Shin splints

The term ‘shin splints’ is often used as a blanket description of any persistent pain occurring between the knee and ankle in an athlete. The condition has a number of names including Exercise Induced Leg Pain (EILP), Chronic Exertional Compartment Syndrome (CECS),  Exertional Lower Limb Pain (ELLP), and Biomechanical Overload Syndrome (BOS).  The term CECS with be used in this text.

The condition presents as a gradually increasing cramping or aching pain (fullness) along the side of the shin, and can be due to stress on several structures including bone, nerve, muscle, and fascia.

Originally called ‘fresher’s leg’, a more accurate description of this type of exercise induced leg pain comes with the various ‘compartment syndromes’ which identify the anatomical structures affected. The lower leg contains four compartments.  The anterior compartment contains the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and the anterior tibial artery and vein. The lateral compartment contains the peronei and the superficial peroneal nerve. The superficial posterior compartment contains the gastrocnemius and soleus and the deep posterior compartment contains the tibialis posterior, flexor digitorum longus, flexor hallucis longus, the peroneal artery and vein, and the posterior tibial artery and vein.  The tibialis posterior is sometimes considered to be within its own separate (fifth) compartment.  The structures overlie and take attachment from the tibia, while the deep and superficial posterior compartments are separated by the deep transverse fascia of the leg.

Direct bone pain may occur with a stress fracture or stress reaction, and indirect bone pain can come from traction through muscle fascia causing inflammation of the periosteum.  Periosteal inflammation (periosteal contusion) may also be instigated by direct trauma such as a kick to the shin. Muscular pain may be acute immediately following exertion, or chronic building over time. Chronic pain may eventually become noticeable even at rest. Neural compression may be local or pain referred from nerve root compression in the lumbar sacral spine. Finally, vascular signs may exist in cases of popliteal artery entrapment.

The pathophysiology of the condition is generally thought to include a sudden increase in muscle bulk in parallel with reduced compartment compliance due to stiffening and thickening of the connective tissue forming the compartments.  Although muscle hypertrophy  is a key feature of CECS, it is not the only cause.  Bodybuilders rarely suffer from the condition, so the rate rather than the amount of muscle hypertrophy may be important.  Vascular congestion results from reduced microcirculation and vascular congestion through a reduction in venous return.  Intercompartment volume increases faster than the ability of the compartment wall to adapt.  The resultant changes in oxygen balance to nerve and muscle, direct sensory nerve stimulation of fascia or periosteum and  kinin release have all been proposed as sources of pain (Rajasekaran et al 2012).

 

Anterior compartment syndrome

Anterior compartment syndrome involves pain in the anterior lower leg, which is increased in resisted dorsiflexion. There is usually a history of a sudden increase in training intensity, frequently involving jumping or running on a hard surface. The anterior compartment muscles swell, and in some cases hypertrophy occurs, giving a tense drum like feel to palpation. The fascia covering the muscles may be too tight and inflexible to accommodate the increase in size. As a consequence, when the muscles relax, their intramuscular pressure remains high and fresh blood is unable to perfuse the tissues freely. This decrease in blood flow leads to ischaemia with associated pain and impairment of muscle function – resisted dorsiflexion often scoring lower than the unaffected limb.

Usually, when a muscle contracts, its blood flow is temporarily stopped. Arterial inflow occurs once more between the muscle contractions as the intramuscular pressure falls. Normal resting pressure within the tibialis anterior in the supine subject is about 5–10 mmHg, increasing to as much as 150–250 mmHg with muscle contraction. Muscle relaxation pressure, that which occurs between repeated contractions, is between 15 and 25 mmHg in the normal subject, but in athletes with anterior compartment syndrome pressures may rise to 30–35 mmHg and take up to 15 minutes to return to normal values (Styf, 1989).

The intracompartment pressure (ICP) may be measured using several invasive techniques including mamometry (side-ported, split catheter, or standard needle) and solid state transducer intracompartment catheters (Hislop and Tierney 2011).  Non-invasive techniques are also available using a small (5 mm diameter) indenter to measure quantitative hardness of the shin compartment as an objective measure of tissue tension (Steinberg, 2005).

 

Lateral compartment and superficial peroneal nerve

This is a less common cause of shin pain and occurs when the peroneal muscles are affected, often by hyperpronation. The condition may have existed for some time but is brought to the fore when running begins. Again, there is ischaemia and pain, but in addition the superficial peroneal nerve may be compressed as it emerges from the lateral compartment.

