Osteopathic approach to achilles tendonitis & shin splints

Shin Splints & Achilles Tendonitis:

The muscle in the front is the tibalis anterior.

Shin splints results from tension within the tibial bone itself. There are 2 forms, one at the front of the bone and the other at the back of the bone. It is believed by many that shin splints developing from the front is the main form of shin splints (pic on the right). But in my opinion I have found it to be nearly always the back part of the leg, the tibialis posterior, which is responsible. I usually treat the patient as if they had both forms either way. By the time the bone starts to produce pain, the leg is already in a lot of tension anyway.

Triceps surae is the attachment of the gastronemius & soleus
muscles to the achilles tendon. The soleus is the muscle seen here.

Achilles tendonitis is simply ‘inflammation of the achilles tendon or triceps surae’ (pic below). For reasons to be discussed shortly the achilles tendon becomes under increasing stress and starts to develop micro tears. So when the muscle is engaged again and again in activities such as running, these micro tears become more and more irritated and inflamed. This is the pain felt at the bottom of the leg.

Here are the in depth reasons behind achilles tendonitis and shin splints:

The tibia bone:

The bone (pic above) is designed to transmit forces out of the body via the foot. The outer layer of the bone, the periosteum, is highly innervated and therefore very pain sensitive. When tension from the muscles pulls on the bone, the periosteum develops very minute tears on the surface and becomes irritated and inflamed. This inflammation combined with the increased pulling action of the muscles increases the actual pressure inside the bone. So every time you run or your foot impacts the ground, force shoot up the ankle joint into the tibia bone. Because the tibia bone is already highly pressurised this extra force only increases the stress in the bone further, hence the increase in pain. Repetitive actions like this, without treatment, can often lead to muscle tears, muscle ruptures or stress fractures. After a few years of dealing with this injury I have developed a technique to actually reduce the tension in the bone. Within my treatment I can also use my Bio-energy stimulation machine (B-E-St) to reduce the inflammation.

Toe off - the last action of walking:

The toe off phase is shown by the foot on the right.

Toe off is the expression given to the last action of your foot when it leaves the ground to eventually swing forward. For such a small action this is actually a very important process in walking/running. The function and mobility of the big toe must always be checked in any dysfunction or problem of the lower extremely, especially running injuries.

If the toe is restricted, it means you will be lifting the foot off the ground at a slightly earlier stage than normal. Consequently the tibialis anterior and calf muscles (triceps surae) have to engage earlier to lift the foot off the ground. Your centre of gravity will not reach the point where your body weight is directly over the standing leg. This means you will be leaning slightly backwards and off balance as your body weight passes behind the standing hip. The toe off phase is there to push the body forward enough so that it sits directly on top of the standing hip, knee and ankle. That means the forces generated by gravity will pass though all these joints evenly and out of the body as the other leg swings forward to complete your stride. Because the centre of gravity no longer sits directly over the standing leg, but rather just behind it, the trunk muscles (abdominals) and thoracic muscles have to contract to bring the upper torso forward to give you enough balance to stand on one leg.

So what is the actual consequence of engaging the tibialis anterior and triceps surae muscles at an earlier stage during your run? Normally when you have a smooth ‘toe off’ phase the actual motion of the body naturally enables the foot, knee and hip to work with less effort because the motion of the actual stride aides in the contraction of the various muscles. However by having to engage earlier, the muscles mentioned have to generate this motion themselves and of course this means the muscles generate a much greater contraction and energy output. Repeat this continually during a run over a period of time and the stress will gradually build. This principle is also equally applied to achilles tendonitis. The triceps surae are working harder and the achilles tendon gradually develops micro tears due to the high stress demand. Inflammation occurs and pain results.

The other aspect of having a restricted ‘toe’ off’ phase means your stride will also decrease. This is because the opposite leg has had to finish the swing phase earlier to compensate for the earlier lifting from the toe off phase. If it didn’t do this then both feet would be in the air at the same time and this is not possible when walking. Running is slightly different because both feet are usually off the ground, but the principle here still remains the same. The leg will compensate. Having a shorter stride obviously means the effectiveness of your performance is reduced.

Bunions, blisters, corns/calluses, halux valgus, hammer toe, arthritis, bruising, toe nail injuries (often when running the toe nail can peel off) and verrucas will all, in their own way, create some sort of big toe restriction.

Ankle restrictions via the mighty talus bone:

The talus is another part of the foot that must be checked in any running injuries. The talus is the one bone (pic to the right) that all forces from the body travel through to eventually disperse throughout the rest of the foot and then out into the ground. The tibia and fibula bone connect directly to the talus giving the ankle joint 2 predominant movements – plantar flexion and dorsiflexion (pic below). To simplify, this is the swinging motion of the foot. To achieve this effectively the talus rotates forwards and backwards within the tibia and fibula joint complex. However, it is possible for the talus to be shunted forward (anterior) or backwards (posterior) (pics below). If the talus gets stuck anteriorly then the movement of dorsiflexion (pic below) becomes somewhat reduced and if it is stuck posteriorly then plantar flexion becomes reduced. This consequently reduces the overall movement of the ankle joint in either direction and will result in very similar patterns as described above in toe off. The stride will reduce, the centre of gravity becomes displaced and the muscles work harder to lift the foot off the ground.

