What are shin splints?
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.
Medial tibial stress syndrome
The most common cause of “shin splints” is medial tibial stress syndrome (MTSS). This is caused by overload and irritation of the soleus muscle, posterior tibialis muscle on the inner edge of the shin as well as the shin bone itself. One predisposing risk factor for MTSS is poorly controlled pronation at the foot. This causes excessive rotation at the shin overloading these muscles (and the bone) creating either traction and irritation where the soleus comes off the tibia, an overloading and aggravation of the posterior tibialis tendon as well as swelling in the bone (tibia) itself. It’s usually tender to palpate over a 2-4cm strip on the inner edge of the shin bone close to the ankle. A tight calf muscle also contributes to this condition as it affects the ability of the foot to dorsiflex and contributes to excessive pronation, as does weak glute muscles as this cause a hip drop when you land leading to more strain on the inner shin area. You may require an MRI to fully diagnose MTSS.
You may or may not be able to keep running whilst you suffer from MTSS, however a short lay off is recommended to let any inflammation in the bone and / or soft tissues 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. You may also need to change your running shoes to a motion control shoe and alter your running gait.
Posterior tibialsis tendinopathy / tensosynovitis
Another problem that can arise on the inner shin is posterior tibialsis tendinopathy. This is usually accompanied by inner shin pain as well as pain and swelling on the inner ankle. It is usually sore first thing in the morning and and warms up through the day. You can often still run with this injury as it warms up, but then is stiff and sore afterwards and the next day. We can see a thickened tendon surrounded by swelling on an ultrasound scan and treatment can include anti-inflammatoies, load management, strength exercises, shockwave or an ultrasound guided steroid injection.
Do I have a stress fracture?
The next most common injury in the shin area is stress fractures. There are two points 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. There is often pain at night with a stress fracture.
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, and sometimes we can see the stress fracture on ultrasound imaging.
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.
For stress fractures on the inner edge of the shin 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. A front edge of the shin bone stress fracture might be more problematic and will need additional management that your physio can discuss with you.
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. It may also be a good idea to see a nutritional therapist to make sure there are no underlying nutritional deficiencies that may have lead to this problem
Compartment syndrome
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. This should provide short term relief. However for longer term relief you will need to modify your training load (miles, tempo, frequency etc…) as well as consider training in lighter shoes. It would also be a good idea to change your running such as changing your stride length. Shortening your stride length and increasing your stride frequency might be a good starting point and working with your physio to address this is recommended. 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.
