Shin Splints Part II: An Anatomy Lesson

As I discussed in Part I of Shin Splints, the pain is from below the knee to above the ankle. It is a large area with many possible structures involved. In most cases the pain is self-limiting, but with some use of the 10 basic treatments (see Part I)  you are guaranteed that the rehab will be quicker than with just REST.



Let us review the anatomy of Shin Splints. The 4 basic types of shin splints are Medial (most common), Anterior (2nd), Lateral (3rd), and Posterior (4th). The medial group of muscles (function) are the posterior tibial (controls over pronation), flexor hallucis longus (stabilizes the big toe), and the flexor digitorum longus (stabilizes toes 2 to 5). Photo below shows where medial shin splints occur. Since over pronation, bunions (unstable big toes), and hammertoes (unstable lesser toes) are all common problems, this type of shin splint is the most common. More specific treatments of these problems include various methods in controlling pronation (there will be a series of posts on this topic), stablizing the big toe area or stablizing the lesser toes.These include toe separators/spreaders, shoe inserts with Morton’s extensions, and big toe spica taping to stabilize the big toe area, and toe crests, toe taping, reverse Morton’s extensions all to stabilize the lesser 4 toes.

Many patients purchase shoes too wide in the toe box leading to marked instability, especially when they have bunions. Too much room with resultant sliding around is just as bad on bunions and hammertoes as having too little room with resultant crowding.

The 2nd most common form of shin splints is anterior shin splints (see photo above). The muscles (functions) involved all help to control foot slap after heel strike, and then to help lift the foot off of the ground at toe off. Overuse situations can easily occur with hill running and increases in the speed of workouts. The muscle/tendons involved are the anterior tibial (controls over pronation and stabilizes the first metatarsal), extensor hallucis longus (stabilizes big toe and lifts toe up at toe off), extensor digitorum longus (stabilizes lesser toes and lifts these toes up at toe off), and the peroneus tertius (stabilizes the outside of the foot including the cuboid , 4th metatarsal and 5th metatarsal).



This muscle group is normally the weakest of the 4 groups and has to constantly pull against the more powerful Achilles tendon. As the calf/Achilles gets too tight/too strong with vigorous exercise, it is hard for the anterior group to keep up. These muscles will strain under the added stress of working against the tight Achilles. Hopefully, you can see, when someone has anterior tibial shin splints, treatment should be directed towards:
• Stretching of the calf

• Decreasing hills/speed for awhile

• Stabilizing pronation (medial support) or stabilizing supination (lateral/cuboid area support)

• Stabilizing any digit appearing unstable (with toe separators, taping, toe crests, etc.)

The 3rd most common form of shin splints is lateral shin splints (see photo). The muscle/tendons (functions) involved are the peroneus longus (stabilizes the lateral ankle against excessive supination and stabilizes the cuboid and the first metatarsal), and the peroneus brevis (stabilizes the lateral ankle against supination and stabilizes the cuboid and fifth metatarsal). So they stabilize the lateral ankle, and both sides of the midfoot area. Ankle braces, ankle proprioceptive exercises (see post on flat footed balancing), power lacing, and stable shoes if you pronate or supinate too much can all be part of the treatment.

The 4th common form of shin splints is posterior shin splints (see photo). The upper 2/3 of the calf is considered a shin splint if the pain is deep. This is normally a stress fracture on the posterior aspect of the tibia (very common in runners) and often misdiagnosed as calf muscle strain. It may also be a strain of the soleus muscle (deep part of the calf) where it originates on the tibia. The gastrocnemius (or gastroc) is the bigger, more superficial, muscle of the calf. The soleus muscle starts deep to the gastroc and becomes the other ½ of the Achilles tendon below. Therefore, the soleus functions to lift the heel. It also attempts to slow down pronation at heel contact, so over pronators may strain the muscle. It is harder to strengthen the soleus then the gastroc, so weaknesses may develop and muscle strains can occur with relatively minor overuse situations.



A further post will discuss various ways to strengthen the gastroc versus the soleus. In general, soleus strengthening is done with the knee bent 45 to 90 degrees and the ankle is then plantarflexed with resistance (pointed downward like a ballerina on her pointe shoes). Treatment of this type of shin splints must initially rule out tibial stress fracture which requires more modifications. Once tibial stress fractures are ruled out, functional changes include decreasing ankle plantarflexion (extension) and stabilizing pronation. Also, avoiding activities that produce a negative heel effect (see separate post), like getting off your seat in cycling. A slight biomechanical change in activities to minimize heel lift (ie. walking more flatfooted even when going up hills, or lowering the seat on your bike) can greatly speed up treatment.