Shin splints is a generic term that refers to a number of different conditions affecting the front inner or outer lower limb, but not the calf or Achilles.
The most common cause of “shin splints” is medial tibial stress syndrome (MTSS). This is caused by overload and irritation of the soleus muscle and posterior tibialis muscle on the inner edge of the shin. One predisposing risk factor for MTSS is poorly controlled pronation at the foot. This causes excessive rotation at the shin overloading these muscles creating either traction and irritation where the soleus comes off the tibia or overloading and aggravation of the posterior tibialis tendon. A tight calf muscle also contributes to this condition as it affects the ability of the foot to dorsiflex and contributes to excessive pronation.
You may be able to keep running whilst you suffer from MTSS, however a short lay off is recommended to let any inflammation settle down. The first course of action would be to get your gait and biomechanics assessed by a podiatrist to check whether your foot and ankle can control pronation. After that your physio should check your pelvic mechanics and glute muscle strength, flexibility and strength of the calf and intrinsic muscles in your feet. Treatment should consist of soft tissue release and acupuncture to the soleus and posterior tibialis as well as using supportive k-tape. Home exercises will focus on strengthening weak glutes, but also stretching tight calves and doing exercises to strengthen the muscles which support the arch of the foot.
The next most common injury in the shin area is stress fractures. There are two point affected by stress fracture – the back inner edge of the tibia or the front edge of the tibia. A stress fracture is an area of bone that has been overloaded to the point that the bone cells no longer adapt and a small area of bone swelling or even bone breakdown occurs. It can be difficult to diagnose initially and will sometimes require a CT scan or MRI to confirm the diagnosis – but you should suspect a stress fracture if you have quite distinct localised area of pain on the shins and a recent history of excessive training / increasing millage in your training plan.
We can usually get an indication of stress fracture from your story, training history and localisation of the pain. We can also use vibration on the tender area as a non-diagnostic sign to support the theory of stress fracture. We can use an ultrasound machine or a tuning fork over the area (both of these devices deliver vibration on to the bone) that may aggravate the symptoms.
The management of stress fractures is different to MTSS. You should immediately rest from running for a period of anywhere from 2-6 weeks to let the symptoms settle down. There may even need to be a period of immobilisation in an Aircast boot.
Low intensity pulsed ultrasound (LIPUS) is an effective treatment for stress fractures and poorly healing fractures. A daily dose of 20 minutes is required. Your physiotherapist should be able to apply this treatment for you or you can buy a home use LIPUS machine called Exogen (https://www.exogen.com/patient/). The pulsed ultrasound creates vibration that stimulates the bones cells to produce new collagen and heal the damaged area, however this process does take time.
After you have rested completely for a period of 2-4 weeks you can re-introduce non-impact exercise such as swimming and cycling and start some strengthening exercises for the calf and lower limbs. Your physio will also be able to guide you back into running with a graded return to running plan or you could start some unloaded running on an Alter-G treadmill.
The final most common condition that could be causing “shin splints” is anterior compartment pressure. The muscles of the lower leg are surrounded by fascia, that is in part non expandable. As you exercises and blood flow increases into the anterior compartment of the leg to the side of the shin, the pressure increases. In certain people this can restrict blood flow and nerve function in the lower leg and lead to pain. This pain is typically only present when you train and gets progressively worse, then resolved when you stop training.
The first line of treatment is to try and loosen the fascia with good deep tissue massage, dry needling and lots of home self-massage with a foam roller or tennis ball. If this fails to help you may well need to see a surgeon for a fasciotomy – a surgery where they make tiny cuts in the fascia to allow expansion of the muscles when you exercise.