Br J Sp Med 1993; 27(1)

Review

Overuse injury and growing bones: the young athlete*at risk*David F. Gerrard MB ChBOtago University, School of Physical Education, Dunedin, New Zealand

Increasing numbers of children are becoming involved incompetitive sport. International trends in pre-adolescentsports participation are mirrored in New Zealand, wherepromising young athletes are being exposed to high-intensity training from an earlier age. As a consequence,overuse injuries which were traditionally described inmore mature athletes are now becoming recognized inpre-adolescents. The immature musculoskeletal system isless able to cope with repetitive biomechanical stress.Sites of overuse injury reflect the sites of rapid musculo-skeletal development. It therefore behoves all medicalpractitioners, but particularly those in primary care, to beaware of the young athlete at risk. Inherent in thepresentation of such musculoskeletal insult there oftenlurks an over-enthusiastic parent. We are all wellreminded of the covert pressures adults may bring to bearupon children. Psychological, as well as physical injuryoften results.

Keywords: Children, sport, epiphysis,medicine

injury, sports

Over the past two decades in New Zealand, anincreasing number of children have joined thecompetitive sporting ranks1. Most authorities agreethat such physical pursuits are both beneficial andnecessary for normal development, provided thatsport can be kept as safe as possible and enjoyable toparticipants2The Accident Compensation Corporation participa-

tion rates survey (1985), revealed that 503 000 NewZealand children aged between 5 and 19 years playedorganized winter sport. The Life in New ZealandStudy, an initiative of the Hillary Commission (1990),stated that there was a dearth of information availableon the participation of children in physical activity.The data presented in the study highlighted a genderpreference for certain sports (particularly the tradi-tional winter sports of netball, rugby and soccer). Ofinterest was the high involvement of 11-13-year-oldchildren in non-structured activities such as skate-

T COOL

*A paper delivered to the Royal N.Z. College of GeneralPractitioners Conference, Rotorua, July 1992Address for correspondence: Dr D. F. Gerrard, Otago University,School of Physical Education, Dunedin, New Zealand

(© 1993 Butterworth-Heinemann Ltd0306-3674/93/010014-05

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boarding. The popular choices of activity and thenumbers participating in physical activity betweenthe ages of 5 and 15 years are illustrated in Figure 1.

In 1988 (again as the result of the influence of theHillary Commission), this country saw the launch ofKiwiSport, a widely applauded initiative whichprovided the stimulation of modified sport for allchildren under 12 years of age. In all, 22 sports werecatered for under a system of simplified rules, whichallowed children of all abilities to participate on equalterms. There was a clear emphasis against competi-tion and a strong emphasis upon enjoyment and skillacquisition.The success of KiwiSport highlights the importance

of introducing pleasure and safety into children'ssport. Inherent in this is the implication that manyyoung athletes are having too much too soon. Thereare compelling psychological as well as physiologicalreasons for us to view children's sport both broadlyand with wisdom.Given this country's enthusiasm for sport and our

international success, the 'catch them young' philo-sophy3 has its adherents in enthusiastic coaches andover-anxious parents. Such vigorous talent identifica-tion more often results in psychologically depletedstars (ready to retire in their 'teens), or chronicallydebilitated victims of overuse injury.The International Federation of Sports Medicine

(FIMS) states4 that intensive training of children hasno physiological or educational justification, andbelieves that diversity of movement and all-roundphysical conditioning should have priority over laterspecialization. Whereas play and traditional gamesare involuntary and unstructured, the prime featureof organized sport is the use of systematic repetitivetraining to improve fitness and develop specialistskills. The New Zealand Federation of Sports Medi-cine endorses the sentiments of its parent interna-tional body by promoting the values of broadnon-specialized sports participation for pre-adolescents.

Overuse injury in young athletes: D. F. Gerrard

Injury and incidenceThere are no good epidemiological data available inNew Zealand to compare the rates of injuries in sportwith those of free play activities. In the USA, theboom in organized sport for children and adolescentshas been matched by an increase in injuries to areasof active musculoskeletal development' 6.

