Shin splint anatomy and treatment

“Shin splints” – or medial tibial stress syndrome — has become a household word as more people pursue exercise for recreation and better health. The term describes a painful, potentially debilitating condition of the lower leg associated with overuse and characterized by strain of leg muscles at bony attachments resulting in pain ^1,2,3 which is aggravated by exercise and relieved by rest.⁴

Understanding the role of lower-extremity biomechanics, especially those involving the subtalar joint, is critical to effective treatment.

Not just athletes

Location of pain defines the condition as anterior or posterior shin splints.^1,3 It is an overuse injury most commonly found in long distance runners.⁸ However, individuals who engage in other recreational athletics, stand or walk on hard surfaces regularly for prolonged periods, or who are predisposed to arch collapse are also at risk for shin-splint formation. Occupations and activities that create excessive heel strike shock have also been implicated.

Untreated, shin splints can degenerate into more serious conditions, such as chronic compartment syndromes and stress fractures. However, the majority of patients respond well to conservative treatment.

The doctor’s three‑step goal should be to:

1. Relieve pain
2. Restore function
3. Prevent re-injury

A comprehensive plan of rest, manipulation, therapeutic exercise, and orthotic correction of biomechanical deficits enables many patients to resume full activities.

Anatomy of a shin splint

Biomechanical malfunction of structures in the lower leg and foot has been implicated in the development of shin splints. A brief anatomical review will enhance understanding of these causative factors.

The subtalar joint can be considered the functional center of the lower extremity. It comprises the articulation between the talus and calcaneus, and the calcaneus and navicular. ⁹ During gait, it performs two series of triphase motions: supination, including inversion, plantarflexion, and adduction; and pronation, with eversion, dorsiflexion, and abduction. ¹⁰

The primary muscles involved in subtalar joint motion are the anterior and posterior tibialis, gastrocnemius, and soleus (see Fig. 1).  Together, they move the foot in a pattern to elicit locomotion: ¹¹

• The anterior tibialis, running from the lateral tibia to the medial cuneiform and first metatarsal head, performs foot inversion and provides 80% of dorsiflexion power. It also is responsible for strong deceleration at heel strike. ²
• The gastrocnemius, attached to the lateral and medial sides of the distal femur, aids the soleus in plantar-flexing the foot.
• The soleus originates at the fibula and tibia and inserts with the gastrocnemius into the Achilles tendon, which is attached to the posterior calcaneus. ¹²
• The posterior tibialis, named for its point of origin, attaches to the navicular, cuneiforms, cuboid, and three middle metatarsals. It moves the foot into plantarflexion and inversion, and supports the medial foot and ankle.

When these lower extremity structures fail to adequately control subtalar joint motion, hypermobility is said to exist. Untreated, it can lead to development of shin splints. ¹⁰

Etiology

The literature varies greatly on specific causes of shin splints, though consensus prevails that subtalar hypermobility is the most common. Some sources have devised three etiological categories for shin pain: ¹⁰

1. Tibial stress fractures, with distinctive symptoms of pain and swelling at the tibia.
2. Ischemia of the deep posterior compartment, a vascular problem.
3. Soft tissue involvement (including myositis, fasciitis, periostitis, and more).

It is the latter category that will be considered in this paper, due to the effectiveness of conservative treatment with cases involving soft tissue structures.

Any discussion of shin splint etiology should logically begin with its most common cause, hypermobility. Pronation and gait disorders related to speed of pronation are responsible for this excess movement of pedal structures. ^{5,10,13,14,15}
Pronation is the compound motion of the foot and ankle during gait, a sequence of eversion, dorsiflexion, and abduction.¹⁰  It occurs in the contact portion of gait and is accompanied by inward leg rotation.¹⁶ The normal range of motion is between 25-30 degrees. ⁹ Variation in the degree and speed of pronation during gait is termed hypermobility. ^{5,10,13,14,15}

