the prominent tarsometatarsal joint.

The flexor hallucis longus (FHL) tendon originates in the posterior lower leg along the fibula and courses posterior to the medial ankle intersecting with the flexor digitorum longus (FDL) in the midfoot. It inserts at the base of the first distal phalanx and functions as a strong great toe and ankle plantar flexor. Excessive repetitive hyper-plantar flexion with toe-off and increased forefoot pronation causes tendinitis. On exam, there is tenderness and swelling with palpation and resisted great toe plantar flexion causes pain. Treatment includes rest, ice and NSAIDS and often a biomechanical evaluation for orthotics that incorporate a forefoot medial wedge or a great toe extension.

The posterior tibialis tendon functions as a strong inverter of the foot and midfoot dynamic stabilizer. The tendon originates from the deep posterior medial leg and courses posterior to the medial malleolus and splits into two tendons. The first tendon inserts into the navicular tuberosity, the inferior medial cuneiform joint and the plantar surface of the medial cuneiform. The second tendon inserts to the inferior surfaces of the medial and lateral cuneiforms and the base of the adjacent metatarsals. During running, the posterior tibialis muscle supports the medial longitudinal arch of the foot and is eccentrically loaded as the foot transitions from a supinated heel strike to a pronated midstance position. Tendinitis in runners is caused by inadequate footwear, overpronating foot or certain changes in running form and regimen. In addition to treating posterior tibialis tendinitis with rest, ice and NSAIDS, orthotics or stability running shoes with medial arch support will aid in minimizing the stress on the tendon. Chronic cases can lead to tears and dysfunction of the tendon. Severe cases may require immobilization with a cast or walking boot.

The peroneal tendon is made up of the peroneus longus and peroneus brevis tendons. The tendons originate from the lateral compartment of the lower leg. The tendons course together posterior to the fibula then bifurcates at the distal ankle with the brevis inserting into the 5th metatarsal tuberosity and the longus continues medially and inserts into the base of the first metatarsal and the lateral aspect of the medial cuneiform. During running, the brevis acts to evert the hindfoot and the longus acts as a plantar flexion stabilizer of the great toe during weight-bearing. Repetitive overuse activity as well as lateral ankle instability, a cavovarus hindfoot alignment and ankle inversion injuries contribute to the cause of tendinitis. Examination may reveal a hindfoot malalignment and swelling, tenderness and crepitance of the tendon sheath. Diagnostic ultrasound may demonstrate swelling, tendon thickening, or tearing of the tendon. An accessory bone called an os perineum can be found at the base of the fifth metatarsal on x-rays. Again treatment includes rest, ice and NSAIDS. Physical therapy, a lateral heel wedge and a cortisone injection into the ossicle are alternative treatments.

Nerve conditions in the foot

Neuropathies of the foot are another common cause of foot pain in runners. These are typically the result of some form of nerve entrapment usually secondary to nonpenetrating trauma such as contusions, compression or stretch injuries. Repetitive lower limb movement and forces produced by the running motion may compress, stretch or dislocate nerves leading to symptoms of pain, numbness or tingling of the foot. Most of these entrapment neuropathies are transient but can result in permanent injury if left untreated.

The most common nerve entrapment syndrome seen in the foot of runners is an interdigital neuroma. It typically effects runners over 20 years and has a predilection for female runners. It is caused by repetitive trauma and biomechanical factors leading to compression of the nerve. The third digit web space is the most commonly effected. The nerve is compressed as it passes between the metatarsal heads plantar to the intermetatarsal ligament. Metatarsalgia or a metatarsal head stress fracture may lead to thickening and flattening of the metatarsal bone leading to nerve compression. Forceful toe dorsiflexion during push off compresses and stretches the nerve. Runners with a hallux valgus deformity, hypermobile first ray and hyperpronation as well as wearing shoes with a tight toe box are more prone to injure the nerve. Treatment includes modifying the running shoe with a wider toe box, a metatarsal pad and well padded. Decreasing toe dorsiflexion, correcting hyperpronation and separating the metatarsal heads also helps eliminate symptoms. In recalcitrant cases a cortisone injection or surgery is often needed to resolve the problem.

Tarsal tunnel syndrome is a nerve entrapment of the tibial nerve and its branches at the level of the ankle causing symptoms along the posteromedial ankle, medial foot or plantar foot. In runners, the nerve entrapment most often happens at the tarsal tunnel. The tarsal tunnel is a space formed by the medial calcaneus, posterior talus, medial malleolus and the flexor retinaculum on the medial side of the foot. Repetitive trauma with underlying biomechanical factors predisposes runners to developing tarsal tunnel syndrome. Hyperpronation, joint hypermobility, malalignment and stiff orthotics contribute to developing compression of the nerve. Symptoms increase with standing walking and running, especially on a banked surface which increases the degree of pronation. Tarsal tunnel syndrome is diagnosed clinically but sometimes electrodiagnostic studies may detect abnormalities in long standing cases. Conservative treatment includes rest, shoes and orthotics to control pronation including a medial wedge, and a change in running form or surface. A carefully placed cortisone injection under ultrasound guidance often gives excellent results. Surgery is indicated in severe cases after several months of debilitating symptoms unresponsive to conservative treatment.

