Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Etiology of Running Injuries

The etiology of running injuries is multifactorial. Factors may be extrinsic or intrinsic.

Running

Running is an effective way to exercise large muscle groups and has a documented effect in the preservation of health and in the prevention of cardiovascular problems. However, it is a potentially harmful activity, and running injuries are common—although 2–2.5 times less frequent than injuries from other sports. The overall yearly incidence rate for running injuries is about 37–56%. The incidence of all running injuries ranges from 3.6 to 5.5 injuries per 1000 hours of running. For competitive athletes, the range is 2.5–5.8 injuries per 1000 hours of running, depending on the specialization.

The examining physician must remember that most runners are dedicated to their running activity. Runners usually complain about problems associated with running, but they can often participate in sports activities, such as cycling, swimming, and crosscountry skiing, that involve lower levels of repetitive stress.

Running should be differentiated from sprinting, which is characterized by such factors as increased velocity, decreased shock absorption in early stance, and initial ground contact with the toe. Approximately 75–80% of runners have initial heel contact at distance running, and the remaining 20–25% have midfootforefoot contact.

Runners’ problems occur because of the repetitive stress that running places on the lower extremities. The ground reaction force at the time of the midstance phase in running is equivalent to a vertical force ranging from 1.5 to 5 times body weight. A man running with stride length of 1.6m (4.5ft) will take approximately 1175 steps per mile. Considering an impact of 250% of the body weight (68 kg; 150 lb), the runner absorbs at ground contact a total of 220 tons, or 110 tons on each foot per mile. At a pace of 7 minutes per mile, stance time is approximately 0.2 second, which translates into approximately 5100 contacts during 1 hour of running. Considering those huge loads on the tissues, it is clear that even small biomechanical abnormalities can result in a significant concentration of stress and load.

Extrinsic factors are present in 60–80% of reported injuries in runners. The most common of these are training errors.

Training errors

The most common errors are sudden changes in the running activity, such as increased distance or intensity. An example of this is a novice runner starting to run regularly, or an injured runner returning to running, who may attempt too much, too soon, resulting in an overuse reaction. Specific training errors include:

– persistent high-intensity training without taking easy days with lower intensity;

– sudden increases in distance and intensity without adequate rest;

– single severe training or competitive sessions, such as marathon or other long-distance events;

– repetitive hill training.

The injury rate is proportional both to the absolute level of training and to changes in the relative intensity and volume of training. The total weekly distance run is significantly associated with injury. The relationship between running speed and injury risk remains unclear. Running experience has not been proven to be significantly related to running injuries.

Running terrain

Too much downhill running can cause problems in the knee joints, because the body weight is mainly behind the knee’s vertical axis, which requires high forces on the quadriceps muscles to protect the knee. In downhill running there are increases in knee flexion, net extensor moment, patellofemoral forces, power absorption of the knee extensors, and contraction of the knee extensors. Running up and down hills has been reported to produce injuries. There is no association between the rate of running injuries and terrain. Downhill running can produce pain symptoms from injury syndromes such as patellofemoral pain and iliotibial band friction syndromes. Too much uphill running can cause problems such as Achilles peritenonitis and plantar fasciitis.

Running surfaces

The running surface may be of importance. Certain surfaces may triple or quadruple the frequency of injuries in selected sports activities. Running on hard surfaces such as asphalt or concrete, which causes mechanical shock and thereby overloads joints and tendons, may be associated with a greater incidence of running injuries. Running on too soft a surface allows hypermobility of the joints, fatigues the muscles, and may cause overuse injuries. Wooden chips provide an excellent surface.

Running on uneven or artificial surfaces or on slippery roads can also cause overuse injuries. Running on a banked surface, or on the camber of a road in one direction, is apt to cause an abnormal stress on one side of the body. The result is a functional leg-length discrepancy, which may result in iliotibial band friction syndrome or trochanteric bursitis.

Running shoes

A poor choice in sports shoes can be responsible for the development of sports injuries, because shoes can alter forces in specific anatomic structures by more than 100%. Sports shoes may also influence the site, type, and frequency of sports injuries. However, a study of three popular brands of well-constructed running shoes showed no difference in injury incidence.Inadequate or worn-out shoes can cause increased stress and overuse. It is not acceptable to use tennis or basketball shoes during a regular running program. These shoes do not have the appropriate features to protect the runner from injuries. Improvements in footwear have led to a decrease in injuries of the foot and lower leg as a whole, but there have been increases in certain injuries, such as iliotibial band friction syndrome.

