Shin pain often gets described as the dreaded “Shin Splints”, the bane of many runners and an ongoing topic of discussion on the RW forums. The thing is shin splints isn’t really a diagnosis, it’s a collection of several potential diagnoses. Shin pain can be divided into 4 broad categories, bony, muscular, vascular and neural pain. As this is a complex area I’ve spread it across three blogs. In Part One we’ll look at bony pain and “shin splints”, Part Two compartment syndrome and Part Three tendonopathy and the rarer stuff – vascular and neural.
The surface of bone is covered in a layer called periosteum (see picture below, this link has details on ankle anatomy and terms like “medial” and “lateral”). This layer has a good blood and nerve supply – as a result it’s very capable of creating pain. Bone tends to respond to stress by strengthening, but, as you see from the diagram below, if the stress on the bone is too great then a “stress reaction” occurs. If this process continues without the bone having adequate rest to strengthen then a stress fracture can occur. There appear to be 3 stages to the development of a stress fracture;
- Bone marrow oedema
- Inflammation of the periosteum
- Stress fracture.
The early stages of this can be pain free. In fact some research has found stress fractures with no symptoms that then resolved spontaneously without intervention. During the second stage where the periosteum of the bone is inflamed, a diffuse (spread out) pain is often described. Sometimes runners find this is present at the start of a run but reduces as they continue. If this progresses to an actual stress fracture a more focal, more specific pain is expected. Usually this gets progressively worse when running, forcing a runner to stop.
The medial border of the tibia (on the inside) is a common area for stress fractures. They can also occur in the fibula and the anterior part of the tibia (the front of the shin) although this is more rare.
A medial tibial stress fracture is a non-critical stress fracture, this means it usually heals well as it has a good blood supply. It normally takes 4-8 weeks for symptoms to settle enough to start a gradual return to running but on average 8-12 weeks for full return to sport.
An anterior tibial stress fracture is a bit more complex and comes under a the “critical” banner. This means it takes longer to heal and has more complications. However people can often return to running after around 4-6 months depending on how well they heal.
Symptoms of a stress fracture include pain on palpating the bone (feeling along the length of the bone) and pain on any impact. You may also have swelling or bruising over the fracture site. The problem is it’s quite hard to diagnose a stress fracture without any scans/ X-rays. It’s a bit more straight forward to rule one out. If you can tolerate impact e.g. Repeated hops are pain free and palpating the bone is not tender, there is a good chance you don’t have a stress fracture. But if impact hurts and there is bony tenderness, that doesn’t mean you definitely have a stress fracture. The only way to tell would be through either an X-ray, MRI or bone scan. X-rays often miss stress fractures and so a second X-ray is done around 4 weeks later and you look for signs of bony healing. Even then it’s easy to miss. MRI or bone scan are better but harder to get on the NHS. This site has some excellent X-ray and scan results for several types of stress fractures, well worth a look. More info on stress fractures here from the American Orthopaedic Society for Sports Medicine.
Medial Tibial Stress Syndrome (MTSS) and Anterior Tibial Periostitis
Just to confuse you (and me) there are several other terms used to describe bony stress reaction. Some people see these as part of the stress reaction spectrum i.e. a stage on the path to stress fracture, and others see them as a separate condition.
MTSS is considered by some to be the medical term for Shin Splints. It refers to diffuse inflammation of the periosteum on the medial part of the tibia. Pain is expected to be diffuse and linear (along the bone) rather than focal (at one particular point). Some have theorised that MTSS occurs as a result of stress caused by the pull of deep fibres of the soleus muscle (in the calf) on the tibia.
Tibial Periostitis is another term for inflammation of the periosteum, when it occurs at the front of the tibia it can be termed Anterior Tibial Periostitis. One of the main muscles in the shin is Tibialis Anerior. It attaches to the front of the tibia. In theory the pull of this muscle on this area can cause the periosteum to become inflamed.
Management of Stress Fractures and Bony Stress Reaction
The first stage is to work out a likely diagnosis. If there is any question of a stress fracture then get it properly assessed! My old favourite if in doubt get it checked out!.