The superficial peroneal nerve lies deep to the peroneus longus and then passes forwards and downwards between the peronei and the extensor digitorum longus. It pierces the fascia in the distal third of the leg where it divides into medial and lateral branches to enter the foot. Entrapment may occur if muscle herniation or fascial defects exist. In addition, ankle sprain, fasciotomy and an anomalous course of the nerve have been suggested as contributory factors (Styf, 1989). Clinically, the patient presents with loss of sensation over the dorsum of the foot, especially the second to fourth toes. Certain resting positions may compress the nerve and bring on the symptoms. To test the nerve, it is compressed over the anterior intermuscular septum 8–15 cm proximal to the lateral malleolus while the patient actively dorsiflexes and everts the foot. Tinel’s sign, involving local percussion over the compression site, may be positive.

 

Posterior compartment

The superficial posterior compartment contains the soleus and gastrocnemius (together with plantaris). These muscles are usually affected by trauma rather than ischaemia.  Pain occurs within the calf bulk and is increased with resisted plantarflexion.

The deep posterior compartment contains tibialis posterior, flexor digitorum longus (FDL) and flexor hallucis longus (FHL), and is a common site for CECS in distance runners.  Pain in this region is usually experienced over the distal third of the medial tibia either within muscle or directly over bone.  The latter described as medial tibial stress syndrome (MTSS).  The exact site of pain will vary depending on the specific structures affected,  with bone shaft being deeper than periosteum or muscle.

 

Medial tibial stress syndrome

Medial tibial stress syndrome(MTSS) is shin pain over the distal third of the inner aspect of the tibia. The disorder is a traction periostitis, and pain in this region must be differentiated from CECS of the deep posterior compartment (above).

Type I MTSS involves microfractures or stress fracture of the bone itself. The patient is usually a runner who has recently increased his or her mileage. The stress imposed by the sport exceeds the ability of the bone to adapt and remodel. The condition may present as a stress fracture showing a concentrated positive uptake in a single area on bone scan and point tenderness to palpation, or as a diffuse area along the medial edge of the tibia giving more generalized pain. In chronic conditions which have existed for some time, the tibial edge may be uneven due to new bone formation.

Type II medial tibial stress syndrome involves the junction of the periosteum and fascia, and occurs particularly in sprinters and those involved in jumping activities. Pain is maximal just posterior to the bone, and has often persisted for a number of years. Initially, pain occurs only with activity, but as the condition progresses discomfort is felt with walking and even at rest. In this condition compartment pressures may not be elevated, and the periosteum is unchanged.  During the chronic stage of this condition, adipose tissue has been found, during surgery, between the periosteum and underlying bone (Detmer, 1986). In the early stages of the condition the periosteum may heal back with rest, but when the condition becomes chronic, it is unable to heal, and continues to cause pain when stressed by activity.

The type III condition involves ischaemia of the distal deep posterior compartment and presents as a dull aching over the posterior soft tissues brought on by exercise. Intramuscular pressures are elevated  and remain elevated after exercise.

Traction from muscle attachment is the most likely cause of the condition, the attachment of tibialis posterior normally being associated with the condition. However, both the soleus and flexor digitorum longus may also be implicated. The medial fibres of soleus and the attached fascia extend over the deep posterior compartment forming a region known as the soleus bridge, an area implicated in MTSS. Excessive pronation is thought to be a significant factor in the development of the condition. The muscles attaching to the posterior border of the tibia become overactive in an attempt to slow the rate of pronation and limit its degree. This deceleration results in eccentric overload and the consequent traction stress, which may be higher in those who overpronate (Bradshaw et al 2007).

The condition usually demonstrates a clear x-ray, but bone scan can show patchy diffuse areas (bone stress reaction) rather than the focal uptake of stress fracture, although asymptomatic individuals can also demonstrate these appearances (Batt et al 1998) show diagnosis must be multifactorial.

 

Management of shin splints

Initial management of shin pain includes a reduction of the stresses which caused the condition in the first place. This involves accurately identifying the structures affected and taking a thorough history of causal factors, particularly stresses imposed during training. Temporary pain relief may be achieved using deload taping to limit the fascial traction thought to be part of the pathology. Taping is applied in a spiral beginning on the lateral aspect of the ankle just above the lateral malleolus. The tape is wound around the shin going behind the calf and emerging once more onto the front of the tibia. As the tape is applied it is pulled proximally to unload the fascia. Another approach is to place anchors just below the knee and just above the ankle, and connect the anchors with 2 or 3 strips of zinc oxide taping gathering the skin up to take tension away. Both tapes alter the fascial loading and give temporary relief only.