The shock-absorbing capacity of running shoes is considered important in injury prevention. Shock absorption can be increased by shoes fitting well. Shock-absorbing qualities are reduced in wet shoes, and also with wear, being reduced by 30–50% after only 400 km (250 miles) of running.

Technique

Running technique varies from one sport to another. Long-distance runners generally strike first with the heel, followed by the toe, while short-distance runners tend to be either midfoot strikers or run on their toes only. The most common technique faults are striking too hard with the heel, and running flatfooted. These can result in overuse injuries. Repeated incorrect running or jumping techniques nearly always result in overuse injuries.

Intrinsic factors

Intrinsic (body-related) factors can be divided into basic, primary, and secondary (acquired). Basic intrinsic factors include sex, age, growth, weight, and height. Important primary intrinsic factors are malalignments, leg-length discrepancy, muscle imbalance and inadequate strength, and poor flexibility and neuromuscular coordination. Secondary acquired factors, such as kinetic chain dysfunctions and previous injuries, are also important.

Basic intrinsic factors

Sex: sex and age are not important predictors of running injuries in general. Women have a weaker musculoskeletal system, 25% less muscle mass per body weight, less bone density, and a wider pelvis and more mobile joints than men. These factors can predispose women to specific injuries, such as pelvic stress fractures and patellofemoral pain syndrome. It is also known that menstrual irregularities constitute a risk factor for certain overuse injuries such as stress fractures. Overall, however, there is not an increased risk for running injuries in women.

Age: changes in the musculoskeletal system associated with aging include decreases in bone density, muscle strength, water content, metabolic activity, and collagen in tendons. Elderly people have greater degenerative changes in their tissues, with a decreased ability for shock absorption and, thereby, an increased risk for injuries. People with more than 30–40 years of extensive running experience did not have an increased incidence of osteoarthritis of the hip. There is no increased incidence of running injuries with age as a primary factor. This could be because the elderly run for enjoyment, at a slower pace and over shorter distances, and because they are more careful in general.

Growth:adolescents aged 12–15 years often have an imbalance between lever arm muscle strength, tightness, joint mobility, and coordination. Muscle—tendon units are relatively shortened at this age. Some diagnoses are age- and growth-dependent, such as Osgood-Schlatter disease, apophysitis injuries, and certain avulsion fractures. After the growth spurt, adolescents usually need a more flexible training program, including stretching. 

although being overweight often is considered to be a potential problem for long-distance runners, no relationship has been found between body weight and running injuries. The development of knee and hip symptoms and osteoarthritis is, to some extent, associated with being overweight, as running may further accelerate the osteoarthritic process. Height is not related to running injury incidence.

Primary intrinsic factors 

Malalignments in the foot can be simplistically divided into pes planus (flat foot) and pes cavus (claw foot), each of which occurs in approximately 20% of the population. Pes planus results in an excessive pronation through midstance. Excessive pronation can be physiologic, but it can also be secondary to tibial varum (leg directed inwards) of more than 10°, functional equinus (foot directed, talar varus, and/or forefoot supination. Many good runners have a mild genu varum. There may be a low likelihood of injury if the total varus is less than 8°, and an increased incidence in runningrelated injuries if the varus is greater than 18°.Different malalignments can be combined. The ‘miserable malalignment’ syndrome which can be seen in some runners, combines femoral neck anteversion (forward angling) with internal rotation of the hip and genu varum (with or without knee hyperextension), squinting patellae, excessive Q angle, tibial varum, functional equinus, and compensatory foot pronation. A miserable malalignment syndrome can cause such problems with regular running that it is reasonable to say that some people with this malalignment simply should not be running long distances.Cavus feet are also associated with running injuries. Cavus feet were found to be present in about 20% of a group of injured runners. Athletes with cavus feet have decreased motion of the subtalar joints, with resulting decreased flexibility of the midfoot and excessively weighted rear foot varus. At foot strike, the heel remains in varus, the longitudinal arch is maintained, and the foot does not unlock. The tibia remains in external rotation, and the net result is increased stress because the arch continues to be rigid through the midstance phase of running. With a reduction in internal tibia rotation, stress is passed through the lateral foot and knee, resulting in injuries such as iliotibial band friction syndrome, trochanteric bursitis, stress fractures, Achilles tendinitis, peroneal muscle strain, plantar fasciitis, and metatarsalgia, which are common in runners with cavus feet.

