Keys To Achieving Better Outcomes With Shin Splints
I love the academic challenge that shin splints pose to figure out what is wrong and what muscle or tendon is contributing to the issue at hand. I break down shin splints into medial, lateral, anterior and posterior shin splints.
Medial shin splints involve the posterior tibial tendon, flexor hallucis longus tendon or the flexor digitorum longus tendon.
Lateral shin splints involve the peroneus longus tendon or the peroneus brevis tendon.
Anterior shin splints involve the anterior tibial muscle, extensor hallucis longus tendon, extensor digitorum longus tendon or the peroneus tertius tendon.
Posterior shin splints involve the gastrocnemius muscle or the soleus muscle.
The actual definition of shin splints is pain between the ankle and the knee. There are a lot of structures with potential involvement that are important to consider when treating these symptoms.
When we treat shin splints, we can simply emphasize activity modification, some ice, general leg strengthening, and cross training, and most patients will do fine. However, if we treat shin splints with a little more zest, we can prevent reoccurrence. This may mean a longer running career for an athlete. For the patient who does not respond to simple measures, he or she could have compartment syndrome or tibial/fibular stress fractures. Muscle testing sometimes helps but most cases of shin splints are associated with muscle fatiguing when athletes get tired. This is hard to test in the office when the patient is rested although I normally have patients intensely work out or work out to the threshold of pain before their appointment late in the day. One muscle testing principle is to test the muscle in two basic positions: one where the patient has the advantage and one where the examiner has the advantage. When you test a muscle with the tendon shortened, you give the patient the advantage. When you test a muscle with the tendon stretched out, you (the examiner) have the advantage. At times, it is testing with the tendon stretched out that you find the weakness. You can pick up subtle weaknesses this way.
A thorough understanding of shin splints starts with classification as one of these four types and then delving into the function of the muscles. It is important to identify how the patient may have overused that muscle or muscle group. For the purposes of this blog, I will focus on medial shin splints.
If the patient presents with medial shin splints, we need to look for overuse with the posterior tibial, flexor digitorum longus and flexor hallucis longus muscles. These muscles have many functions but let us look at what they do at the ankle.
Since they all arise from the deep compartment, these muscles are ankle plantarflexors and ankle invertors. What is the primary ankle plantarflexor? That is the Achilles tendon but anything that makes the Achilles tendon weak can cause a patient to overuse one of the three muscles causing medial shin splints as they try to help the Achilles tendon perform its job. Typical weakness in the Achilles may stem from simple fatigue in doing a new sport or from adding hills to a running program. However, force-length physics considers an over-stretched Achilles or excessively tight Achilles weak. With the recent craze of zero-drop shoes, I now see more Achilles strain problems, the resultant weakness and then development of 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 three muscles to fatigue and strain as they attempt to decelerate the pronation. As the arch collapses in pronation, all three of these tendons can strain, but this is especially the case with posterior tibial tendon as the primary decelerator of rearfoot pronation at heel contact.
What are some of the causes of excessive pronation? Running itself with landing on the lateral side of the heel will cause two to four times more pronation than walking in many runners.1 Another one of the common causes of severe foot pronation is 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 influences 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 he or she has (medial, lateral, anterior, or posterior) and determine what the patient did wrong other than add a new sport. I need to check for excessive pronation. I watch him or her 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. I need the patient to wear his or her normal running shoes. If the patient is a pronator, I also want to categorize this as mild, moderate or severe so I can determine what level of support to offer in my treatment to lower the tissue stress threshold and allow healing.
This is where podiatry usually excels since proper shoes, custom or over-the-counter insoles, appropriate strengthening exercises and taping can speed up rehabilitation and prevent recurrence. In a future blog, I will discuss stress fractures, anterior and lateral shin splints, and other general rules.
Dr. Blake is in practice at the Center for Sports Medicine, which is affiliated with St. Francis Memorial Hospital in San Francisco. He is a past president of the American Academy of Podiatric Sports Medicine. Dr. Blake is the author of the recently published book, “The Inverted Orthotic Technique: A Process Of Foot Stabilization For Pronated Feet,” which is available at www.bookbaby.com.
- Williams 3rd DS, McClay Davis I, Baitch SP. Effect of inverted orthoses on lower extremity mechanics for runners. Med Sci Sports Exerc. 2003;35(12):260-268.