Jogger’s foot refers to a syndrome of entrapment of the medial plantar nerve on the medial heel and longitudinal arch. The runner will report pain along the medial arch radiating to the plantar aspect of the first and second toes. Factors contributing to the entrapment of the nerve are high rigid orthotics, hyperpronation, previous ankle injury and a rigid first toe. Conservative treatment is often successful with modifying orthotics, addressing hyperpronation, arch strengthening and modifying running mechanics.

Plantar Fascitis

The topic of foot pain in runners would be incomplete without a discussion of plantar fasciitis. The plantar aponeurosis is a nonelastic fibrocartilaginous structure that originates from the calcaneal tuberosity and fans out inserting into each of the proximal phalanges. During running, the plantar fascia aids the foot by transforming from an accommodating landing pad on heel strike to a rigid lever for propulsion during toe-off. Toe flexion during heel lift-off pulls the plantar fascia taut passively by a windlass mechanism. This shortening mechanically locks the midfoot attempting to prevent the medial longitudinal arch from collapsing. This mechanism assists propulsive energy transfer from the gastroc-soleus muscle complex to the forefoot.

Runners with plantar fasciitis present with pain on the inferomedial aspect of the heel that intensifies with the initiation of weight-bearing. Symptoms often diminish at the onset of running but the pain returns after the completion of running. A clear etiology of plantar fasciitis does not exist but is thought to have a mechanical origin. Risk factors for the development of plantar fasciitis include pes planus (flat) foot, excessive pronation, decreased ankle dorsiflexion, increased daily weight-bearing and obesity. The diagnosis of plantar fasciitis is made clinically by history and physical exam. An x-ray is often performed to rule out other causes of heel pain. Finding of a plantar calcaneal spur on x-ray is nonspecific in that it is found in 50% of patients and 15-27% with it are asymptomatic.

Recently, diagnostic ultrasound has been found to be helpful in the diagnosis of plantar fasciitis. Increased thickness over 4.0 mm of the plantar fascia immediately distal to the calcaneal enesthesis and hypoechogenicity within the proximal fascia are diagnostic of plantar fasciitis.

The natural progression of plantar fasciitis is self-limited and resolves within one year in 80-90% of patients. No one treatment has demonstrated superiority to others despite numerous well controlled studies. Controlled trials of taping, chiropractic manipulation, therapeutic ultrasound and laser therapy have shown little if any benefit. Stretching and corrective orthotics have shown positive results in some studies. An intralesional cortisone injection produces short term benefit and increases the risk of spontaneous rupture of the fascia. An intralesional injection with platelet-rich plasma (PRP) is showing increasing evidence of efficacy. Surgery is considered only for patients with recalcitrant cases whom have exhausted all conservative therapy.

Biomechanics and foot injury

Variations in foot biomechanics during running also effect stress patterns on the foot. Foot strike among runners occurs in three different patterns: rear foot strike (heel lands first), midfoot strike (heel and ball of foot land simultaneously), and forefoot strike (ball of foot lands first then heel). During a rear foot strik,e the ground reactive forces at impact are increased and absorbed over a shorter period of time compared to midfoot strike and forefoot strike. Running shoes are designed with increased heel cushioning and a higher heel height to mitigate the increased forces. During midfoot strike and forefoot strike the ground reactive forces are absorbed through a toe-heel-toe gait. This pattern converts translational energy into rotational forces about the ankle which increases the load on the Achilles tendon and plantar flexors. The load experienced during midfoot strike and forefoot strike is half that of rearfoot strike and is absorbed over a longer period of time which decreases the effective magnitude of the forces.

A forefoot and midfoot strike running pattern requires a shorter stride length than rearfoot strike and therefore requires a higher cadence to maintain the same running speed. The increased number of foot strikes over a certain distance increases the energy costs of running resulting in increased stresses on musculoskeletal structures. Emphasis is placed upon muscle and tendon strength, endurance and stability rather than cushioning and motion control from the shoe. Thus, minimalist shoes are designed with a lower heel height, less cushion and less structure to accommodate the forefoot and midfoot strike pattern.

Recently, debate over barefoot running vs. shod running has emerged. Whereas shod runners are predominantly rearfoot strikers, barefoot runners are forefoot and midfoot strikers. Minimalist shoes are designed for the shod midfoot and forefoot strike pattern runner. It is unclear whether a runner is capable of changing gait styles without an increased risk of injuries. Changing from a rearfoot strike pattern, which relies upon shoes with cushioning and stability, to a midfoot or forefoot strike pattern requires strengthening the calf and plantar flexors as well developing dynamic stability. Although each running gait pattern has different injury types, to date, no studies examining the biomechanics of the two groups has demonstrated any difference in the incidence of injuries.

REFERENCES:

1. Kindred J, Trubey C, and Simons S. Foot Injuries in Runners. Curr Sports Med Report. 2011;10(5): 249-54.


2. Miller M. The Runner. Clinics in Sports Med. 2010;29(3).


3. Kaeding C. Stress Fractures. Clinics in Sports Med. 2006;25(1).

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date: November 28, 2015