Shin Splints Discussion: PART I

                         Shin Splints 

 

     I love shin splints for the academic challenge to figure out

what is wrong and what muscle/tendon is involved. Since shin splints are so common at the start of cross country season, it is easy to get a little lazy with treatment since most get better. You have to take the approach that the athlete will not get better without your treatment, and that should inspire you. I breakdown shin splints into medial, lateral, anterior, and posterior. The muscles and tendons involved are summarized below for each. This discussion of shin splints will be broken down into 3 parts, today PART I.

Medial Shin Splints

Involves the posterior tibial tendon, flexor hallucis longus tendon, or the flexor digitorum longus tendon

Lateral Shin Splints

Involves the peroneus longus tendon or the peroneus brevis tendon

Anterior Shin Splints

Involves the anterior tibial muscle, extensor hallucis longus tendon, extensor digitorum longus tendon, or the peroneus tertius tendon

Posterior Shin Splints

Involves the gastrocnemius muscle or the soleus muscle

Common Location Anterior Shin Splints

Common Location Medial Shin Splints

Shin splints actually can be defined as pain between the ankle and the knee. There are a lot of structures that can be involved which are important when treating these symptoms. When we treat shin splints, we can simply use activity modification, some ice, general leg strengthening, cross training, and most patients will do fine. However, if will treat it will a little more zest, we can prevent it from reoccurring. This can mean an athletic will have a longer running career. For the patient who does not respond to simple measures, they could have compartment syndrome or tibial/fibular stress fractures. Muscle testing sometimes helps, but most cases of shin splints are related to the muscle fatiguing when tiring. This is hard to test in the office when the patient is rested, although I do normally have patients workout hard, or workout to the threshold of pain, before their appointment last in the day. One muscle testing principles is to test the muscle in two basic positions: patient has advantage and examiner has advantage. You can pick up subtle weaknesses this way. 

A thorough understanding of shin splints starts with you defining it as one of these 4 types and then delving into the function of the muscles and how the patient may have overused that muscle or muscle group. Today, this blog post, will focus on medial shin splints.

If the patient presents with medial shin splints, the muscles involved are posterior tibial, flexor digitorum longus, and flexor hallucis longus. We then have to look for overuse in one of its functions. So, what do these muscles do actually? These tendons have many functions, but let us look at what they do at the ankle. Since they all arise from the deep compartment, they are ankle plantar flexors and ankle invertors. What is the primary ankle plantar flexor? That is the achilles tendon, but anything that makes the achilles tendon weak can cause you to overuse one of the 3 muscles causing medial shin splints as they try to help the achilles perform its job. Typical weakness in the achilles is simply fatigue from the new sport they are engaging in, or just adding hills to their running program can fatigue the achilles. But, an over stretched achilles or excessive tight achilles, is considered weak by force length physics. With the recent craze of zero drop shoes, I have also seen more achilles and anterior or medial shin splints. 

The ankle inverter function is probably the more common cause of medial shin splints. What taxes the inversion strength of these muscles? Excessive pronation can cause these 3 muscles to fatigue and strain as they attempt to decelerate the pronation. As the arch collapses in pronation, the medial 3 are strained, but especially the posterior tibial and peroneus longus (a cause of lateral shin splints). 

So, what are some of the causes of excessive pronation? Running itself with landing on the lateral side of the heel will cause 2-4 times more pronation than walking in many runners. Another one of the common causes of severe foot pronation is achilles tightness called equinus. This tightness can be the cause of posterior shin splints, but also anterior and medial shin splints. This is why a complete understanding of achilles strength and flexibility is crucial. If the achilles is tight, it is harder for the anterior (extensors) to dorsiflex the foot (thus causing anterior shin splints). If the achilles is tight, the foot can pronate and the arch collapses (medial shin splints), both putting strain on the functions of the deep posterior compartment. If the achilles is tight, the forefoot is forcibly loaded by ground reactive force, making it difficult to bend the toes in propulsion. Stress is placed on the long flexors (medial shin splints) and long extensors (anterior shin splints).

So when a patient comes into my office with shin splints, I need to see what type they have (medial, lateral, anterior, or posterior) and if I can figure out what they did wrong other than add a new sport. I need to check if their pronation is excessive (and you have to watch them run since running and walking for a patient can be totally the same or different). I need to measure for achilles tightness or over flexibility since the achilles tendon can be the source of both power and problems for athletes. I need them in their normal running shoes. If they are a pronator, I also want to categorize them as mild, moderate, or severe, so I can determine what level of support needed in my treatment to lower the tissue stress threshold so they can heal. This is where podiatry usually excels since proper shoes, custom or OTC insoles, appropriate strengthening exercises, and taping can speed up the rehabilitation and prevent re-occurrences. PART II will discuss stress fractures, anterior and lateral shin splints, and other general rules.

The video below is on posterior tibial strengthening when a weak muscle is found in medial shin splints.

https://youtu.be/w3FXx4OFqec