A pronated foot frequently exhibits a low arch and inward bowing of the ankles, often compensatory to heel‑foot or leg‑foot misalignment caused by other factors (see Fig. 2). ¹⁷ These factors may include:

• Tight triceps surae ¹⁸
• Forefoot varus deformity ¹⁷
• Valgus deformity of the heel ^10,17
• Tight posterior leg musculature unchecked by strong anterior tibialis ⁵
  A weak medial longitudinal arch ^5,15

Excessive pronation is said to increase both stretch and strain on the lower leg musculature. ¹⁰ This condition may be associated with soft tissue plastic deformation, characterized by loss of functional and structural integrity (see Fig. 3).  In addition, repeated maximal motion has been shown to be associated with muscle soreness. ^10,19,20

Muscles working overtime

Recalling the gait cycle of contact, midstance, propulsion, and swing, shin splint pain can be elicited throughout each phase. The anterior muscle group is normally active at heel contact, toeing off, and during swing. Hard walking surfaces and forefoot imbalance can force these muscles to work at midstance to aid deceleration or compensate for imbalance. This functioning out of phase subjects the muscles to increased stress, strain, and overuse. Pain in the anterior shin is elicited from heel strike to forefoot loading. ¹

Posterior shin splints are now sub-divided into medial tibial and soleus syndromes. ⁷ Medial tibial syndrome is commonly found in runners and dancers ^2,21, and is due to pain with use of the tibialis posterior muscle (often secondary to excessive pronation). ¹⁰ In normal gait, it is active during stance, from just after heel strike to just prior to heel lift. Prolonged or abnormal pronation causes excessive flattening of the longitudinal arch and that stretches the tibialis posterior muscle, sending pain up the posteromedial aspect of the leg. ¹

Excessive pronation is also cited as a causative factor in the soleus syndrome. Calcaneal eversion results in an angled pull on the Achilles tendon, which is continuous with the soleus. This stress can be transmitted to the soleus’ insertion along the tibia. ²²

Heel strike shock

The role of heel strike shock in shin splints should also be considered. Foot and ankle structures are subjected to considerable force during motion. Runners, for example, load the subtalar joint with a force of 3-5 times body weight with each ground contact.²³ It has been estimated that foot/ground contact occurs 5,000 times per hour of long‑distance running. ²⁴ Anticipation of heel strike shock can cause the toes to be raised higher as additional protection from impact. The foot is then lowered gradually to enhance shock absorption. This unnatural stress at plantarflexion can cause pain or injury to the anterior tibialis muscle. ²⁵

Heel strike shock force is transmitted and reduced by musculature and other shock‑absorbing parts of the body. Pronation contributes to soft tissue relaxation and rotation of leg bones that allow knee flexion, key defenses in protecting the upper body from shock stress. When pronation exceeds normal limits of degree and duration, the risk of injury increases. ²⁴ Soft-tissue stress can initiate or aggravate shin splints. Additionally, symptoms as far‑reaching as heel, hip, and back pain can result, as well as conditions such as Achilles tendinitis and plantar fascitis. ²⁶

Examination procedures

In examining a patient for shin splint conditions, the history will identify predisposing factors and characteristic symptoms. In most cases, the patient has begun a new activity that stresses the involved structures. ¹⁰ For example, runners may have undertaken dramatic mileage increases ^5,15 or started running on hills. ^2,5 The patient typically ignores the pain initially, dismissing it as muscle soreness, and continues to exercise.

