Lower Leg Pain.
There are many causes of shin pain and calf pain, and making the diagnosis is often a complicated task. In my research work ( https://pubmed.ncbi.nlm.nih.gov/26884223/ ) to date I have focussed on debunking many of the myths around the diagnosis of chronic exertional compartment syndrome (CECS). CECS was though to result from elevated pressure in the muscle compartments of the legs , however the diagnosis is in doubt as the pressures reached do not stop blood circulating to the muscle, and so the pain seems to not come from pressure. The most common cause of shin or calf pain I see is related to strength capacity. You are asking the lower leg to do more work than it is conditioned to do from perhaps an increase in miles, a new shoe ( particularly the new carbon midsoles- which allow you to do more ankle work, change of training partners or clubs or you are coming back to running after a break.
We use our SSC Lab laboratories to test strength, power and the sequence of use in ankle, knee, hip and torso and start a focussed program you do yourself in the gym, on the road or track.
There are other causes, and the importance in making a diagnosis is vital, I broadly group these other diagnoses into power supply, blood supply, muscle or bone. The nerve supply from the back can be irritated by facet joint osteoarthritis, or a bulging lumbar disc, and a lumbar MRI scan can help us rule these out. More distally, the power supply as it passes around the proximal tibiofibular joint can cause irritation of the common peroneal nerve, more often this causes some weakness in dorsiflexion, but can be ruled out using nerve conduction studies. case for longer disk or modestly around that figure in the case of common perineal nerve.
With respect to the blood supply, either again this can be proximal at the femoral artery, or distally in popliteal artery entrapment syndrome. Here, duplex arteriogram and measurement of ABPIs can rule out the diagnosis. Muscle causes can include compartment syndrome where intra compartmental pressure measurement can be performed, and rarer metabolic causes where muscle biposy is needed. We cannot rule out bony causes such as periostitis or stress fracture must not be missed