As the number of participants in recreational and competitive running continues to increase, so does the number of Chiropractic patients who need treatment for running-associated injuries. Some researchers have estimated that up to 60% of runners will experience an injury that will limit their activities.  While some of these injuries are due to actual trauma, the vast majority fall into the category of overuse syndromes. In these cases, the runner pushed beyond the capabilities of the musculoskeletal system.
Most running injuries are not due to a recent acute injury, but have developed gradually, over a period of weeks or months. These “overuse” or “misuse” conditions are due to excessive and/or repetitive motion. The end result is a microtrauma injury – the body is unable to keep up with the repair and re-strengthening needs, so the tissue begins to fail and becomes symptomatic. If it is not very painful (or if the pain is eliminated by pain-killing drugs), the runner continues to run; eventually complete failure, such as a stress fracture or ligament tear, will result. The causes of these types of injuries are often categorized into extrinsic and intrinsic sources (Table 1). 
Extrinsic factors. Causes of microtrauma injuries that are outside of the runner are often the easiest to modify, and should be addressed immediately in treatment. Extrinsic factors include: the training program (such as mileage per week, number of speed or hill workouts, recent mileage increases, and amount of rest time); running surfaces (such as asphalt, artificial track, or natural trails); and equipment (design and materials of running shoes). Modifications in the running routine (such as less mileage on more forgiving surfaces) and newer, better shoes should be introduced at the start of the rehab program for any running injury. One extrinsic source of problems that is often overlooked is the forced pronation and “environmental” leg length discrepancy due to repetitive running on a banked surface, such as along the sides of roads that have with a pronounced slant for water run-off. 
Intrinsic factors. The individual variables associated with overuse injuries are either muscle imbalances or structural alignment problems. These factors are more difficult to modify, but a good rehab program should be able to make significant progress once the problem has been identified. In fact, this is actually the most difficult part – recognizing the intrinsic source of the runner’s symptoms. A well-designed examination is necessary to investigate the structural, biomechanical, and dynamic aspects, searching for evidence of muscle imbalances, misalignments, and dysfunctions. Often there are several intrinsic factors that combine to interfere with a runner’s musculoskeletal efficiency and to limit performance. When the runner tries to push harder, the system breaks down and becomes symptomatic.
This type of categorization, however, is overly simplified. When a runner has good alignment and muscle balance, even a strenuous training program is well tolerated. Runners with biomechanical problems, however, can’t withstand even a moderate training program without developing various types of overuse injuries. A change in running surface or shoes may bring out the fact that a runner has an underlying foot or leg alignment problem that had previously gone unrecognized. In other words, the intrinsic and extrinsic factors are closely intertwined, and both contribute significantly to most running injuries.
Implementing Rehab for Runners
First the extrinsic factors must be addressed. This entails changing the training program to decrease stress, selecting different running surfaces, and upgrading the runner’s shoes. Then, all involved intrinsic factors need to be evaluated, and any problem areas are treated. This will often include support for structural alignment and biomechanical improprieties.
Muscle imbalance. Muscle imbalance inhibits normal joint function and limits the functional range of motion. Improving the flexibility of shortened and tight muscles from many miles of running is often necessary. Slow, sustained stretching must be performed regularly. Stretching is possibly most effective when the muscles are warm (at the end of a run). Stretching and gentle, passive movement of involved joints should also be initiated soon after an injury, in order to improve flexibility and prevent adhesions. If an injury is very acute, an initial period of relative rest with cryotherapy may be needed. During this period, though, exercise of the opposite leg should be encouraged. Vigorous exercise of the uninvolved contralateral leg muscles produces a neurological stimulus in the injured muscles (called the “cross-over effect”), and helps to prevent atrophy. 
Weaker or injured muscles can be safely strengthened with the use of controlled isotonic resistance exercises. The resistance can come from a machine, from weights, from elastic tubing, or just using the weight of the body. Possibly more important than the equipment used is whether the exercise is done in an open or a closed chain position. The muscles and joints of the leg form part of a closed kinetic chain when the foot is fixed (usually on the ground). Exercises performed in this position mimic the way we use the leg during most daily and sports activities, as they require the co-contraction of accessory and stabilizing muscles.
