Shin splints (medial tibial stress syndrome)

Shin splints, also known as Medial Tibial Stress Syndrome (MTSS), is a mechanical overload condition characterised by diffuse pain along the posteromedial border of the tibia. It occurs when the repeated stresses placed on the bone exceed its physiological capacity to adapt. This injury is particularly common in runners and is one of the main causes of lower leg pain in athletes.

Contrary to what its name suggests, shin splints is not simply an inflammation of the periosteum. Current scientific evidence shows that it is mainly a bone stress injury. When a runner increases training volume or intensity too quickly, bone remodelling becomes insufficient to repair the microstrain caused by repeated impacts: osteoclasts resorb bone faster than osteoblasts can rebuild it, leading first to bone microdamage and then to bone marrow oedema. The periosteum becomes painful secondarily, as a result of this bone distress and of the stresses exerted by the muscles that attach to the medial surface of the tibia.

Today, shin splints is considered to be part of the bone stress injury continuum, lying between the physiological adaptation of bone to training and tibial stress fracture. Without appropriate management, continued mechanical stress can lead to a true stress fracture. Early recognition of this condition is therefore essential to prevent this progression.

The tibia is the main weight-bearing bone of the lower leg and transmits loads between the knee and the foot during walking and running. With each stride, it withstands considerable forces generated by body weight, ground reaction forces and muscle contractions. The painful area in shin splints is most often located on the posteromedial surface of the tibia, in the middle or distal third of the bone, the area corresponding to the attachments of the soleus, tibialis posterior and flexor digitorum longus.

During running, these muscles exert repeated traction forces on the periosteum and help control ankle stability and support the arch of the foot. When stresses become excessive, the combination of bone compression forces and muscle traction promotes the onset of the pain characteristic of shin splints.

The soleus muscle originates from the posterior surface of the tibia and fibula before joining the Achilles tendon, enabling plantar flexion of the ankle and propulsion during running. The tibialis posterior muscle, for its part, arises from the posterior surface of the tibia, the fibula and the interosseous membrane before inserting mainly on the navicular and cuneiform bones: it is the main dynamic stabiliser of the medial arch of the foot and plays an essential role in controlling foot pronation. Finally, the flexor digitorum longus attaches to the posterior surface of the tibia and runs to the distal phalanges of the four lesser toes, contributing to propulsion and balance during the stance phase.

🔍 Click on the image to enlarge it

Biomechanics of the tibia during the running cycle

The tibia is subjected to considerable mechanical stress throughout the running cycle. In a runner, the forces transmitted to this bone can reach six to ten times body weight, depending on running speed, technique and surface. The bone acts as a true beam, able to absorb and then redistribute these stresses in order to limit their transmission to the joints.

At foot strike, a first stress peak occurs as ground reaction forces are transmitted to the skeleton; the lower leg muscles, notably the tibialis anterior and triceps surae, control this phase to limit the intensity of the impact. During the stance phase, the tibia bears almost all of the body weight and is simultaneously subjected to compression, bending and torsional stresses. During propulsion, the posterior lower leg muscles generate considerable force to move the body forward, which increases the traction stresses on the medial surface of the tibia.

In a healthy individual, these stresses stimulate bone remodelling and make the bone progressively stronger. When training volume or intensity increases faster than the bone tissue’s capacity to adapt, microdamage accumulates: the bone no longer has the time it needs to rebuild between sessions, which promotes the development of a bone stress injury.

Shin splints is one of the most common overuse injuries in runners. Depending on the study, it accounts for 13 to 20% of running-related injuries, and this proportion can reach nearly 35% in military personnel undergoing intensive training. It affects beginner runners and experienced athletes alike.

This condition is seen in many sports involving repeated impacts (trail running, athletics, football, rugby, basketball, dance, gymnastics), and more often during marathon preparation, intensive training camps or a return to sport after a break.

Groups at higher risk include beginner runners, military personnel, women, and athletes with low bone mineral density, relative energy deficiency in sport (RED-S) or a history of stress fracture.

Shin splints is a multifactorial condition: in the vast majority of cases, it does not result from a single factor but from a combination of several elements related to training, biomechanics, the runner’s morphology, their general health or their equipment. Identifying these factors is essential to prevent the injury and, above all, to avoid recurrence.

Training-related factors

The main risk factor is poor management of mechanical stress, resulting from an imbalance between volume, intensity and recovery. Increasing mileage too quickly, runs longer than usual, an abrupt return to sport or an accumulation of intense sessions do not give the bone enough time to adapt. Hills, long descents and interval training also increase the stresses placed on the tibia.

