sports medicine newsletter
Tibial stress injuries are one of the more frequent reasons that athletes present to my office for treatment. They are usually told by an athletic trainer that they have "shin splints" which is a nonspecific diagnosis having little clinical usefulness.
Correct Medical Terms for Shin Splints are:
- MTSS or Medial Tibial Stress Syndrome
- TSS or Tibial Stress Syndrome
- Posterior Tibial Stress Syndrome
- Anterior Tibial Stress Syndrome
The term "shin splints" describes a symptom of tibial stress injury. It is similar to saying you have a "headache" which describes the symptom not the etiology (cause). Tibial stress syndrome or medial tibial stress syndrome are terms that most authors and sports medicine experts currently favor.
Other running, jumping or cleated sports such as soccer, football, field hockey and lacrosse can contribute to MTSS cases. Approximately 12 to 13% of all runners develop MTSS (19% in female runners). It is believed that amenorrhea, disordered eating, and osteoporosis are contributing factors for increased incidence in female athlete. MTSS is the third most common sports injury behind patellofemoral pain syndrome and iliotibial band friction syndrome.
TSS can cause exquisite pain.
Risk factors for tibial stress syndrome can be divided into extrinsic (outside influences) and intrinsic categories (factors within the body). The extrinsic factors include training errors with regard to frequency, duration and intensity; surface type and inclination, and shoe type and wear.
Intrinsic factors include endocrine factors (in female athletes), structural and biomechanical abnormalities, nutritional status, and previous running and injury history. The most common factors contributing to tibial stress injury includes training errors and long-standing biomechanical abnormalities.
Athletes presenting with medial tibial stress syndrome will typically complain of aching pain in one of two locations: (lower leg) and, less commonly the upper outside portion of the tibia.
Symptoms are similar to many other overuse injuries in that athletes initially experience pain at the beginning of the activity. The pain then diminishes and often returns hours after completing the activity or the next morning. The athlete will seek medical attention when the pain starts to limit their ability to continue training. Typically, they present one to two weeks into the new season or training program.
Considering that bone remodeling starts five days after stimulation and can leave the bone in a relatively weakened state for approximately 8 weeks, it is understandable that continued athletic training during this time can lead to tibial stress fractures (TSF). The tenderness with MTSS may be exquisite and can often extend into adjacent soft tissues. It is usually confined to a 4-6 cm region at the posterior or medial margin of the middle to distal third of the tibia (lower leg). TSF, on the other hand, presents as a well localized point tenderness on the bone.
Things to do that prevent MTSS:
- Don't drive "too much, too soon": The highest incidence of bone stress injury occurs in the first month of training and corresponds to the period of bone remodeling. Allowing the bones time to remodel slowly during the initial phase of training will limit the incidence of tibial stress syndrome.
- Keep your eye on the road: A level, uniform surface of moderate firmness is best for minimizing injury risk. Running on sand, road shoulders or on uneven terrain causes overworking of leg muscles.
- Monitor your shocks: Studies have shown that a running shoe loses more than 60% of its shock absorbing qualities after 250 miles. The treads on the shoes may look fine but the inability of the shoe to prevent injury is not.
- Balance you tires: Address the biomechanical abnormalities and structural malalignments with functional orthoses dispensed by a Doctor of Podiatric Medicine & Surgery who specializes in Sports Biomechanics.
There is a growing body of evidence that suggests that MTSS like TSF is a "bone stress reaction" caused by chronic repetitive loads to induce bone bending forces. It is important to note that maximal tibial bending occurs at its narrowest width at the middle to distal third of the tibia which corresponds to the anatomic site of MTSS.
When the tibia experiences this chronic repetitive bending strain it is "stimulated" to deposit new bone at this level. Increased bone marrow density often follows. Although it is not universally accepted that MTSS is simply a mild form of, or a precursor to TSF, this author believes that this is true due to extensive work with Marine Recruits. If strain continues in this area for an extended period of time, it is possible for micro-fractures (or stress fractures) to form.
An analogy that can be given is similar to building a skyscraper on a city block that is occupied by a dilapidated building. In order to lay the foundation and pilings to support a larger structure the old building must be torn down. Bones react in the same manner. The body recognizes increased stressors and the need for stronger bone at the narrowest point and site of tibial bending. Before the bone can lie down new, stronger bone, the older bone must be "excavated" from the area. It is during this period of bone resorption (a weakened state) that a stress fracture can occur if the activity is persists.
Figure 1: Common sites of pain from those who
suffer from "shin splints" which is actually referred
to as Tibial Stress Syndrome by medical experts.
Recognizing abnormal biomechanical/structural contributions to the development of tibial stress injuries and other exercise-induced leg conditions is paramount in the treatment of athletes.
Tibial stress syndrome can occur both in the "high arched" (pronated) and low arched (supinated) athlete.Over pronation (flattening of the arch) can cause overworking of the posterior tibial tendon and posterior flexors at their origin in posterior aspect of the leg. This may lead to micro tears and inflammation along the muscular attachment to the tibia due to "bone bending forces" described above. It is often referred to as Posterior Tibial Stress Syndrome. See Figure 1 for illustration of posterior and anterior tibial stress syndrome sites of pain. Anterior Tibial Stress Syndrome can occur due to the factors below. Anterior Tibial Stress Syndrome (ATSS) occurs due to a weakened anterior group and a stronger posterior group of muscles in the lower leg. It is usually seen bilaterally. ATSS usually presents in athletes who are aggressive initially in their training program, do excessive downhill running or participate in sports that have abrupt starts and stops like baseball. Muscle imbalance can occur in the high arched, cavus foot as well as the low arched, pronated foot. In the pronated foot, the posterior group "over works" in attempt to raise the arch during propulsion therefore "outperforming" the anterior group.
In a high arched, cavus foot, the posterior flexor group is generally stronger than the anterior group due to a phenomenon called flexor substitution. The high arched foot has a double whammy in regards to it's predisposition for Tibial Stress Syndromes. Along with having this muscle imbalance between the anterior and posterior muscle groups, the cavus or high arched foot is also a poor shock absorber leading to additional stressors on the tibia.
Correcting abnormal biomechanics is critical to MTSS treatment. If the pathomechanical issues associated with tibial stress syndrome are ignored, reoccurrence is inevitable. Prescription functional orthotics, custom made to the biomechanical measurements of the athlete's foot, is by and far the best way to cure MTSS as well as prevent future injury.
This can be accomplished by a combination of rest, immobilization through tapings, ace wraps or neoprene sleeves, icing, oral medications such as anti-inflammatories, alternative or cyclic training, change of shoe gear and orthotic devices.