 

 

 

 

 

K tape (kinesiology tape) has been shown to decrease the rate of medial loading in athletes with MTSS (Griebert et al 2016).  A single Y-strip is applied with the base of the Y at the superomedial aspect of the tibia.  The Y tails pass down the medial tibial anterior and posterior to the medial malleolus to the arch of the foot.  A higher time to peak force (TTPF) was seen in healthy volunteers and those with MTSS following K tape application, demonstrating a slower rate of medial loading.

Biomechanical assessment of the lower limb is often helpful and prescription of orthotics should be made where necessary.  An increased navicular drop (reduction of the medial arch height on weightbrearing) has been linked with the development of MTSS (Hamstra-Wright 2015).  Correction of overpronation and reduced medial arch height would therefore seem appropriate, at least in the short term to reduce symptoms.

Initially, rest and anti-inflammatory modalities may be used to allow the acute inflammation to settle, but external compression and elevation of the limb can exacerbate the problem in some athletes so symptom reaction should be monitored.   Some athletes report anecdotal improvement using compression socks however.  If training stresses can be modified, and the condition has been identified early enough, this may be all that is required.

One of the key points about bone pain in shin splints is that the bone is reacting to stress (see also this blog on overtraining syndrome).  All tissues react to a stressor, be it impact, weight training, or stretching.  The demand placed on the tissue challenges it and stimulates adaptation.  If the tissue stress is not great enough, no adaptation will occur (think of lifting very light weights in the gym).  If the stress is optimal, tissue adaptation will occur, but if the stress is excessive, the breakdown of tissue will be greater than its ability to adapt – now we have overtraining, and if the stress continues possible injury.

The initial management of shin pain is to reduce loading on the tissues.  This may mean complete rest if the condition is very painful, or just reducing running mileage if there is less pain.  Unloading the tissue with taping or changing footwear or running surface may also help.  Once pain begins to subside, tissue loading should resume, but be graded.  Simply to rest until pain has eased and then return to running at the same level will challenge the now weakened tissue too much.  Begin at a level which does not cause an excessive reaction.  If the next day there is no bone pain, gradually built up the tissue loading (mileage, changing surface, speed work, hill work) while monitoring the body reaction.  With time athletes will be able to do more before pain onset.  Eventually the damaged tissues will have been strengthened sufficiently to return to full pain free training.

In chronic conditions in which conservative management has failed, decompression by fasciotomy or fasciectomy may be called for. With fasciotomy the fascia of the affected compartment is surgically split along its length. The procedure is often performed on an out-patient basis, with two incisions being made, at the junction of the proximal and middle third of the leg and the middle and distal third. Athletes mobilize early and are often able to resume running after 3 weeks. Where fasciotomy fails, fasciectomy may be performed. Here, a longer open incision is made and a ribbon of fascia is removed. Because a longer incision is made, there is an increased risk of infection and dehiscence (incision bursting open). A longer rehabilitation period may be required, depending on incision healing time. Full return to sport may be expected in 8−12 weeks.

 

Running re-education

Running form can be used effectively as part of the management of this condition.  Several common errors may occur.  Firstly control of the pelvis over the lower limb in the frontal plane is important.  A positive trendelenberg sign (pelvis dipping down as one leg is lifted from the ground) suggests weakness or lack of control over the hip abductor muscles.  Viewing the athlete from behind when running often shows excessive pelvic dip and / or wide foot stance (feet apart).  Overstriding (each step too long) coupled with a show gait cycle may also be seen.  Shorter steps and increasing cadence (using a metronome beat on a smartphone) can alter tissue loading sufficiently to modify symptoms and speed recover.  Excessive hip flexion will increase loading on the anterior tibials at heel strike compared to a reduced hip flexion and more vertical orientation of the tibia (midfoot strike).  This action will be coupled with a faster cadence as above.