Structural variations can predispose to injury. A prominent posterior calcaneus can cause Achilles tendon and/or bursa problems. A large os trigonum or a prominent posterior talar beak can cause posterolateral ankle pain. Tarsal coalition of different kinds can cause abnormal painful motion. An accessory navicular can cause medial midfoot pain

Good flexibility is stressed by many as important in the prevention of running injuries. Running itself causes tightness of hamstrings and calf muscles. These regional inflexibilities can contribute to injury. There seems to be no association between stretching habits and the incidence of injury. 

Muscle strength: muscles stabilize the lower extremity and attenuate the forces and impact of running. Because of the important role of muscles in both stability and shock absorption, muscle weakness may predispose to stress fractures.

Neuromuscular coordination:  a breakdown in balance and motor control can predispose a runner to injury. Any deficit in proprioceptive capacity may lead to functional instability that could make the athlete more prone to injury.

Ligamentous laxity: generalized laxity of the ligaments in excessive pronation can increase the risk of injury.

Secondary or acquired factors

With the kinetic chain the lower extremity is seen as a series of mobile segments and linkages that allow forward propulsion during gait. The kinetic chain is closed when the foot is in contact with the surface in stance phase and is open when the foot is off the ground in the swing phase. Anything that interferes with the normal progression and mechanics of force transfer can lead to alterations in gait and compensatory changes in the motion at other sites in the chain. In patients with recurrent and previous injuries, it is especially important to focus on the dysfunction of the kinetic chain. Because kinetic chain function is very complicated in nature, it is frequently overlooked as an etiology of running injuries.

The role of secondary or acquired dysfunction in causing injury remains controversial. These dysfunctions usually result from hyper- or hypomobility of a segment of the kinetic chain after an injury. Any dysfunction in the kinetic chain can lead to compensatory alterations in stance and gait that, in turn, can lead to tissue microtrauma, breakdown, and overt injury.

Mechanical dysfunction: changes in the position and motion of the sacroiliac joint are fairly common. Although the sacroiliac joint is usually stable, with little motion, it has been claimed that motion can occur with anterior subluxation and rotation and can lead to asymmetry of the pelvic ring structure. This dysfunction is characterized by locking or hypomobility at the involved sacroiliac joint. The main symptom, pain, is usually localized to the sacroiliac joint but may also radiate to the buttocks and the groin region. In order to identify sacroiliac joint dysfunction, one must be aware of its existence and understand the biomechanics involved. A high index of suspicion should be present when treating patients with recurrent injury. 

Previous injuries: most injuries heal sooner or later, but they can leave a residual scar in the tissue. This scar may have an elasticity different from that of normal tissue and can create a weak area with an increased risk of injury. Multiple and recurrent injuries may be indicative of kinetic chain dysfunction. Previous injuries can lead to fibrosis, with adhesions and limited joint motion and function. Long-standing joint injuries resulting in chronic instability, or even the slightest effusion, can result in a reflex inhibition of the muscles and secondary alteration of gait. Restricted motion of knee, ankle, or subtalar joints will increase stresses on other areas. Joint instability will result in muscle hypotrophy and increased compensatory stress on other structures.

Diagnosis of running injuries

The precise diagnosis of running injuries is often a challenge. An understanding of the injury mechanism and of different diagnostic options is important. Physicians often focus on the injury site when treating overuse running injuries. Any injury should, however, be regarded as a manifestation of dysfunction in the kinetic chain, and the entire chain must be examined to rule out any asymptomatic underlying injury or dysfunction. This approach is especially important in individuals with previous or recurrent injuries.

History

The history of running injuries is important, because it forms the basis on which a diagnosis is made. The physician should be aware of the demands and biomechanics of running. It is important to analyze the entire running program, including changes in distance and training conditions. The shoes the runner has been wearing and the use of orthotic devices should also be discussed.

Physical examination

An evaluation of the entire lower extremity and back can be carried out with the runner in standing, sitting, prone, and supine positions. The whole lower extremity should be carefully examined for asymmetries of both static and dynamic alignment and function. Any biomechanical imbalance in the foot or the lower extremity should be noted. The dynamic examination can be direct and should include gait, functional foot movements, patellar tracking, leg-length evaluation, and functional sacroiliac joint tests. The dynamic evaluation can also be indirect—for example, the runner’s shoes can be examined for wear patterns. A full functional examination should include testing of the various linkages of the kinetic chain and running on a treadmill could be helpful.

Radiographs are sometimes of value. Indications for their use include suspicion of an arthritic joint or stress fractures. A bone scan is positive 2–8 days after the onset of stress fracture symptoms. Magnetic resonance imaging is a noninvasive imaging technique that provides excellent soft tissue contrast in multiple planes without exposing the patient to ionized radiation. It can provide a detailed assessment of the intrinsic abnormalities in tendons. Ultrasound evaluations have been shown to be valuable in the diagnosis of ‘jumper’s knee’, meniscus lesions, and Achilles tendon lesions. The development of arthroscopy has also been of great importance in the diagnosis and treatment of injuries to the knee and ankle.

