Đau gối trước: Chẩn đoán và điều trị pptx

Anterior Knee Pain: Diagnosis and Treatment Abstract Anterior knee pain is a frequent clinical problem. It provides a common challenge to diagnose and manage. Basic science studies have provided insight into the origin of anterior knee pain and refined understanding of the anatomy. Clinical evaluation has progressively focused on the contribution of the entire lower extremity to patellofemoral function. Nonsurgical management has been refined by the concept of the ″envelope of function″ and by increased understanding of the neuromuscular control of the knee. Indications for lateral release have been clarified and narrowed. Although anteromedial transfer of the tibial tuberosity is helpful in certain circumstances, reports of postoperative fracture have led to less aggressive rehabilitation protocols. Chondral resurfacing of the patellofemoral joint and patellofemoral arthroplasty are evolving. Emphasis should remain on nonsurgical management, which is sufficient in most patients. T he diagnosis and treatment of anterior knee pain is challeng- ing, and the topic has been well reviewed. 1-3 The term “anterior knee pain” is used to group together a number of different but related pathologic entities. The history and physical examination, complement- ed by imaging studies, are helpful in defining as precisely as possible the origin of the patient’s complaint. Pa- tellofemoral symptoms fall into two general categories: instability and pain. Overlap of pain and instability does occur, but most often, symp- toms are more directly caused by one or the other. The patient with true patellar in- stability reports that the patella ei- ther dislocated (requiring a reduc- tion) or shifted laterally (partial dislocation with spontaneous reduc- tion). Such injuries are typically as- sociated with weight bearing and torsional trauma. It is important not to confuse patellar instability with reports of the knee “giving way” or buckling. Such symptoms typically include the knee collapsing into flexion and are more likely caused by quadriceps insufficiency second- ary to pain, deconditioning, or sec- ondary joint effusion. True patellar instability is a topic separate from the subject of anterior knee pain. The origin of anterior knee pain may be patellofemoral when it oc- curs during prolonged knee flexion or when climbing or descending stairs. The pain is often localized in the peripatellar or retropatellar area and may be vague in nature. Careful attention to pain diagrams can be helpful in localizing symptoms and in focusing the physical examina- tion. 4 Determining whether the pain is constant, activity related, or sharp and intermittent can help narrow the list of potential diagnoses. Table 1 provides an overview of potential William R. Post, MD Dr. Post is in private practice, Mountaineer Orthopedic Specialists, LLC, Morgantown, WV. Neither Dr. Post nor the department with which he is affiliated has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article. Reprint requests: Dr. Post, Mountaineer Orthopedic Specialists, LLC, 1197 Pineview Drive, Morgantown, WV 26505. J Am Acad Orthop Surg 2005;13:534- 543 Copyright 2005 by the American Academy of Orthopaedic Surgeons. 534 Journal of the American Academy of Orthopaedic Surgeons Table 1 Overview of Diagnosis and Treatment of Anterior Knee Pain Type of Anterior Knee Pain Possible Diagnosis Key Elements of History and Physical Examination Testing Management Constant pain, not activity- related Sympathetic mediated pain Evaluate for signs and symptoms of sympathetic dysfunction Bone scan Pain management referral for sympathetic blockade Postoperative neuroma Focal tenderness reproducing symptoms, especially over scars Local anesthetic injection Neuroma excision Referred radicular pain Examine hip, lumbar spine, and saphenous nerve Radiographs, MRI, bone scan Determined by primary pathology Symptom magnification for secondary gain Careful attention to psychosocial issues Psychiatric evaluation Psychiatric counseling Sharp intermittent pain Loose bodies; unstable chondral pathology Effusion likely with loose body; differentiate from true patellar instability by history and by examining for patellofemoral ligament laxity Radiographs, MRI, arthroscopy Arthroscopy, chondroplasty Activity-related pain Soft-tissue overload without patellar malalignment (eg, patellar tendinitis, quadriceps tendinitis, pathologic plica syndrome, fat pad syndrome, ITB syndrome, early lateral patellar compression syndrome) Focal tenderness over the involved structure reproducing the symptom; associated flexibility deficits (eg, prone quadriceps testing, ITB syndrome, lateral retinaculum, hamstring, hip) MRI (soft-tissue assessment); CT scan when malalignment suspected Rehabilitation, arthroscopic or open treatment for tendinosis or other specified pathology, lateral release with documented patellar tilt without instability and minimal chondrosis Articular tissue overload (eg, posttraumatic chondromalacia or arthrosis, degenerative arthrosis from chronic malalignment) Effusion; asymmetric crepitus with passive flexion/extension; pain with direct articular compression in various degrees of flexion Radiographic assessment: patellar axial; MRI, CT with or without arthrogram; injections, bone scan Rehabilitation, realignment with chondroplasty or resurfacing procedures to unload pathologic lesions, arthroplasty in end-stage conditions in patients with limited activity level Inflammatory arthritides, myalgias Examine other joints and typical systemic symptoms to confirm Serologic testing Pharmacologic agents Systemic disease or illness producing weakness and general deconditioning History of such illness or inactivity, nonspecific examination findings Rehabilitation and medical treatment for the specific medical condition (eg, thyroid hormone for hypothyroidism) CT = computed tomography, ITB = iliotibial band, MRI = magnetic resonance imaging William R. Post, MD Volume 13, Number 8, December 2005 535 diagnoses that can cause anterior knee pain as well as suggestions for physical examination, further test- ing, and management. Accurate di- agnosis is key to focusing both surgi- cal and nonsurgical management. Anatomy and Pathomechanics Trying to unravel the mysteries of anterior knee pain begins with im- proved understanding of the anato- my. Biedert et al 5 found that free nerve endings are concentrated in the patellar tendon, retinacular tis- sues, pes anserinus, and, in particu- lar, the synovial tissues and fat pad. The pain sensitivity of intra- articular structures was defined by Dye, who described the sensations he experienced during arthroscopic probing of his own knees without intra-articular anesthesia. 