Part One of this series on shin pain looked at bony pain, in Part Two of this blog we look at Chronic Exertional Compartment Syndrome (CECS)
There are several muscle “compartments” in the lower leg, each includes muscles, blood vessels and nerves enclosed within soft tissue called fascia. During running the pressure gradually increases in the compartment until you start to experience pain. Symptoms often start at a predictable time during a run then gradually increase, reducing somewhat when you finish. It usually feels tight, tense and sore and can cover most of the shin area depending on what compartment is affected. If the pressure in the compartment is significantly raised it may affect the nerve, causing pins and needles, numbness or muscle weakness.
Symptoms will depend on what compartment is affected. The anterior compartment is most commonly affected, accounting for around 45% of cases, the deep posterior compartment is second most common at around 40%. Lateral compartment makes up 10% with the superficial posterior compartment around 5%.
The anterior compartment contains 4 muscles (Tibialis Anterior, Extensor Hallucis Longus, Extensor Digitorum Longus and Peroneus Tertius) the tibial artery and the deep peroneal nerve. Symptoms are usually felt within the belly of the Tibialis Anterior muscle. There may be weakness in dorsiflexion (lifting the foot) or toe extension. If the nerve is affected there can be pins and needles or numbness in the top of the foot and the first web space. In severe cases all power to dorsiflexion may be lost and a temporary or persistent “foot drop” can develop.
The lateral compartment contains 2 muscles (Peroneus Longus and Brevis) and the superficial peroneal nerve. Symptoms tend to be felt more along the outside of the shin in the muscles affected. If the nerve is affected there can be pins and needles or numbness in the front and outside of the shin and weakness in ankle eversion (turning the ankle out). I had this during my marathon training. I had a dull ache and pins and needles over the outside of the shin and eversion was weak. My symptoms were there for around 3 weeks then completely resolved with 3 treatments of acupuncture and a change of running shoes.
The deep posterior compartment contains 3 muscles (Flexor Hallucis Longus, Flexor Digitorum Longus and Tibialis Posterior) and the posterior tibial nerve. Symptoms are usually felt around the inside of the shin or back of the lower leg. If the nerves is affected there may be pins and needles or numbness in the sole of the foot and weakness of toe flexion and ankle inversion (turning the foot into).
The superficial posterior compartment contains 2 large muscles (Gastrocnemius and Soleus) and the sural nerve. If the nerve is affected there may be pins and needle or numbness on the top of the foot, on the outside and weakness in plantarflexion (pointing the foot down).
Diagnosis and Investigation
The gold standard for diagnosing compartment syndrome is intracomparmental pressure measurement. This is an invasive procedure and tends to be done after exercise to monitor pressure changes. MRI and Near Infrared Spectroscopy have also been used.
Something to consider with CECS is that if you are symptom free at rest then your doctor or Physio may find very little when examining you. There may be some signs, such as fascial hernias which are quite common in people with CECS but unless you exercise as part of the assessment they may find little else. This can lead to misdiagnosis and it is a condition that is commonly missed.
Causes of compartment syndrome
We know that muscles tend to swell during strenuous exercise and that the compartments in the leg are enclosed within fairly inflexible fascia. So why is it that some people develop a compartment syndrome and some don't?
I think much of it comes down to overloading one particular muscle group while we run. The muscle responds by strengthening and hypertrophy – an increase in muscle size – think Arnie! If the muscle is already enlarged before you start running, the added expansion during a run is too much for the limited space in the compartment. The result is that blood flow into the compartment becomes restricted, the tissues within the compartment become ischaemic (the reduction in blood supply leads to a shortage of oxygen and glucose which is essential for tissue to function). Tissue ischaemic causes pain. When you stop running the pressure in the compartment decreases and normal blood supply can return and symptoms settle.
So why is one muscle group being overloaded? And can you change it?
It's worth remembering at this stage that compartment syndrome comes in varying levels of severity. Also for many, their symptoms may well just be muscle tightness in response to being overloaded and not a fully developed case of compartment syndrome. Up until fairly recently it was thought that compartment syndrome responded poorly to non-surgical treatment and needed surgery but there is growing evidence that it can be treated without going under the knife. One study took 10 runners who were awaiting a fasciotomy surgery and changed their running style to forefoot running. All 10 avoided surgery and returned to running with reduced symptoms. Another smaller study by the same authors similar affects. Forefoot running isn't the only potential solution, a small study showed excellent results for anterior compartment syndrome just with change of footwear. Now, it's worth baring in mind that these are only very small studies and only on patients with anterior compartment syndrome. There are also a number of limitations with study design but at least they suggest that this condition can be changed non-operatively.
Address the causes
In part one of this blog we looked at how certain factors can place greater stress on parts of the bone leading to stress reaction and eventually, if continued, stress fracture. The principles here are similar. Like bony stress I do think it's also a “continuum”, that is it's a gradual increase in stress on tissues and not a sudden switch (like you either have compartment syndrome or don't). Earlier signs may be just tightening and discomfort in the muscle, something many runners experience and probably describe as “shin splints”.
Potential causes are;
- Training error
- Poor biomechanics
- Inappropriate or old footwear
- Poor running form
- Excessive running on solid surfaces
- Poor movement control
- Muscle weakness
- Reduced foot and ankle movement
- Tissue tightness
With compartment syndrome it may be pain free at rest, despite that it can be worth trying these measures to see if they reduce pain when you actually run.
- Ice – 10 to 15 minutes over the affected area
- Self massage
- Compression – many people find wearing compression socks very effective in reducing symptoms when they run
- Taping – tape can be used to help support the muscles to reduce overloading. It also tends to compress the area. RW have a nice technique here for anterior shin pain.
- Stretch the affected area
- Foam roller – be gentle and start in the pain free surrounding areas first
- Acupuncture – not something you can do on yourself obviously but I found it very effective.
Returning to running
One of the frustrating issues with compartment syndrome is that often symptoms return when running even after a prolonged period of rest. The challenge is to find a way to return to running without symptoms. With my lateral compartment syndrome I noticed some clear patterns. If I started a run too quickly I'd get symptoms, if I gradually built up speed it was far less. If I warmed up well symptoms improved. If symptoms developed when running I could usually reduce them immediately by switching from the road onto grass and slowing just a little. Speed work on concrete was the most aggravating and caused tightness and pins and needles in my leg. I ran Brighton Half Marathon when my symptoms were near their worst. The tightness kicked in around mile 3 and my ankle felt weak. I changed my position on the road regulary so I was running on slightly different cambers. By mile 5 I was symptom free again.
My point here is modify and overcome. See what you can change that allows you to run without your symptoms. It may be speed, distance, running surface, stride length, running shoes, pre-run warm up or training type (hills/ endurance/ interval work etc). In this way you can continue to run and by addressing the causes (as detailed above) your body will adapt to stop overloading one muscle group and then you can gradually return to full training. Bright Half Marathon was February 19th, I ran Brighton Marathon on April 15th completely symptom free.
Like all my posts on here this comes with a message; if in any doubt get checked out. It's always a good idea to have injuries assessed especially if they involve pins and needles, numbness or muscle weakness.