R. Peter Welsh

Patellofemoral Arthralgia,Overuse Syndromes of the Knee,and Chondromalacia PatellaSUMMARYPatellofemoral arthralgia is a very commonsyndrome affecting athletes. Most often,examination fails to define true pathology.Conservative treatment, an active exerciseprogram, and sports may be undertakenwithout harm to the knee. The patellofemoralarthralgia syndrome must be differentiatedfrom true chondromalacia patella, where thereis actual degeneration of the patella's articularcartilage, and from other sources of internalderangement such as meniscal disease orosteochondral lesions. Careful attention to thehistory of onset, and provoking activities suchas climbing stairs, kneeling, and crouching,will allow the physician to recognizepatellofemoral arthralgia. Other commonoveruse syndromes also should be looked for,and differentiated from problems due to trueinternal derangement. (Can Fam Physician1985; 31:573-576).

SOMMAIRELes athletes se plaignent tres souvent d'arthralgiefemoro-patellaire. Le plus souvent, 1'examen nepermet pas de preciser la vraie pathologie. On peutentreprendre un traitement conservateur, unprogramme d'exercices actifs et certains sports sanseffet dommageable au genou. I1 faut differencier lesyndrome d'arthralgie femoro-patellaire de lachondromalacie de la rotule, oCu il y adegenerescence du cartilage articulaire de la rotule,et des autres sources de derangement interne, telleune maladie du menisque ou des lesionsosteochondrales. Un questionnaire attentifconcernant le mode de debut, les activitesdeclenchantes comme le fait de monter des escaliers,s'agenouiller et s'accroupir, permettra au medecind'identifier l'arthralgie femoro-patellaire. On doitaussi rechercher d'autres syndromes frequents desurutilisation et les diff6rencier des problemesattribuables a un vrai derangement interne.

Key words: Patellofemoral arthralgia, overusesyndromes, chondromalaca patella

Dr. Welsh is deputy chief of staff,and director of the sports medicineclinic, at the Orthopedic andArthritic Hospital, Toronto, and anassistant professor at the Universityof Toronto. Reprint requests to:Suite 319, 43 Wellesley St. East,Toronto, ON. M4Y lHl.

F ALL COMMON knee mala-Fdies, the patellofemoral derange-

ments are the most difficult to manage.Peripatellar and subpatellar pain isvery common, particularly in patientswho participate in running and jump-ing sports, yet overt pathology is sel-dom evident. The spectrum of normalanatomy and physiology is so widethat it is difficult to determine whichvariants predispose to pain and dys-function. Very often, the site and ori-gin of pain around the knee remainsobscure.Too often, this syndrome of knee-

cap pain has been called chondromala-cia patella. -This is erroneous, for

chondromalacia patella is a very spe-cific entity, whereby the articular car-tilage of the patella and occasionally ofthe opposing patellofemoral groovedegenerates. Fortunately, true chon-dromalacia patella is relatively rare,but crepitus and subpatellar pain areprobably the most common complaintsseen in a sports medicine clinic, wheremost knee problems will have someassociated patellofemoral dysfunction.

Patellofemoral ArthralgiaThe most common presenting symp-

tom is pain in or around the knee,associated with running, jumping,kicking, kneeling or crouching. Dis-comfort is commonly aggravated byascending and descending stairs; a sen-sation of instability or crepitus mayalso be noted. On examination, theonly positive findings may be tender-ness to palpation around or over thepatella and its tendons, or to compres-sion of the patella against the femoral

condyles. There are no signs of inter-nal derangement, there is no effusion,no lost range of motion or ligamentousinstability. There may be some mildquadriceps wasting and, occasionally,some retropatellar crepitus, but usuallythe examiner is unable to detect majorabnormality. This can lead the physi-cian to underestimate the significanceof the patient's complaints, or to er-roneously label the condition chondro-malacia. Both approaches do the pa-tient a gross disservice. A specificdiagnosis should be made in every in-stance.

EtiologicfactorsThe patella is a sesamoid bone lying

in the quadriceps apparatus, which en-hances the mechanical action of themuscles during extension. The patellais subject not only to the forcesdirected along the line of the quadri-ceps muscles and the infrapatellar ten-don, but also to the resultant vectors ofthese forces.