The assessment should then clarify the nature and location of the problem and aid you in managing it. This isn’t something that should be managed solely through advice from this or other sites. As you’ll see above a period of rest is often required to allow the bone to heal. This period is governed by the location and nature of the fracture you have. The help of a health professional is needed to decide how long this rest period should be and what other management is needed. It’s also likely you’ll need an X-ray, MRI or bone scan. The rest period is usually between 4 and 12 weeks but this can vary and will be longer for a “critical” stress fracture (such as the anterior tibia). Medial Tibial Stress Syndrome or Anterior Tibial Periostitis may require less rest but symptoms need to be closely monitored. The causes below are relevant to MTSS as well, as they all aim to address any factors that might place extra stress on the bones in the lower leg.
Use your rest period to help you identify the cause of the problem. This is where Physio can be very helpful. Most often it’s training error – excessive mileage, change in intensity or running surface, but other factors play a part;
Running shoes – Footwear that is too old will lose it’s ability to support your foot. Replace your shoes when you start to feel they have lost their spring or if the sole of the shoe loses it’s rigidity and becomes bendy. There is no definite figure in terms of mileage but a general guide seems to be to replace shoes every 300-500 miles. It depends a lot on you, your running and the shoe you have. Ensure you have the correct running shoe for your foot type, a running gait assessment may help this.
Altered biomechanics – over pronation, high arches and leg length difference have all been connected with stress fractures. Assessment from a podiatrist might help identify and treat these factors.
Poor running form – running form and biomechanics are intimately linked in running. Excessive hip adduction (the hip moving in towards the other leg during running) and over pronation during running have been linked with stress fractures in the research. Poor control of impact on landing could also lead to increased bony stress. Again, having your gait analysed could help identify this but bare in mind a 5 minute jog on a treadmill may not see how your gait changes when you’re fatigued after running a distance.
Poor movement control – again linked with biomechanics, running form and muscle strength, your control of movement will affect how your legs deal with impact. With good movement control the ground reaction force is dissipated throughout the leg (I.e. a number of muscles, tendons, ligaments, bones and joints deal with the impact of running). If movement control is poor this can place greater stress on certain areas. Check your single leg balance and single leg dip and compare left and right. Once you can tolerate impact you can also ask your Physio to assess your impact control – here they will look for excess movement in the ankle, knee, hip or trunk and help identify how to improve your control.
Muscle Tightness – tightness in the calf muscles or tibialis anterior can place increased stress on the tibia during running. Compare your flexibility on each leg. You can then add stretches to your rehab when guided to do so by your health professional. Stretching too early in the recovery process can be painful as it places stress on healing bone.
Ankle Joint range of movement – if your ankle is stiffer on one side this can have an affect on running gait and biomechanics. For example, ankle dorsiflexion (upward movement) is essential during impact, if the ankle is stiff in this movement it often compensates by over pronating. This can increase bone load in the tibia or fibula. One way to test ankle dorsiflexion is the knee to wall test, this is linked to calf muscle tightness as well as joint stiffness. Inward and outward movement of the ankle is also important (inversion and eversion), again compare left and right and work on it to correct the difference.
Muscle Weakness – strong muscles help to absorb the impact involved in running. Those muscles need not only strength, but also the endurance to keep working mile after mile. Look for any areas of muscle weakness in the leg. Compare both sides, check the calf (with repeated single leg calf raises) the quads (repeated single knee dips) the glutes (repeated clam, side lying leg lift, or single leg bridge) and the hamstrings (repeated hamstring curls in standing). You can also compare using weight machines for a more accurate measure.
General Health – in some cases (more commonly in women than men) a runner may have reduced bone density leaving them more at risk of stress fracture. This can occur through changes in diet, with conditions affecting the gut or bowel (e.g. Celiac disease, Crohn’s disease), with prolonged steroid useage and with menstrual irregularities.
Rehab following a stress fracture can be a frustrating and slow process. Once you’ve grown to love running it’s very hard to stop doing it! Despite this, it’s vital you listen to your GP/ Physio/ health professional during your rehab. They can guide you in returning to running and when to start strength or flexibility work. You can usually cross train when not running as long as no impact is involved and it remains pain free. Swimming and cycling are commonly recommended, but again be guided by your health professional. I have heard people on forums saying “I’ve been told not to run but….” it’s not worth the risk of running before a fracture is healed – you could face a much longer lay off if you do.