Insufficient rest between sessions, chronic fatigue or poor-quality sleep limit the capacity for bone remodelling.

Biomechanical factors

Weakness of the triceps surae, tibialis posterior, fibular muscles or gluteal muscles reduces the capacity to absorb stress. Limited ankle dorsiflexion and muscle stiffness alter the distribution of stress during running.

Impaired neuromuscular control, chronic ankle instability or poor pelvic stability promote increased internal rotation of the lower limb and increased foot pronation.

Stride characteristics

Prolonged overpronation increases the traction forces exerted by the tibialis posterior and the soleus. A low cadence combined with an excessively long stride (overstriding) increases ground contact time and the bending stresses on the tibia. Large vertical oscillation also increases impact energy.

Static morphology

A flat foot with overpronation increases the stresses on the medial surface of the tibia, while a high-arched foot (pes cavus), which is more rigid, absorbs impacts less effectively. Calcaneal valgus or varus, excessive internal rotation of the tibia or a leg length discrepancy can also contribute to bone overload.

Individual factors

Low bone mineral density, vitamin D or calcium deficiency, relative energy deficiency in sport (RED-S), smoking, insufficient sleep, chronic stress or a pro-inflammatory diet reduce the capacity for bone repair. Some metabolic diseases, such as diabetes, can also delay remodelling.

Equipment factors

The choice of shoes is an important factor, although it is generally not solely responsible for the injury. Worn-out shoes, an abrupt change of model, too rapid a transition to minimalist shoes, insufficient cushioning or recently modified orthotic insoles can change the stresses placed on the tibia. Very hard or steeply sloping surfaces also increase mechanical stress.

Shin splints most often presents as gradually increasing pain along the posteromedial border of the tibia, in the middle or lower third of the leg. Symptoms develop progressively over several days or weeks, in connection with a recent increase in training load.

At first, pain appears only after running. Over time, it comes on earlier during exercise and may then persist throughout the session; in advanced forms, discomfort is present when walking, or even at rest.

The pain is usually diffuse, extending over more than five centimetres along the posteromedial border of the tibia, which helps distinguish it from a stress fracture, where pain is usually very localised. Patients frequently describe a burning, pulling or deep aching sensation, sometimes with morning stiffness.

Clinical examination

The clinical examination is above all a process of elimination, used to confirm the diagnosis and rule out a stress fracture or chronic compartment syndrome. Inspection rarely reveals any visible abnormality; slight oedema on the medial surface of the tibia may sometimes be observed, but it is inconsistent. Palpation reveals diffuse, reproducible pain along the posteromedial border of the tibia, over a length of more than 5 cm.

The biomechanical assessment systematically looks for contributing factors (overpronation, flat or high-arched foot, limited dorsiflexion, weakness of the triceps surae, tibialis posterior or gluteal muscles), as well as pelvic stability and running gait.

Two clinical tests are commonly used: the Hop Test (hopping on one leg, which often reproduces the pain) and the Single Leg Heel Rise Test (which assesses the strength and endurance of the triceps surae and tibialis posterior). Assessment of ankle mobility, particularly dorsiflexion, and checking for pain provoked by tapping the tibia or by weight-bearing usefully complete the examination. Neurological and vascular examination is normal in shin splints.

Surgery has virtually no role in the treatment of shin splints. The very rare indications involve persistent pain despite several months of perfectly conducted conservative treatment, and after all differential diagnoses have been ruled out. As results are variable, it is considered only as a last resort.

Recovery time depends on how early the diagnosis is made, the extent of the bone injury and adherence to rehabilitation principles. Early forms generally resolve well within 4 to 8 weeks when loads are adjusted promptly. More advanced forms often require 8 to 12 weeks, or even longer if the return is delayed. If there is a true stress fracture, recovery can take several months.

Return to sport should never depend solely on the time elapsed, but on meeting satisfactory functional criteria.

Prevention relies above all on good management of training load: gradually increasing volume, intensity and frequency allows bone tissue to develop its capacity to adapt, while including sufficient recovery periods.

Regular strengthening of the triceps surae, foot muscles and glutes improves the capacity to absorb stress. Maintaining good ankle mobility, an appropriate running technique and a sufficient cadence also contribute to prevention.

Particular attention should be paid to sleep quality, nutrition and energy availability, as well as to screening for possible vitamin D deficiency or RED-S in at-risk athletes.

For a detailed approach, see our page “Preventing running injuries”.