Running overuse injuries constitute a diagnostic problem because the symptoms of these injuries are often diffuse and uncharacteristic. The diagnosis of a runner’s injury rests with the identification not only of the affected tissues but also the underlying predisposing conditions.

Principles of treatment

When treating running injuries, it is important to treat not only symptoms of the injury, but also the cause of the injury. It is, therefore, important to determine the primary problem and any secondary problems that may have resulted. Identification of kinetic chain dysfunctions is important. A correct diagnosis is the base for a successful treatment.

The cause of injury

Training routines must be checked, and training errors identified. An effective biomechanical strategy to reduce load and stress on the locomotive system can be:

– alter the movement (change the running style);

– alter the surface (run on a soft surface rather than a hard surface);

– change the shoe;

– diminish the frequency of repetition of movement (reduce the distance run).

Normal alignment and symmetry of the kinetic chain must be restored. Orthoses—rigid, semiflexible, or soft—may be the treatment of choice when malalignment or asymmetries are present. An orthotic device can significantly affect the amount of maximum pronation, time to maximum pronation, maximum pronation velocity, period of pronation, and movement of rear foot angle in the first 10° of foot contact. Undercorrection is common, and orthoses rarely provide the exact hindfoot and forefoot posting necessary to ensure a neutral subtalar joint. The common approach, to post the subtalar position to the maximum of 4° of varus, will provide adequate control. Despite their popularity, the use of orthotic devices is still controversial, and there are failures with this type of treatment. These failures may be caused by neglecting to adjust or change the orthotic devices as needed from time to time. No prospective scientific studies are available to show the effects of these devices. We have found that more than 80% of runners were satisfied with their orthotic treatment and experienced improvement after 1 year of wearing their orthosis regularly. Most runners adjusted to their orthosis after only 2–3 weeks, which is a much shorter time than had been anticipated. It is important to use well-constructed running shoes, to provide cushioning support and friction. Running shoes give a maximum point of pronation, which occurs significantly later when barefoot than when wearing a running shoe. Shock absorption can be increased by well-fitting shoes. A runner’s shoe should be a stable shoe with optimal shock absorption in the sole or insole and a well-fitted heel counter that is rigid around the heel pad.

With very few exceptions, stretching exercises should always be used by runners, who, in general, have very tight muscles and tendons. If the athlete is very flexible, strengthening exercises may be indicated. Adequate muscle strength, balance, flexibility, and coordination are essential, as are normal alignment, mobility, and symmetry of the kinetic chain.

Surgical correction may be indicated for some malalignments.

The symptoms

When treating running injuries, it is important to have an exact diagnosis before a specific treatment is initiated. The stage of healing should determine the mode of treatment to be used. Treatment should start as early as possible. Initially, pain and inflammation are treated with rest, avoidance of weightbearing, elevation, cryotherapy, compression, immobilization, and protection. Crutches are often indicated. Anti-inflammatory medication can be helpful. Heat, which increases the extensibility of collagen in connective tissue, decreases joint stiffness, and gives pain relief, should be used after 24–48 hours. Local heat can be generated by heat retainers.

Exercises should begin as early as possible. The initial program should be prescribed according to the slow progression principle, with a gradual increase of the load within the limits of pain. Because strength training alone has a negative effect on joint flexibility, it should be counteracted by flexibility training, including stretching. Crosscountry skiing, swimming, and cycling are valuable alternatives to maintain a good conditioning level if running is not possible. Pool running can also be effective.

Surgery should be avoided until conservative therapy has failed. Excision of scar and degenerative tissue secondary to delayed healing in tendons, such as chronic partial tears to the Achilles tendon and adductor longus injuries, has shown good results. Although the postoperative rehabilitation period may be long, the overall results are good.

Type and location of running injuries

Running injuries can involve most of the tissues in the body, including muscle, tendon, fascia, bone, bursae, nerves, and cartilage. The structures reported to be most commonly involved in overuse injuries were muscle and fascia, 27.2%; tendon and muscle insertion, 21.6%; joint surfaces, 15.9%; tendon and tendon sheath, 15.1%; bursae, bones, and nerves, 21.4%. The knee—the most common site of injury— was involved in 48% of all running injuries, followed by the lower leg, 20.4%; foot, 17.2%; hips, 6.0%; upper leg/thigh, 4.2%; and lower back, 4.1%.

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