Pain Characteristics — Shin splint pain manifests gradually and usually occurs during and after the activity. ¹⁸ In its mild stages, pain is reduced at rest, ^5,18 but worsens with increased weight‑bearing activity. Pain does not radiate, but can be described as deep seated, dull, and throbbing. ^5,15 The severity of pain depends on how long the patient has been affected. First cases may be mild, while those who continued to exercise may become debilitated from the pain.⁵

Examination — A shin splint diagnosis can be easy to confirm following examination protocols.  With the patient standing, look for signs of foot pronation. ^5,10 While in shoes, the foot will appear to fall over the inside edges. ¹⁴ Excessive lateral heel wear may also be noted. The barefoot stance may reveal valgus deformity in rearfoot alignment ¹⁰ and low arches (see Fig. 4). ^5,10 Anatomical leg length inequality must be ruled out during postural analysis. ⁵

Palpation — Extreme tenderness is elicited at the medial tibia, ^{2,5,8,15,18,27} the posteromedial tibia, ^2,18 and at the anterolateral tibia. ¹⁸ Palpable swelling of the area may be present. ¹⁸

Range of motion — A goniometer ²⁷ may be used to check for hypermobility. As an alternative, analyze gait ¹⁰ to detect a flattening of arches during stance and a quick, excessive flicking of the foot into eversion, dorsiflexion, and abduction while running.

Orthopedic tests — No specific tests are available; however, isometric contraction of the anterior or posterior tibialis may reproduce the chief complaint. ²⁸ To check, do a resisted muscle test for the anterior tibialis, posterior tibialis, and soleus muscles.

Neurological tests — Should be negative.

Radiological test — Plain film x‑rays of the leg should be taken to rule out stress fractures. ^10,18,27

Differential diagnoses

A few conditions of the lower leg mimic shin splints and should be ruled out during examination. It has been noted that several distinct diagnoses have evolved as knowledge increases on causes and characteristics of shin splints.

Stress fracture — Look for localized subperiosteal new bone formation, ¹⁸ local callus formation, or incomplete tibial fracture. ^15,18 It should be noted that a minimum 30% change in bone is required for an injury to be visible on plain x‑ray film. Finding a single, localized spot along the tibial crest that is sensitive to pressure distinguishes a stress fracture. ²⁵ Advanced imaging is often necessary to provide definitive diagnosis.

Trauma — Blunt force applied to the tibia causes the same pain characteristic of shin splints. Ascertain that the patient has not suffered trauma which produced no bruising.

Compartment syndrome — Unlike shin splints, this condition elicits pain with passive motion of the ankle. The patient experiences weak ankle flexion and altered sensation on the dorsum or sole of the foot. ²⁸ This condition should receive immediate surgical evaluation for decompression. ⁷

Treatment — Remembering the goals of pain relief, restoration of function, and reinjury prevention, a comprehensive plan of care should be followed. It is imperative that the patient cease all aggravating activity. ¹⁵ Elevating the legs at intervals throughout the day can be helpful.

Pain and inflammation can be reduced by a brisk ice massage. ^2,5,15,23 Apply cold until numbness sets in. ²⁹

Functional restoration

Functional restoration involves a four‑part program of manipulation, muscle stretching, muscle strengthening, and eccentric training:

1. Manipulation: Due to hypermobility, manipulation of the subtalar joint is contraindicated in initial stages. Areas that do benefit from chiropractic adjustment include the talocrural joint, other tarsals, metatarsals, and phalanges. This can relieve pain and correct other biomechanical abnormalities. ⁵ Evaluate the lumbar and pelvic regions, ⁵ as well as pubic and hip joints, to determine if the patient needs biomechanical alignment.
2. Muscle stretching: Stretching the calf muscles and tibialis posterior is critical to effective shin splint treatment. One method involves the patient leaning against a wall to elicit a gentle stretch in the gastrocnemius and Achilles tendon. The stretch is held for about 10 seconds, then both knees are bent to stretch the soleus and posterior tibialis for about 10 seconds. Recommend five repetitions twice daily. ¹⁵ To stretch the anterior leg musculature, patient sits on bent knees with foot plantarflexed directly beneath body weight. The foot is everted to produce maximal stretch and held for 10 seconds. Recommend one or two repetitions twice a day (see Fig. 5).