Injury is the result of two distinct biomechanisms.The first is the result of a single violent impact, thesecond the end product of many repetitive minorinsults. Spontaneous, unstructured activities maywell expose children to the major forces of impact andviolence in the same way that fractures and disloca-tions result from organized body contact sport. Butthe minor, individually insignificant stresses whichaccumulate to produce overuse syndromes are moreobviously linked to established sporting patterns. Ithas become clear, that the young athlete is at riskfrom microtrauma which may be sports specific.

Reports of 6-year-old marathoners, 8-year-oldswimmers churning out 20km per day in the pool,young tennis players hitting hundreds of serves andvolleys, and young gymnasts spending hours per-fecting their routines are recorded in the sportsmedical literature7.The FIMS statement4 confirms the establishment of

a new genre of paediatric sports injury. Overuseinjuries such as these were totally unknown inchildren until the advent of repetitive sports training.Today there is a growing list of common sites of

childhood sports injury, each known either by itseponym or the sport with which it is associated.Quite clearly, the pathogenesis of such injuries islinked to the unique and vulnerable phase ofmusculoskeletal development of childhood. Thepresence of areas of bone-cartilage maturation andthe relative weakness of growing bones comparedwith ligaments and tendons are significant factors.

Musculoskeletal growth

Cricket

Cycling

Netbal

Swimming

Tennis

9 20 40

Figure 1. Children's physical activity. Participation rates ofNew Zealand children between the ages of 5 and 15 years.*, boys; 0 girls. Reproduced from Life in New ZealandSurvey with permission (©) Hillary Commission 1990

Conventional medical wisdom should remind us thatchildren are simply not little adults. This fact is oftenignored by enthusiastic sports administrators,coaches and parents who coax and cajole theirpre-adolescent proteges to swifter, higher, strongercompetitive levels (Citius, altius, fortius).The skeletal uniqueness of children is the essence

of their physical vulnerability to repetitious micro-trauma. Sites of vigorous musculoskeletal develop-ment in long bones and their musculotendinousattachments are the specific areas of potential sportsinjury (Figure 2).The growth process of bone is well understood.

Children are developmentally unique in that theypossess a physis or growth plate in the ends of

D

growing long bones. This proliferating plate ofcartilage separates the epiphysis (the portion of bonebetween the physis and the joint surface) from themetaphysis (or remainder of the long bone). The socalled epiphyseal plate closure signals fusion ofprimary and secondary centres of ossification and isrecognized clinically as bony maturation. However, ifinjury occurs before epiphyseal plate closure then

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Overuse injury in young athletes: D. F. Gerrard

Growth plate

Epiphysis(articular cartilage)

Figure 2. Musculoskeletal growth - sites of potentialoveruse injury

significant, permanent growth disturbance is likely.Further areas of active growth cartilage exist wheremuscles and tendons attach to bone. These sites aretermed apophyses, vulnerable to repetitive tractionforces and often implicated in pre-adolescent overuseinjury.

Another significant factor in the genesis of child-hood injury is the growth process itself'0. Musculo-tendinous units which span growing bones and jointsbecome progressively taut. As a direct consequence,there is a loss of flexibility and an increased potentialfor traction apophysitis from vigorous or repetitivestress.

In summary, it is evident that the presence ofgrowth cartilage at either the epiphyseal plate, thearticular surface of the apophysis predisposes thesesites to injury. Asynchronous development of boneand soft tissue provides significant additional risk tothe pre-adolescent who, during periods of rapidgrowth ('spurt') loses flexibility. During such de-velopmental phases it is clinically sensible to reducethe training load imposed upon young athletes.