Dorsi flexion is when the toes point up.

The other aspect of talus restrictions is the distribution of force. The talus is designed to sit in the middle of the tibia/fibula complex. Therefore it is important that the force of gravity travelling from the body and down the leg travels directly through the talus. Whether the talus is restricted
anteriorly or posteriorly only means the force will disperse elsewhere in the foot, often in a non-physiological way.

An anterior restriction will result in the force travelling slightly behind the talus (green line in the pic on the right) and out through the calcaneus. (The red cross represents where the force will end). The natural motion of the talus is to slide forward on top of the calcaneus and into the connecting navicular and cuneiforms bones (purple and brown bones). With the medial arch linking all these bones together via the plantar fascia, the whole process acts like a suspension system. The navicular and cuneiforms act like a breaking system as everything compresses and bunches together. The medial arch behaves like a dampening spring to absorb nearly all the shock. However if the force passes behind the talus and straight into the calcaneus then this whole suspension system is missed and so the effect of this is to have a harder impact on the ground, which translates into greater force travelling back up into the tibia. Repeat this over time and it is no wonder the tibia bone becomes stressed. Remember also, when the foot hits the ground the achilles surae and tibialis posterior muscles are already in contraction to maintain plantar flexion as the heel hits the ground. Instantly on impact the tibialis anterior muscle contracts to decelerate the motion of the fore foot as it hits the ground. If the force or shock travelling up the bone is harder than normal, the contracted muscles will be put under greater tension because they have to work harder. 

Consequently if the talus is restricted posteriorly (pic just below) then the force of gravity passes in front of the talus and straight down into the medial arch mechanism, missing the forward motion of the talus on the calcaneus and the resulting bunching together of the navicular and cuneiforms. In time this stresses the medial arch, resulting in many possible foot injuries, such as plantar fasciitis. However the tibialis posterior and tibialis anterior muscles both have strong attachments into the under-surface of the foot, into the medial arch itself. Stress the medial arch and these muscles become naturally elongated and start to behave like contracted muscles. In time they will become weaker as they acclimatise to the elongation stress. When these two muscles become stressed they tighten and create an overall increased pull on the tibia bone – shin splints. This then leads us nicely onto what is commonly talked about – overpronation. 

What is over-pronation and supination?

Pronation is actually a name of a specific type of movement with supination being its opposite movement. When the foot over pronates you get a collapsing of the medial arch leading to flat foot, which is also known medically as pes planus. The medial arch consisting of the plantar fascia, which acts like a bow string, connects the cuneiform, navicular and talus bones together, creating an arch. When the foot strikes the ground the gravity force of the body travels down the tibia bone through the talus into the navicular, cuneiforms and out into the toes. As the foot strikes the ground the talus actually moves forward on top of the calcaneus and pushes into the navicular. In turn the navicular pushes into the 3 cuneiform bones and together everything works like a breaking mechanism. At the same time the arch that these bones form flattens and the spring like structure of the plantar fascia stretches under the increased pressure. This acts like a spring or suspension system.

Medial arch. Looking at the foot from the inside.

So if you have flat feet or collapsed arches then you can understand that both these mechanisms don’t function efficiently and therefore the force has to be absorbed elsewhere in the foot. This is over pronation.

There are 3 places this force tends to go. The heel (calcaneus), the big toe (metatarsophalangeal joint MTP1) or the transverse arch.

The calcaneus bone has no shock absorption except the fat pad underneath it. Repeated stress in this area will likely lead to plantar fasciitis or heal spur type injuries.

During the normal walking cycle the heel hits the floor first, following to the outside of the foot where it reaches the little toe (this is called the lateral roll). From here the natural motion and weight travels across the transverse arch to the big toe (this is called the medial roll) and then lastly to toe off. When the medial arch has collapsed the lateral role of the foot during this walking cycle will be either partially or completely missed. So instead of having a lateral role movement the force just travels straight across the foot to the MTP1 joint, hitting it more directly and more forcefully. This will lead to chronic stiffness of the big toe and reduced ‘toe off’ function, discussed above. Additionally when the arch has collapsed you can develop an unnatural inward rotation or twisting of the MTP1 joint, albeit it a mild one and this leads to the inner part of the joint taking the biggest brunt of the force. Repeated stress and offloading of force here can lead to painful calluses, bunions and halux valgus type injuries.

Longitudinal arch = medial arch.

The transverse arch is the arch between the metatarsalphalangeal joints, travelling from the little toe to the big toe (pic to the right). It is smaller than the medial arch. The purpose of the transverse arch is much the same as the medial arch, to dampen the gravitational force as it passes from the lateral roll movement to the medial roll movement of the foot. Stresses to this arch can lead to plantar fasciitis as this is the other insertion area for the plantar fascia.

Future installment:
I am currently in the process of writing about knee mechanics and their impact on these injuries. I will also look at the fascial chains running through the leg and how the viscera play their role. I hope to get this released soon. Thanks.