Alignment problems. Knees, hips, ankles and feet all must be in proper alignment during the repetitive striding performed during running. The arches of the foot are particularly important for providing a combined strength and flexibility to support the stress of body weight during running. Interestingly, the arches are seldom symptomatic in the earlier stages of biomechanical stress, and they are capable of tolerating extreme stresses for long periods before breaking down and failing. This strength is also a weakness, since many foot failures seem to come on suddenly, when they actually have been developing for a long time.
Biomechanics. The structures and the functioning of the foot, ankle, and knee are all exposed to greater stresses during running. The most important biomechanical action during running is the timing and amount of pronation at the foot and ankle. If there is too much pronation, or if the foot stays in pronation too long (prolonged pronation), the biomechanics of gait are altered, and running is less efficient.  Excessive pronation also increases the internal rotation of the tibia, placing additional stress on the knee.  When running is a dominant component of the recreational choices of an individual, the natural biomechanics must be able to sustain these higher forces.
A recent retrospective study looked back at the foot biomechanics of running athletes who reported recent foot and leg overuse problems, and compared them to a control group of uninjured runners.  The researchers (three M.D.s and a Ph.D. who work with many athletes and runners) wanted to determine whether excessive pronation (measured while weightbearing) correlated with the likelihood of developing various types of “overload” sports injuries. Specifically, the researchers looked at runners who had needed treatment for iliotibial band syndrome, Achilles tendinitis, stress fracture of the tibia, tibial periostitis, and plantar fascitis.
The amount of pronation during standing and while running at “regular speed” was determined by measuring the angles of the footprints of sixty six injured runners and 216 matched, uninjured control runners. The results are consistent with several other studies that have taken a slightly different approach, but have arrived at similar conclusions. The investigators found a significant correlation: Those athletes with more pronation had a much greater likelihood of having sustained one of the overuse athletic injuries. And they found that the amount of pronation seen in the static weightbearing footprint was more predictive than the footprint obtained during running. This reinforces the value of checking the alignment of our running patients’ feet in the standing position.
Shoe Inserts and Orthotics for Runners
A shoe insert made of viscoelastic material will help decrease the amount of stress on the feet, legs, and back during running.  If there is either excessive pronation or a high-arched foot, additional calcaneal and medial arch support will often need to be supplied by an orthotic.
Biomechanical efficiency. Orthotics have been found to be very useful in the long-term improvement of running biomechanics.  While there is still controversy regarding exactly how and why orthotics are so useful, [10,11] there is solid empirical evidence of their benefits to runners, for both treatment and prevention of overuse injuries. 
Shock absorption. Running exposes the joints, muscles, and connective tissues to high levels of repetitive stress. For patients with any tendency to develop overuse injuries, additional dispersion of these ground reaction forces is an important part of their treatment and rehabilitation. Even healthy young athletes who expose their knees to frequent pounding (runners, ball players, etc.) should be supplied with shock-absorbing insoles to decrease the stress transmitted from the feet into their knee and hip joints.
Overuse injuries in runners are a good example of the individual interacting strenuously with the environment. Problems can arise from either the environment (extrinsic factors) or the individual’s biomechanics (intrinsic factors). Rehabilitation needs to consider both sources of structural stress and strain, and then apply cost-effective treatments. Immediate treatment will include modifications of training and improvements in muscle balance – stretching of tight muscles and strengthening of weakened areas. For long-term improvement, biomechanical alignment problems will need to be addressed – often with the addition of custom-fitted sport orthotics. Failure to recognize these intrinsic complicating factors will result in a patient with recurring, and possibly variable complaints. A comprehensive approach to rehabilitation of running injuries provides the best hope for many years of recreational enjoyment.
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|Extrinsic Factors||Intrinsic Factors|
|training program||muscle imbalance|
|running surfaces||structural alignment|
|equipment (shoes)||biomechanical function|