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An increase in quadriceps load re-sults in abnormal patellar pressures.The resulting pain is believed to be dueto stimulation of nerve endings in theunderlying subchondral bone but mayalso relate to strain in the retinacula orimpingement of the fat pad or the syn-ovium which are both richly endowedwith nerve elements.

Abnormal patellar pressuresInflexibility of the quadriceps mus-

cles is probably the most commoncause of primary, abnormal patellarpressures. During the adolescentgrowth spurt, bone growth may out-strip the rate at which muscle fibersstretch, causing abnormal muscletightness and excessive compressiveforces across the patella. As a result,patellofemoral arthralgia is common inteenagers.

Muscle injury, with hematoma andscar formation can cause similar ab-normal muscle tightness, as can surgi-cal intervention. Indeed, over-zealouscapsular closure after arthrotomy maysignificantly tighten the capsule,thereby increasing the patellofemoralpressures.

Abnormal patellar excursionThe line of the quadriceps' force is

basically along the shaft of the femur.The physiologic valgus of the knee de-fines a Q angle between the pull of themuscle and of the infrapatellar tendon.In the normal knee, the patella's natu-ral tendency to displace laterally is re-sisted by the medial stabilizing struc-tures, the distal fibers of the vastusmedialis and the medial retinaculum.Lateral excursion is further limited bythe prominent lateral femoral condyle.Genu valgum, excessive external tibialtorsion and pes planus effectively in-crease the Q angle and the lateral forceand may predispose to lateral subluxa-tion.

Failure of the medial structures(i.e., a lax retinaculum or weak quad-riceps, shortening or tightness of thelateral stabilizing structures, and bonyanomalies such as a flattened lateralfemoral condyle) also predispose toforce imbalance, resulting in lateraltilting or lateral excursion (subluxationor dislocation) of the patella. Minimalbut persistent recurrent subluxation ofthe patella is a major contributing fac-tor in the development of chondroma-lacia patella-but patellofemoral pres-sures and trauma are also important in

the pathogenesis of this condition.One feature common to all patients

with patellofemoral arthralgia is thatrepetitive activity has resulted in achronic overload or overuse syndrome;pain and diminished function are theconsequences. This syndrome resultsnot from trauma but from simple, ev-eryday use, as in sports. The repetitivenature of the activity, such as runningor jumping, exceeds the body's toler-ance to withstand what are scarcelymore than normal loads.

Clinical examinationClinical examination should deter-

mine precisely the pain's site of origin.Is the discomfort medially or laterallyrelated to the retinaculae? Is it relatedto the infrapatellar or subpatellar fatpad? Is it related to the synovial plicadown the medial side of the joint or inthe suprapatellar pouch? Effusion mayor may not be present, and examina-tion of the patella will determinewhether or not crepitus is present. Intrying to detect patella crepitus, do notbe confused by crepitus arising fromthe soft tissues of the fat pad and syn-ovium. True patellofemoral crepituswill be elicited when the knee is ex-tended against resistance from a flexedposition, and should be confirmedwith the knee in full extension, withthe patella pressed down and movedgently sideways, medially and la-terally. If crepitus is elicited in this po-sition, the patella itself is involved. Inmost cases of patellar arthralgia, thepatella itself will be undamaged.The rest of the standard knee exam-

ination should determine that there isno ligamentous instability or meniscalderangement. Note the leg's overallalignment, particularly any tendencyto genu valgum and any increase in thepatella's Q angle. The examination isnot complete until the feet have beenthoroughly examined for any tendencyto heel varus or valgus position. Avalgus heel will predispose to over-pronation of the forefoot, and mayproduce abnormal loading of the pa-tella, particularly with running.

Radiologic reviewPlain AP, lateral and tunnel views

give basic information about theknee's medial and lateral compart-ments. Skyline views of the patella arerequired in order to give an impressionof its relation to the lower end of thefemur. Views at 30° and 600 will show

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how the medial and lateral facets relateto the underlying femur, and give in-formation on the joint space and thethickness of articular cartilage. In truechondromalacia patella, where theremay be great crepitus and marked de-generation of the articular cartilage,often the cartilage space is not dimin-ished. Rather, there is almost hyper-trophy of the cartilaginous surface.

