Shin splints is a general medical term denoting medial tibial stress syndrome (MTSS), a slow healing and painful condition in the shins, usually caused by exercise such as running, jumping, dancing or other sports. Ten to fifteen percent of running injuries are shin splints.

The most common sources of shin splints are tendinitis, periostitis, stress fractures and compartment syndrome. The onset of shin splints is most common after exercise, caused by high impact training, excessive training, poor technique or biomechanical problems such as pes planus (flat feet) or pronation. Shin splints are also a common problem in military recruits during training. Some studies have suggested that shin splints are more common in women, but this may be caused by decreased physical fitness and smaller muscle size. Standing for long periods of time and wearing high-heeled shoes may also induce shin splints.

Stress fractures that result in shin splint pain come from overuse or repeated pounding of the feet. The downward pressure stresses the tibia which is the most prominent bone of the lower leg.

The pain associated with shin splints can also arise from the agitation of one or several muscles that surround the tibia of the lower leg. A study showed that the soleus, flexor digitorum longus, and deep crural fascia all originate in the region where patients complain of shin splint pain making them the most likely causes of pain. These muscles become irritated when the impact of steps causes the arch of your foot to collapse, stretching the muscles and tendons. This collapse of the arch is known as overpronation or "flat feet".

Shin splints are diagnosed using a number of techniques including taking patient history, physical examination, radiology and measuring the pressure within muscle compartments. Although the term "shin splints" is commonly used to describe any distal anterior lower leg pain, stress fractures and compartment syndrome are serious conditions which will require more significant medical treatment.

Magnetic resonance imaging has been used as a diagnostic technique; however, studies have shown mixed results. One study found that MRIs from patients with soft tissue injuries often appeared normal, limiting their effectiveness in diagnosing the condition, while MRI scans were described in another as "the single best technique in assessment of patients with suspected tibial stress injuries".  A study in 2006 indicated that high-resolution X-ray computed tomography (CT) scans had high accuracy in diagnosing MTSS.

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, while a stress fracture requires rest until the bone has healed. The inflamation of soft tissue known as shin splints can be initially treated with rest, ice, non-steroidal anti-inflammatory drugs and physiotherapy. Patients may be advised to decrease the duration or intensity of their exercise and then build it up slowly. Specially fitted footwear or an orthotic may be used to prevent a reoccurrance of shin splints.