Shin splints are a common term for pain and inflammation on or around the tibia (shin bone). Usually associated with running and sports that require running, shin splints can be the first symptom of a stress fracture.
More typically, they present with an irritated thickening of the tibial periosteum (the outer fibrous layer that all bones have). The tibial periosteum is made of the same fibrous proteins as tendons and ligaments and are subject to the same strain, trauma, and maladaptive changes.
Shin pain can also result from strain in the lower leg musculature. The muscles around the tibia can feel tight and strained when subject to prolonged and repetitive stress.