ManagementNearly all these syndromes will re-

spond to a conservative approach. Oc-casionally the aggravating activitymay be carried out at a reduced level,coupled when necessary with alteredtechnique and form. For example, achange from running to cycling maybe necessary, the emphasis being onmaintaining basic fitness until theprocess's natural history runs itscourse.

Although physiotherapy with short-wave diathermy and ultrasound oftenrelieves symptoms, intensive, individ-ual exercise therapy must be main-tained. Isometric quadricep setting andstraight leg raising, followed by pro-gressive, resisted exercises over thefinal five to ten degrees of knee exten-sion are emphasized. Resisted exer-cises through the full range of motionare to be avoided, because they applyexcessive compression across the pa-tella. Sequential faradism can be ap-plied if muscle bulk is significantly re-duced. Stretching must be equallyemphasized, in an effort to reduce theloads across the joint and at the sametime enhance the strength of the mus-cle group. Orthotics aimed at correct-ing pes planus and heel valgus mayhelp when the condition is contributingto abnormal patellar mechanics, par-ticularly in association with genu val-gum.The patient with patellofemoral

arthralgia not due to true degenerationor wear must be reassured that contin-uing the activity is safe and will notlead to degeneration, chondromalacia,or patellofemoral arthritis. Many ath-letes with a patellofemoral overloadsyndrome fear that continuing the ac-tivity will harm them. In many cases,it is only by working at a modifiedlevel of activity, gradually pushing thethreshold of tolerance upward, thatathletes can overcome the disqomfortsassociated with this syndrome. A run-ner may be forced to continue with a

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less demanding running program formany weeks before he can increase themileage, and then he will find that ashe strives for a new plateau, the syn-drome will recur. However, if the ex-aminer is convinced that there is nounderlying pathology, the athlete canpush on further with his sport. Thesesyndromes are particularly trouble-some not only to runners, but in mostracquet sports and in any jumpingsports such as basketball or volley-ball.

Chondromalacia PatellaFew patients who present with a pa-

tellofemoral overload syndrome, orpatellofemoral arthralgia, will actuallyhave true degenerative wear. These areindividuals with true chondromalaciapatella. The pathogenesis of chondro-malacia patella is poorly understood;abnormal patellofemoral excursionand patellofemoral pressure are two ofthe causative factors. Trauma may alsobe significant; there is no doubt that inthe young patient, there is often a his-tory of direct trauma to the front of theknee, from a fall or direct blow. Inthese patients, landing on the point ofthe patella causes it to impact againstthe femur, resulting in a direct contu-sion to the joint surface. This may wellbe the first stage in the breakdown ofthe cartilaginous surface, and may ac-count for many cases of true chondro-malacia patella.

Often, however, there is no historyof direct trauma to the knee, and hor-monal factors may well have played arole in the development of this condi-tion. During adolescence, and particu-larly during the growth spurt, the pa-tella's articular cartilage appears toproliferate, without the orderly regula-tion of growth that normally prevails.As a result, the ground substancebreaks down, and the collagenous fi-brils of the articular cartilage becomedisrupted, instead of forming normalarcades. The cartilage becomesfronded and looks almost like crab-meat, with deep crypts and clefts downto the chondral plate. With this breachin the integrity of the articular surface,the mechanical forces on the cartilagebecome deranged and further degen-eration occurs.

For the patient with chondromalaciapatella, patellar loading becomes veryuncomfortable indeed. Stairs and stepsare difficult, crouching and kneelinglikewise almost impossible and any of

the running sports where jarring andimpact loading occurs are impossible.Often there will be associated effusionand there's a coarse crepitus, whichcan be elicited on resisted loading ofthe knee when the leg is brought froma flexed to an extended position. Fur-thermore, in full extension any lateralmovement of the patella is associatedwith very definite crepitus, and asso-ciated pain. Very commonly, one ofthe most troublesome symptoms is re-current effusion in the knee. This maymake definitive treatment necessary.

Chondromalacia patella can truly bediagnosed only pathologically. Thisrequires clinical review of the knee bydirect visualization, and through a sur-gical specimen. Arthroscopy makesthis much easier, and also makes itpossible to debride some of the coarserareas. Often, this will be sufficient.

