The pain is at the anterior tibialis or along the tibia (shin / bone )? What do you mean by “freezes up?” Medial tibial stress syndrome, or shin splints typically occur on the inside of the lower leg either on the bone or at the junction of the muscle and bone. Does it hurt all of the time or just when activity occurs. If it hurts only with activity it would seem more like a chronic exertional compartment syndrome to me. Either way, it should probably be checked by a physician to rule out any stress fracture or look for biomechanical things that might be contributing. Orthotics might even be a potential fix.