Runners' shin splints explained

The lower leg is composed of two bones - the tibia and fibula - and four muscle compartments. The compartments are bound by a strong tissue called fascia.

Cross section through the lower right leg
(looking down towards foot)

Runners who develop shin pain which is brought on by exercise often complain of 'shin splints'.  This is actually not a very specific term and should be avoided if possible.

There are several different running conditions which can cause shin pain:

• Medial tibial stress syndrome (MTSS)
  
• Tibial stress fracture
  
• Chronic compartment syndrome (CCS)
  
• Calf sprain

For the physiotherapist or sports medicine specialist, differentiating between these is the key to the right treatment.

Medial tibial stress syndrome (MTSS)

What is it and what are the running symptoms?
This is very common in runners who will describe pain in the shin brought on by running, which may take hours or days to settle afterwards. There is tenderness over the inner border of the lower two thirds of the tibia which is due to a "stress reaction" of the lining of the bone on the inner border of the tibia, where the posterior tibialis muscle attaches. It is often associated with abnormal biomechanics, especially overpronation. It can also occur if there has been excessive running on hard surfaces and/or if trainers are worn out.

Treatment for runners
Treatment consists of a period of rest from running, maintaining cardiovascular fitness by cycling, swimming etc., and physiotherapy in the form of ultrasound, interferential, flexibility and strength work for the calf, achilles tendon and ankle.

Correction of any biomechanical abnormalities is important and your sports orthotist will work in conjunction with your physiotherapist for this. Finally, your training programme will need to be assessed to identify and change any training errors which may have contributed to the condition.

It is important that your doctor or physiotherapist excludes a stress fracture of the tibia. If they are at all suspicious of one, they may organise an x-ray (although a standard x-ray is often normal in the first month after stress fracture) or preferably a bone scan.

Tibial stress fracture

What are they and what are the running symptoms?
Stress fractures are "overuse" injuries of the bone to the point of mechanical failure.  A repetitive strain, secondary to the loading which occurs during running, causes bone trauma on a microscopic scale and, if not identified early, can progress to a stress fracture.

As with MTSS there is shin pain during a run which persists after the run. The pain occurs at an earlier stage with each successive run and often lasts longer afterwards.  There may be a "crescendo" of pain at night in bed after a run. There is a localised tender point over the fractured area of the tibia. A bone scan will show a localised area called a "hot spot" which is the stress fracture. Standard x-rays may initially appear to be normal but will later show an area called a "callus" (re-modelling of bone).

Treatment for runners
Treatment can depend on exactly which part of the tibia has the stress fracture. Typically however, a period of total rest from running (try using a flotation vest in the water instead) for six to eight weeks is required. This is followed by a graded return to running, initially alternating low mileage running with non-weight bearing activities, only gradually increasing the intensity if the leg remains pain-free.

Any biomechanical abnormalities should be addressed and, as with MTSS, the pre-injury training programme needs to be scrutinised. Some stress fractures take longer to heal - the length of time varying with the individual. Occasionally immobilisation in a plaster cast is necessary.

Stress fractures are more common in female runners and may be associated with overtraining, low body weight, amenorrhoea (lack of periods) and osteoporosis (bone thinning). If so, these should also be addressed by your doctor.

There is a large overlap between tibial stress fractures and MTSS, so do seek help from a chartered physiotherapist or a sports medicine specialist earlier rather than later for a professional diagnosis.

What is it and what are the running symptoms?
This occurs when the pressure within one of the muscle compartments of the lower leg increases during exercise, to the extent that the blood supply in the small vessels is reduced and the muscles (and sometimes nerves), in that compartment are compromised.

It can be caused by an increase in the size of the muscles which become too big for the inflexible surrounding fascia. It is most common in the anterior and the deep posterior compartments and may be associated with oversupination or overpronation respectively.

The superficial posterior compartment (containing the calf muscles gastrocnemius and soleus) is not affected as the surrounding fascia is loose.

Treatment for runners
The pain will occur during a run and is typically relieved by rest. It may feel like a cramp, a tightness or sometimes a burning. Often the sports medicine specialist can find no abnormality on examination as it only occurs during exercise. They will therefore need to do special pressure studies whilst you are running to obtain a diagnosis. Although rest may ease symptoms, they tend to recur on resuming training and the treatment of choice is opening the compartment surgically (fasciotomy).

N.B. Chronic compartment syndrome is different from acute compartment syndrome, which occurs after trauma and requires immediate attention. Acute compartment syndrome is not discussed here.

Symptoms and treatment
A tear of one of the superficial calf muscles (gastrocnemius or soleus) is best treated initially by RICE (rest, ice, compression, elevation). Early physiotherapy can be beneficial and treatment is along the lines of achilles tendon treatment. Remember that, as with most injuries, prevention is better than cure – thorough warming-up and cooling-down with stretching of the calf muscles, and the other leg muscles, is very important with all exercise, not just running.

Some of the other causes of lower leg pain in runners are:

• Referred pain from the lower back
  (This should always be checked by your physiotherapist or doctor as it is fairly common).
  
• Local nerve compression.
  
• Rarely, entrapment of the artery at the back of the knee.

Always remember that once a lower leg injury has been treated it is important to look at what caused it to avoid repetitions in your future running if possible.