3. Muscle strengthening: Because shin splints arise from overuse, strengthening the involved muscles aids recovery as well as reinjury prevention. Subtalar joint stability depends on strong muscle support. Likewise, strengthening the anterior tibial muscle can improve balance with the more developed posterior muscle typical of athletes or dancers. The Thera‑Ciser^TM Therapeutic Exercise System from Foot Levelers, Inc., includes directions for performing dorsiflexion, inversion, and eversion to strengthen key muscles. The system has the advantage of being used in a seated position, thereby alleviating weight‑bearing stress that can increase shin splint pain.

4. Eccentric training: A regimen that includes an eccentric training component can help stabilize the ankle during impact. The patient stands on stairs as if to ascend, one hand on a railing for stability, and balls of feet at the stair edge. Slowly drop weight onto the heels to lower the body, then return to starting position. Three sets of 10 repetitions are recommended, increasing the speed of progressions over a one‑week period (see Fig. 6). ³⁰

Preventing re-injury

Once a patient has achieved relief from pain and developed greater muscle strength, normal activities may usually be resumed. To most effectively guard against reinjury, attention must be given to biomechanics of the pedal foundation and personal training schedules.

Orthotics — Lack of pedal instability (e.g., pronation and hypermobility) and heel strike shock have been noted as causal factors of shin splints. Orthotic therapy is crucial in helping eliminate biomechanical faults which affect the spine. Such therapy not only improves spinal support and alignment to enhance body structure and function, it also modifies minor deficits that inhibit the pedal foundation. Foot Levelers, Inc., offers custom-made, flexible orthotics which are designed to correct, control and support the feet. These orthotics are helpful in relieving the effects of heel strike shock, which can generate forces of up to 250% of body weight. Custom Stabilizing Orthotics provide critical support and shock absorption, yet are flexible enough to accommodate the kinetic interaction of foot structures during gait. Orthotic use should become a regular part of the patient’s lifestyle, even after discharge from supervised care. Resolution of shin splint pain does not eliminate the need for a balanced pedal foundation. If foot problems are allowed to return, bad posture habits may return, and shin splints may again develop. Discharge planning must address the importance of continued orthotic support.

Heel lifts — Leg length inequality is sometimes detected in cases of shin splints. Heel lifts are recommended to correct applicable deficiencies. ⁵

Shoes — Patients should be instructed to wear shoes that provide stability and shock absorbency. Good shoes have a strong heel cup, sturdy shank and an absorbent sole. ¹⁴ Even the best support shoe can be enhanced with orthotics. Foot Levelers orthotics are designed for a variety of footwear styles so that patients can benefit from therapeutic support at all times on their feet.

Returning to activity — The key to safe resumption of activity is a slow, gradual schedule. For example, runners should be limited to one mile or less initially, on a soft surface such as grass or sand. ^5,14,31 Progressive increases should be undertaken only if the patient remains pain‑free. Doctors can devise a similar approach to full activity for patients who are not runners.

In summary

Shin splint injuries can be adequately treated by the health care professional who has an understanding of lower extremity biomechanics. Conservative care can provide the patient with symptom relief and resumption of normal activity.

The major elements in an effective clinical management plan are:

• Comprehensive patient history, including training details
• Thorough examination and postural evaluation
• Cessation of aggravating activity during therapy
• Manipulation
• Therapeutic exercise
• Use of orthotics and lifts to correct biomechanical deficits
• Gradual and monitored resumption of activity

Patients need to realize that, while shin splints can be successfully treated, lifestyle changes may be required to prevent recurrence or degeneration to a more serious condition. Correction of faulty biomechanics, revised training schedules, and similar lifestyle adaptations may be required.

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Mark Charrette, DC, is a 1980 summa cum laude graduate of Palmer College of Chiropractic in Davenport, Iowa. He is a frequent guest speaker at twelve chiropractic colleges and has taught over fourteen hundred seminars worldwide on extremity adjusting, biomechanics, and spinal adjusting techniques. His lively seminars emphasize a practical, hands-on approach. He has authored a book on extremity adjusting and also produced an instructional video series. He has successful practices in California, Nevada, and Iowa and currently resides in Texas.

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