Sites of injuryNumerous sites of potential overuse injury aredescribed. Many bear the eponym of the clinician(s)credited with the original description. Others arenamed for the sport or activity with which they arecommonly associated (Table 1). Children's overuseinjuries include bursitis, tendonitis, apophysitis oftendon insertions, stress fractures of long bones and,in certain cases, osteochondral injuries of the jointsurface'. The 'Little League elbow', breaststroker'sknee, swimmer's shoulder and jumper's knee reflect

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Overuse injury in young athletes: D. F. Gerrard

Table 1. Common sites of overuse injury, their associated sports and their popular (eponymous) names8'9

Site Associated sports Eponym

Tibial tubercle Jumping, sprinting, skiing, weight training, soccer, horse riding Osgood-Schiatter's diseasePatella (inferior pole) Soccer, rugby, jumping, skiing, sprinting, dancing Sinding-Larsen-johansson syndromeCalcaneus Running, sprinting, aerobics, soccer, rugby, fencing, dancing Sever's diseaseNavicular Sprinting, running, aerobics, dancing KohIer's diseaseOlecranon javelin/throwing sports, tennis, gymnastics, weightlifting Palmer's diseaseLunate Tennis, throwing sports, martial arts Keinbock's diseaseThoracic spine Rugby, weightlifting, gymnastics, swimming (butterfly) Scheuermann's diseaseSecond metatarsal head Dancing, martial arts ('kicking' sports) Freiberg's diseaseThird metatarsal head As for second metatarsal injury Kohler's II

distinct athletic associations. They may be devastat-ing injuries to the pre-adolescent athlete (or hisparents), but when recognized early and diagnosedaccurately they respond well to conservative treat-ment and rest.

Back painIn a number of activities, but particularly those whichdemand vigorous repetitive hyperextension of thelumbar spine, low back pain may present. Butterflyswimming, gymnastics and cricket fast bowling arethree common examples. Rapid growth of thevertebral bodies is not matched by an increase in thedorsal, tethering soft tissue structures. As a consequ-ence many young athletes have an increased lumbarlordosis. Given the additional stress of repeatedhyperextension, children often present with chroniclow back ache.Most investigators agree that the most common

causes of such pain are hyperlordotic mechanical lowback pain, stress fracture of the pars interarticularis(spondylolysis) or a disc protrusion11. Slightly morecephalic pain (thoracolumbar) suggests Scheuer-mann's disease which appears to be linked torepetitive sporting action. Among the more success-ful methods of treatment in cases of athletic low backpain are the physiotherapeutic measures of antilor-dotic exercises, hamstring flexibility and pelvicflexion exercises.

Hip and pelvic painA stable hip and pelvis presides over many athleticactivities. In young gymnasts or dancers, hip painwith or without dysfunction is frequently described.Having excluded (radiologically) such problems asslipping of the upper femoral epiphysis or Perthes'osteochondritis of the femoral head, apophysitis atthe site of major muscle attachments is a commoncause of hip or pelvic pain. There is often focaltenderness in the region of the iliac crest or iliacspines which is accentuated by resisted movement.

Knee painAcknowledged as a common site for impact (macro-trauma) the knee joint is also vulnerable to overuse

injury in children. Anterior knee pain may belocalized to the patella, its lower pole or the patellartendon insertion into the tibia. If pain is focal andassociated with swelling over the tibial tubercle, theclinical diagnosis is that of Osgood-Schlatter disease.Radiological confirmation is mandatory, as is restfrom violent excursions of the knee extensor mechan-ism.

Retropatellar knee pain, aggravated by runningand descending stairs, is strongly suggestive ofmaltracking of the patella and consequent irritation ofthe patellofemoral compartment. If the focus of painis at the lower pole of the patella, a tractionapophysitis (Sinding-Larsen-Johansson disease) islikely. Radiographs sometimes demonstrate smallbony avulsions which are thought to represent extraossification centres. Such overuse trauma is bestmanaged with 'active rest' (offering alternativephysical options which do not stress the injured part)and frequent clinical review by doctor and/orphysiotherapist.