Postural optimisation may also be helpful.  Although many top runners demonstrate what would normally be considered a ‘poor posture’ (round shoulders, tight hips, asymmetry of arm and / or leg action) optimising your posture may modify your symptoms.  Try to run more upright (think tall rather than slouched) and notice any glaring asymmetries such as one foot turning  out further than the other or one hip hitching.  Get a friend to video you from behind and from the side and see if changing obvious postural features affects you shin pain.  The table below shows some factors to consider.  Remember though that while postural features may help to change your symptoms there is really no good and bad posture – only one which works best for you.

 

Trigger points, fascia and acupuncture for shin splints

Trigger point massage and using a foam roller are often useful self-treatments for shin splints, to reduce pain and aid recovery.  Trigger points for anterior compartment syndrome focuses on the tibialis anterior and the extensor digitorum longus muscles. The TrP for the tibialis anterior is located approximately one-third of the way down from the knee and to the lateral side of the tibia. The thickness of the muscle means that both thumbs must be used simultaneously or a pressure tool where compression is used.  Direct compression is used and maintained for 3–10 seconds or until pain subsides.  Stretch the muscle by kneeling with the feet flat and gradually sitting back onto the heels to press the shins, ankles, and feet flat against the ground.  Use a soft mat or folded towel and take your bodyweight through your hands on the ground.

 

The long toe extensors (extensor digitorum longus (EDL) and extensor hallucis longus (EHL)) may be similarly treated. The EDL TrP is located approximately 8 cm down and slightly anterior to the head of the fibula (outer splint bone). The EHL is located at the junction of the middle of the distal thirds of the lower leg. Home stretching may be used, forcing the foot into plantarflexion and the distal toes into flexion.  Cross your legs and hold your shin down with one hand which using the other to pull your foot down and bend your toes.

For lateral compartment syndrome, the peroneus longus and peroneus brevis muscles are targeted. The TrP for peroneus longus is approximately 2–4 cm distal to the fibular head, close to the shaft of the fibular itself, while that of the peroneus brevis is located at the junction of the middle and distal third of the lower leg.

Posterior compartment syndrome and MTSS require treatment of the flexor digitorum longus (FDL) and tibialis posterior along the lower third of the posterior edge of the tibia. Where the muscle itself is stressed, the TrP is targeted on the medial border of the upper tibia, pressing the calf muscle (gastrocnemius) to the side.   Pressure is between the medial edge of the tibia and the gastrocnemius muscles.

Foam rollers may be used, especially for the more accessible tibialis anterior.  Either have your partner apply the roller, to do so yourself with the roller on the ground and you lying on your front and rolling over it.  Trigger point pressure may be applied using a tennis ball, and pressing the ball into the shin muscles is usefully carried out with the ball trapped between a wall and your leg.

Acupuncture can also be effective at releasing tightness and pain in the shin muscles, and your physiotherapist will be able to advise on this.

 

References

Batt ME, Ugalde, V., Anderson MW (1998)  A prospective controlled study of diagnostic imaging for acute shin splints.  Med Sci Sports Exerc 30(11): 1564-71

Bradshaw, C., Hislop, M., and Hutchinson, M (2007)  Shin Pain.  In Brukner, P., and Khan, K (eds)  Clinical sports medicine.  3^rd edition.  McGraw Hill.

Detmer, D.E., 1986. Chronic shin splints: classification and management of medial tibial stress syndrome. Sports Medicine 3, 436–446.

Griebert M, Needle A.R, McConnell J, Kaminski TW (2016)  Lower-leg Kinesio tape reduces rate of loading in participants with medial tibial stress syndrome.   Phys Ther Sport. 18:62-7.

Hamstra-Wright KL, Bliven KC, Bay C. (2015)  Risk factors for medial tibial stress syndrome in physically active individuals such as runners and military personnel: a systematic review and metaanalysis. Br J Sports Med.  49(6):362–369.

Hislop, M., and Tierney P (2011)  Intracompartmental pressure testing: results of an international survey of current clinical practice, highlighting the need for standardised protocols.  Br J Sports Med 45:956-958

Rajasekaran, S.  Kvinlaug, K Finnoff, J (2012)   Exertional Leg Pain in the Athlete.  Physical Medicine and Rehabilitation  4:985-1000

Steinberg, B.D., 2005. Evaluation of limb compartments with increased interstitial pressure. An improved noninvasive method for determining quantitative hardness. Journal of Biomechanics 38, 1629–1635.

Styf, J., 1989. Chronic exercise-induced pain in the anterior aspect of the lower leg. Sports Medicine 7, 331–339.