Deep in pre-history, before the running revolution, any runner with pain between the toes and the hip had 'shin splints'. Now we understand that running injuries have identifiable and treatable causes, though these causes may not always be fully understood.
That said, it's more specific to refer to medial tibial stress syndrome (MTSS), compartment syndrome and stress fracture to differentiate the soft tissue and bony problems that may overlap. Many athletes use the term shin splints to refer to pain at the medial, inner area of the 'shin bone' or tibia. The front, or anterior portion of the leg may be involved, known as anterior shin splints. Now we recognize this as a possible stress fracture or a type of compartment syndrome.
Medial shin splints (MTSS) are painful several inches above the tip of the medial malleolus, or furthest point on the tibia. The medial muscles and tendons are frequently inflammed, though periostitis, an inflammation of the outer covering of the bone may occur. Micro tears at the origin of the muscle or in the muscle itself may be involved. A grade 1 injury involves vague discomfort following training. Eventually, pain comes on during exercise (grade 2), and if training is continued without treatment, the pain becomes so severe as to limit running altogether (grade 3). Those most commonly affected include runners during their first few months of training and more experienced runners who start training intensively for competition. Factors frequently
radually adapt to increased training loads. If not, the results are predictable.
Novice runners frequently train with shoes lacking proper cushioning or support/stability. For trained runners injury may follow changing from one pair of shoes to another, running in worn out shoes with excessive wear at the heels, or midsoles that have hardened. With excessive use the shoe may mold to your genetic faults with an inward collapse of the heel cup and a flattened midsole.
Biomechanically, foot type (flat or high-arched), leg-length discrepancy, an externally rotated hip and inadequate flexibility with tight calf muscles have all been implicated. However, excessive pronation is probably the primary factor as it places the medial structures of the leg under stress with an increased risk of injury. Tight calf muscles develop with hard training without adequate stretching. Hard training also develops a muscle imbalance as running increases the strength of the posterior calf muscles more than the anterior (front) leg muscles. This puts the anterior muscles at increased risk of injury at two points in the gait cycle. Immediately after the contact phase of gait, the anterior muscles function to slow down, or decelerate the plantarflexion, or downward motion of the foot. Tight posterior muscles force the anterior muscles to work excessively. At the toe off portion of the gait cycle, when the foot lifts off the ground, the anterior muscles dorsiflex, or lift up the foot so the toes will clear the ground as the leg moves forward. Tight calf muscles will cause excessive work of the anterior muscles at this point in the gait cycle, too. Downhill running also puts the anterior muscles at risk.
So, specific treatment includes finding out which specific factor is causing the injury. A change in running shoes may help. If the shoe shows signs of excessive wear or pronation, a new, firmer shoe may help control the muscular activity associated with over-pronation. If the shoe does not show excessive wear or pronation, then the shoe might be too hard or too soft. You might want to try a slightly softer pair, as the option is a pair of prescription orthotics to control the pronation.
For the novice, changes in the running gait might help. Running with a shuffling notion, as opposed to overstriding, will alter muscular function. The more experienced runner who has notched up his training with speed work should cut back on speed and frequency of training. Again, it's critical to allow the body to adapt to training stresses. Intervals should be done on a softer surface with shoes that are more shock absorbent than spikes. Cross training, including pool running are good alternatives to improving fitness until the pain subsides.
Gentle stretching, frequent ice massages, avoiding running on hard surfaces and downhill running are important. If pain persists, a visit to a sports-experienced doctor is recommended. An evaluation of your training/racing schedule and shoes is important. A bone scan might be necessary to rule out a stress fracture. Anti-inflammatory medication and physical therapy may also help.
A biomechanical examination is crucial. This will reveal the inbuilt faulty mechanics with which the runner has to cope with the amount of training his or her mind desires. Sometimes a prescription orthotic is the only way to compensate for these genetic limitations.
So, in summary: check your shoes and running surface, ice massage, stretch tight posterior muscles, allow your body to adapt to stress with gradual increases in training load and frequency, and if pain persists acquire a prescripton orthotic.