Most shin splints, known as Medial Tibial Stress Syndrome (MTSS), can be attributed to overloading the muscles of the lower extremities or biomechanical irregularities. Muscle imbalance, including weakened core muscles lead to more lower-extremity injuries; also the inflexibility and tightness of the gastrocnemius, soleus, and Plantar muscles can contribute to shin splints. Increasing activity, intensity, and duration too quickly leads to shin splints because the tendons and muscles are unable to absorb the impact of the shock force as they become fatigued; also, the tibial bone-remodeling capabilities are overloaded. Some experts believe that this pain is caused from disruption of Sharpey’s fibbers that connect the medial soleus fascia through the periosteum of the tibia to insert into the bone. With repetitive stress, the impact forces eccentrically fatigue the soleus and create repeated tibial bending or bowing; thus, contributing to MTSS. The impact is made worse by running on uneven terrain, uphill, downhill, or hard surfaces. Improper footwear, including worn-out shoes can also contribute to shin splints.
While MTSS is the most common name, other conditions often overlap as causes including compartment syndrome and stress fractures. Females are 1.5 to 3.5 times more likely to progress to stress fractures from shin splints, but this is mostly due in part to females having a higher incidence of diminished bone density and osteoporosis. Shin splint pain is described as a recurring dull ache along the posteromedial aspect of the distal two-thirds of the tibia; the difference in stress fracture pain is that it is typically localized to the fracture site and is more proximal than the pain caused by MTSS. Studies have found that there are no neurological or vascular abnormalities associated with MTSS.
People with flat feet are especially prone to shin splints. Bio-mechanically, over-pronation is the common cause for medial tibial stress syndrome. It involves excessive inward rolling that causes tibial twisting and overstretching of the lower extremity muscles. Having poor form, such as leaning forward or backward too much, as well as landing on the balls of your feet and running with toes pointing outwards all contribute to the causation of shin splints.
Medial tibial stress syndrome is the most prevalent form of shin splints and can affect a broad range of individuals. It affects mostly runners and accounts for approximately 13% to 17% of all running-related injuries. High school age runners see MTSS injury rates of approximately 13%. Aerobic dancers have also been known to suffer from MTSS, with injury rates as high as 22%. Military personnel undergoing basic training see lower MTSS injury rates between 4% and 6.4%. Research has also shown that MTSS is more prevalent in women than men.
Risk factors for developing MTSS include:
- Excessive pronation at subtalar joint
- Excessively tight calf muscles (which can cause excessive pronation)
- Engaging the medial shin muscle in excessive amounts of eccentric muscle activity
- Undertaking high-impact exercises on hard, noncompliant surfaces (ex: running on asphalt or concrete
MTSS usually occurs late in a sports season for athletes or after prolonged activity for active individuals. However, onset can occur during the initial rigors of exercise after an individual has been inactive for a long period of time. A typical clinical presentation of this condition involves pain, palpable tenderness, and possibly swelling. Pain associated with MTSS is usually a recurring dull ache over the distal one-third posteromedial cortex of the tibia. In early diagnosis, individuals may experience pain at the beginning of a workout, which may go away by continued activity and then occur again at the end of the activity. As the syndrome progresses pain may stay throughout the whole training or during low intensity activity and may continue at rest. Range of motion in the ankle and foot should not cause pain.
Vascular and neurological examinations produce normal results in patients with MTSS. Radiographys and 3-phase bone scans are recommended to differentiate between MTSS and other causes of chronic leg pain.
Chronic lower leg pain results from various conditions such as medial tibial stress syndrome, stress fracture, chronic exertional compartment syndrome, nerve entrapment, and popliteal artery entrapment syndrome. These conditions often have many overlapping symptoms which makes a final diagnosis difficult. Therefore, an algorithmic approach was created to help in the evaluation of patients with complaints of lower leg pain, and assist in finding a diagnosis. Confirmation of the diagnosis is key and involves appropriate diagnostic studies including: radiographs, bone scans, magnetic resonance imaging, magnetic resonance angiography, compartmental pressure measurements, and arteriograms.
Treatment of shin splints includes rest, ice, and non-steroidal anti-inflammatory drugs (NSAIDS). Rest is the best way to treat shin splints as this gives the shins the full time necessary to heal. This can be a couple of weeks in mild cases up to about three months for severe cases. Acute therapy options for treatment include physical therapy modalities such as ultrasound, whirlpool baths, and electrical stimulation.
Correct diagnosis of the cause of pain or discomfort is necessary in order to choose the most appropriate treatment. Compartment syndrome may require immediate medical intervention, depending on the severity of the condition. Stress fractures require rest until the bone has healed. The inflammation of soft tissue known as shin splints can be initially treated with rest, ice to reduce inflammation, NSAIDS, and physiotherapy. For healing, rest may be required for a couple of weeks or up to 3 months for severe cases. Crutches may be necessary for temporary non-weight bearing, casting of the limb is only recommended for severe cases. Patients may be advised to decrease the duration or intensity of their exercise and then build it up slowly, as well as to exercise caution on high impact surfaces, until the muscles re-condition. Specially fitted footwear or an orthotic may be used to prevent a reoccurrence of shin splints.
Acute phase of treatment options include resting and applying ice. Therapy option includes physical therapy modalities such as ultrasound, whirlpool baths, phonophoresis, augmented soft tissue mobilization, electrical stimulation, and unweighted ambulation. Subacute phase is modifying the training routine, after the acute phase. The goal of the treatment should focus on modifying training regimens and addressing biomechanical abnormalities. Following the subacute phase is stretching and strengthening exercises. Exercises should focus on strengthening the tibialis anterior and other muscles controlling both inversion and eversion of the foot. Strengthening of the core hip muscles may also be beneficial.
Other ways to treat shin splints is to have appropriate footwear. Shoes with sufficient shock-absorbing soles and insoles can reduce forces through the lower extremity and can prevent repeat episodes of shin splints. Orthotics can also help with biomechanical problems of the foot. Over-the-counter orthosis help with excessive foot pronation, and mal-alignments may benefit from custom orthotics.
Potential treatments may include extracorporeal shock wave therapy, which is used to treat various tendinopathies of the lower extremity, injection methods, which has been used to treat injuries of the lower extremity, including cortisone. There are also surgical options. These are reserved for recalcitrant cases who do not respond with conservative treatment. “Posterior fasciotomy” is the procedure performed. This may include cauterization of the posteromedial ridge of the tibia, and results may not cause complete resolution but can improve the pain and function.