Non-specific knee pain in the young athlete mustalways be treated with respect. Of the significantconditions to exclude, including referred pain fromhip disease, osteochondritis dissecans is important. Ifan osteochondral fragment becomes separated, thereis a significant risk of joint dysfunction and obviouslythe long-term risk of premature joint degeneration. Insuch cases a radiograph is mandatory. Of clinicalsignificance is the fact that the presence of osteochon-dritis dissecans in one site is often linked (through apresumed form of inherited epiphyseal dysplasia)with the same condition in other sites12.

Foot and ankle painHeel pain, often described in children playing fieldsports such as hockey and soccer, is usually worseafter activity. Tenderness over the os calcis at theinsertion of the tendo Achillis is often associated withSever's apophysitis. An accompanying tight posteriorcompartment (gastrocnemius-soleus mechanism) isrecognized as part of the developmental cause(reflecting the asynchronous bone versus soft tissuegrowth rate).

Stress fractures of the os calcis, tarsals and thenavicular must be borne in mind when considering

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Overuse injury in young athletes: D. F. Gerrard

the causes of foot pain in young athletes. The returnfrom routine radiographs is often small and suchtechniques as bone scanning and magnetic resonanceimaging (MRI) are being vaunted as the mostproductive diagnostic aids13.

Shoulder pain

Overuse injuries in swimming and throwing eventsreflect a repetitious pattern of impingement betweenthe humeral head and its rotator cuff attachments(especially supraspinatus) under the coracoacromialarch.The so called swimmers' shoulder has attracted

considerable interest given that thousands of gleno-humeral articulations in young performers oftenresults in local, inhibiting pain and dysfunction.Swimmers are found to be weak in external shoulderrotation compared to internal rotation, and thismuscle imbalance is thought to be of aetiologicalimportance. Together with the previously described'impingement' and the relative avascularity of thesupraspinatus tendon near its insertion, thepathogenesis of swimmers' shoulder is becomingunderstood. Treatment suggestions range from restto biomechanical assessment, physiotherapy modali-ties, non-steroidal anti-inflammatories and, in somerecalcitrant cases, surgical decompression of thestructures beneath the coracoacromial arch.

Typical overuse injuries in adults involve bone(stress fractures) tendons and fascia. However, theuniqueness of the young athlete's musculoskeletalsystem predisposes it to special injury risks. Not onlyis the young skeleton growing rapidly, but if offerssupport to developing soft tissues. It follows that themost rapidly developing areas of the child's skeletonare the most vulnerable.Growth cartilage is present at three important sites:

at the growth plate itself (physis); at the joint surfacein the form of articular cartilage; and at the site ofmajor muscle-tendon insertions (the apophyses).Insult to these areas of tissue interface results in thetypical pre-adolescent injuries of sport. Indiscrimin-ate, repetitive training regimens are associated withpathology at tendinous junctions, tendoperiostealattachments and immature epiphyseal plates.

It is the responsibility of the coach, administratorand parent to acknowledge the particular susceptibil-ity of young athletes to injury. Medical practitioners,physiotherapists and physical educators have a

clinical responsibility to advise, guide and monitor.In accepting that there are numerous factors whichcontribute to injury a multidisciplinary approach tochildren in sport will address both the externalprecipitants (footwear, surfaces, weight training) andthe intrinsic factors (growth, muscle-tendon imba-lance, flexibility) unique to the immature athlete.

Finally, we must remember that for children'scompetitive sport to have positive developmentalassociations, safety and pleasure must be integralelements. The question of skill and the developmentof social strategies for interaction are importantreasons for children to play sport. Those withobvious talent will emerge and if such qualities arenurtured, they will become the stars of the future.The spirit of the 'catch them young' philosophy istainted by the psychological and physical casualtieswhich result from youngsters being pushed too hardtoo soon.

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young athlete at risk.Overuse injury and growing bones: the

D F Gerrard

doi: 10.1136/bjsm.27.1.141993 27: 14-18 Br J Sports Med

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