The conservative management ofchondromalacia patella follows thesame pattern as that for patellofemoralarthralgia. In addition, patients mayrequire nonsteroidal anti-inflammatorydrugs. Enteric-coated ASA should beused for adolescents, particularly ifthey are going through the growthspurt. During this phase, the cartilageis at its most hypertrophic. The ASAdefinitely eases pain and has an anti-inflammatory effect. It may also havea beneficial effect on the maturation ofthe articular cartilage, although this isunproven.

Fat Pad ImpingementOne of the most common forms of

patellofemoral arthralgia, readily con-fused with chondromalacia patella, isthe fat pad impingement syndrome.The significance of these very large,cushioning fat pads in the knee hasoften been overlooked. Lying deep tothe ligamentum patella, they becomepinched between the lower pole of thepatella and the opposing femur. Withrepetitive activity they may hyper-trophy, so that a tongue of tissue be-comes pinched between the patella andthe femur, leading to a painful over-load syndrome.

Acute impingement can occur withsudden forced extension of the knee.The fat pad is caught between the pa-tella tendon and the underlying fe-moral condyle. The mechanism of in-jury can be elicited from the history,and from noting pain and tenderness,medial and lateral to the patella tendonor within the joint.

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Chronic impingement syndromesoften develop without specific historyof trauma. With repetitive activity thefat pad becomes extremely sensitive,and examination will confirm distincttenderness on either side of the liga-mentum patella, and to patellar com-pression in the lower pole. Crepitus isoften elicited, but this is soft, andshould not be confused with crepitusof true chondromalacia patella. In myexperience, problems with the fat padoccur far more frequently than truechondromalacia patella.

With conservative treatments, fatpad syndromes will usually settle. Pa-tients with true chondromalacia cannotexercise, but those with fat pad over-load syndrome can certainly continueactivity without fear of harm. Even so,some patients become so sensitive thateven a steroid injection into the fat padfails to give relief, and surgical exci-sion becomes necessary.

Other Overuse SyndromesPatellofemoral arthralgias must be

differentiated from other very commonoveruse syndromes of the knee. Theseconditions are specific, defined enti-ties which must not be confused withtrue internal derangements, such asmeniscal pathology, ligamentous in-stability or osteochondral lesions ofthe joint surfaces.

Patellar tendonitisInflammation of the distal tendon of

the quadriceps muscle (suprapatellartendonitis), of the origin of the infra-patellar tendon (infrapatellar tendon-itis), and of the insertion of the infra-patellar tendon (Osgood-Schlatterdisease), are all overuse syndromes as-sociated with running and jumping.Pain and tenderness are usually lo-calized to the inflamed area, the dis-comfort tends to develop during thecourse of the activity and often persistsafterward.The initial treatments consist of

physiotherapy with local ice frictionsand ultrasound, and stretching exer-cises for the quadriceps. Oral non-steroidal anti-inflammatory medica-tions may be tried for ten to 15 days.As with all tendonitis, early aggressivetreatment is more successful than latertreatment when the condition ischronic.

Occasionally a steroid injection intothe tendon insertion may be needed,

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but be aware of tendon structures' pro-pensity to collagenous breakdown.Also, infrapatellar tendons have beenruptured by injection at this site.

Osgood-Schlatter diseaseThis is a localized tendonitis in ado-

lescents, occurring at the insertion ofthe ligamentum patella into the proxi-mal tibial epiphysis. Pressures on thesensitive growth area evoke a localdiscomfort which can be disabling.Ice, stretching exercises, and an infra-patellar strap may control pain andallow patients to continue sports.

Osgood-Schlatter disease tends tobe episodic and discomfort may some-times be so severe that activity must berestricted for weeks at a time. Mostadolescents pass through this conditionin two to three years, but sometimesthe symptoms persist until late adoles-cence or adulthood, with continuingproblems around the tibial tubercle in-sertion. A localized ossicle of ununitedepiphysis may be identified on plainX-rays, and excision required.

Prepatellar bursitisPrepatellar bursitis causes pain and

swelling in the bursal tissue over thepatella's anterior surface. The bursitisresults from either direct trauma or re-peated irritation. A fluctuating swell-ing can be aspirated, a local steroid in-jected and a compression dressingapplied. Follow-up care with an anti-inflammatory medication and therapywith ultrasound will settle most cases.In longstanding cases, surgical exci-sion of the bursa may be necessary.

Iliotibial band bursitisThis is a troublesome inflammation

of the bursa underlying the distal por-tion of the iliotibial tract on the lateralaspect of the knee. It results from thefriction of repetitive knee flexion andextension, associated with impactloading of the knee, as in jogging.This is a perplexing condition, becausethe athlete has no previous indicationof injury. It may strike suddenly, evenduring a race, with a sharp pain overthe lateral femoral condyle. It becomesso painful within 100 yards or so thatthe athlete is forced to discontinue theactivity. On walking, the knee seemsto improve spontaneously, but the painreturns when attempts are made to runagain.

This condition is so acute in onset

that it may be confused with internalderangement, but examination will re-veal the tenderness is over the lateralfemoral condyle, in the origin of thelateral ligament in the bursa, whichunderlies the iliotibial band.

With this condition a runner mustrecognize that he cannot run furtherthan the threshold of discomfortallows. When steady activity is main-tained over a reduced distance, even atan increased pace, the condition willoften disappear as mysteriously as itappeared. Ice friction treatments, ul-trasound, stretching and strengtheningexercises and oral anti-inflammatorymedication are often necessary to alle-viate the condition. Occasionally localsteroid injection into the bursa may beindicated. Rarely, a surgical releasebecomes necessary.

Pes anserine bursitisPes anserine bursitis is an inflamma-

tion of the bursa underlying the sar-torius, gracilis and semitendinosis ten-don complex on the medial aspect ofthe knee. This troublesome conditionaffects cyclists, runners and swimmersand is treated locally with ultrasoundand ice frictions. Oral anti-inflamma-tory medication and local steroids mayalso be helpful.

RetinaculitisInflammation of the medial and lat-

eral patella stabilizing structures pre-sents with pain and tenderness over theretinaculae, where they play over theunderlying femoral condyles, pinchingthe synovium and evoking pain from itdue to repetitive loading of the knee. Itis important to distinguish retinaculitisfrom true chondromalacia, for theprognosis is very different. Flexibilityexercises, particularly stretching outthe quadriceps, and patella mobilizingtherapy help relieve pressures over thefemoral condylar margins.

If the capsule of the knee is undulytightened following arthrotomy, therecan be marked increase in pressuresover the condylar margins, causingpain. Pain after surgery often stemsfrom overtightening the capsule; post-operative stretching exercises for thequadriceps are therefore an importantadjunct to any surgical intervention.

Surgical TreatmentsMost management of patellofemoral

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arthralgia syndromes and the otheroveruse syndromes around the kneemust remain conservative. However,there are occasions when symptomsbecome completely refractory tophysiotherapy and exercise. With truechondromalacia patella it may be nec-essary to arrest progressive degenera-tion. In managing chondromalacia pa-tella, arthroscopy can be used todebride and shave the back surface ofthe patella. At the same time, the lat-eral retinaculum is released to relievesome of the pressure on the patella'slateral facet.The longterm results of such inter-

vention remain in question; in somecases there is dramatic short-term re-lief, in others results may be disap-pointing. Open arthrotomy and articu-lar shaving has been advocated in thepast, but these procedures alone havenot been proven to have longterm ben-efit. However, when coupled with aprocedure to alleviate the pressures onthe patella (as in the elevation of the ti-bial tubercle insertion of the ligamen-tum patella), there can be a definitebenefit. A Maquet procedure wherebythe ligamentum patella insertion is ele-vated forward can definitely diminishpressures on the patella and signifi-cantly enhance results.The fat pad overload syndrome can

occasionally be so refractory thatdirect intervention is necessary.Arthroscopic excision of the fat padcan be attempted, but this structure isvery extensive, and extremely vascu-lar. I prefer to carry out a small arthro-tomy, excise the fat pad completelyand carefully cauterize the base to con-trol any bleeding.

Release of the ligamentum patella atits origin occasionally may be neces-sary in the athlete with a refractoryjumper's knee syndrome. Similarly,release of the iliotibial tract may benecessary in those with ongoing symp-toms from iliotibial friction syn-drome.

ConclusionThe common patellofemoral arthral-

gias must be clearly differentiatedfrom "true" pathologic processessuch as chondromalacia and other in-ternal derangements. These syn-dromes, though troublesome, canallow the athlete to continue an activesports program without fear of damag-ing the knee.

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