6 He found that the fat pad and synovial tissues were especially sensitive and that the articular surfaces, menisci, and ligaments were much less sensi- tive. 6 Articular cartilage is aneural, but subchondral bone has the poten- tial to generate pain when overload- ed by serious overlying cartilage de- ficiency. Other studies have supported a soft-tissue origin of the pain. Sub- stance P and calcitonin gene–related peptide, which are neurotransmit- ters of nociceptive fibers, are prom- inent in retinacular tissues and in the fat pad. Sanchis-Alfonso et al 7 found perivascular proliferation of nociceptive axons in the retinacular tissue of patients with anterior knee pain at the time of realignment sur- gery. Neural growth factor hastens neural proliferation and can be in- duced by ischemia. 8 Higher levels of neural growth factor also have been found in the lateral retinaculum of patients with pain as a primary com- plaint compared with the levels found in patients with patellofemo- ral instability. These observations have led to the hypothesis that is- chemia of the retinacular tissues (perhaps caused by tension overload) may induce pathologic neural prolif- eration and pain. 9 This is one poten- tial mechanism for the occurrence of anterior knee pain provoked by pa- tellar knee flexion. Witonski and Wagrowska- Danielewicz 10 reported that sub- stance P–immunoreactive nerve fi- bers are widespread within the soft tissues around the knee. These tis- sues include the retinaculum, syn- ovium, fat pad, and, in some circum- stances, bone. In patients with anterior knee pain, more nociceptors were found in the fat pad and medi- al retinaculum than in patients with osteoarthritis or anterior cruciate ligament injury. In addition to veri- fying the presence of a rich nerve supply to these soft tissues, these studies support the concept of chronic nerve injur y in the soft tis- sues as a source of anterior knee pain. Subchondral bone is also richly innervated. Several studies have shown elevated intra-articular pres- sure in the patella to be associated with anterior knee pain. Decompres- sion has been tried when pain was provoked by a pain provocation test, which was believed to increase intraosseous pressure. Preliminary success has been reported, even though the provocation test did not produce pain in all patients with an- terior knee pain. 11,12 Understanding and analysis of pa- tellar tracking has progressed mark- edly, as demonstrated by Katchburi- an et al. 13 Consistent terminology for patella position and patellar tracking are both improving; appre- ciation of the complexity of the mo- tion involved is a necessity (Figure 1). Motions that can be measured in- clude medial and lateral translation of the patella, axial plane rotation of the patella (ie, tilt), coronal plane ro- tation (ie, patellar spin), and sagittal plane flexion. 3 In vivo and in vitro studies show that in early flexion, the patella shifts medially 4 to 9 mm as it is drawn into the trochlea. The patellae generally tilt medially in vitro during early flexion by <4° be- fore beginning to tilt laterally up to <4° as flexion progresses to 90°. In vivo studies of patellar tilt have been less consistent. Studies of coronal plane patellar rotation also are not very consistent, but they generally demonstrate that the inferior pole of the patella rotates laterally as knee flexion progresses. There is much room for improvement in the clini- cal evaluation of patellar motion. As yet, in vivo understanding of patellar tracking is incomplete. Dye et al 14 investigated the soft tissues anterior to the patella and found differences compared with tra- ditional anatomic texts. Apparently, a superficial transverse fascial layer exists, with a deeper intermediate oblique aponeurotic layer, both of which are superficial to the deep rec- tus femoris fibers, which are directly applied to the bone of the patella. Eckhoff et al 15 reported that the sul- cus of the trochlea in both normal and osteoarthritic knees is actually slightly lateral to the midplane be- tween the medial and lateral femoral condyles. Their finding is contrary to the traditional assumption that the sulcus is in the midline. Radio- graphic imaging of the patella dem- onstrated that the geometric center of the patella was slightly lateral (2.2 ± 0.9 mm) to the patellar ridge. 16 Yet when interpreting imaging studies of the patellofemoral joint, bony con- gruence often may not reflect the real articular congruence. Stäubli and colleagues 17,18 used magnetic res- onance arthrograms to demonstrate that, because of variable thickness of the articular cartilage on the patella, images of bone that appear incongru- ent may actually have excellent car- tilage congruity. Clinical Evaluation It is important to remember that not all anterior knee pain is associated with measurable abnormalities of patellar alignment or individual an- Anterior Knee Pain 536 Journal of the American Academy of Orthopaedic Surgeons atomic variations. Patellofemoral malalignment must not be consid- ered a synonym for anterior knee pain. Measurable malalignment of the patellofemoral joint may or may not be a key factor in any specific patient with anterior knee pain. Studies have failed to be sensitive in consistently finding radiographic malalignment in patients with patel- lofemoral pain. 19 Are radiographic findings (eg, shallow sulcus, patella alta, lateral tilt angle) pathologic if the patient is asymptomatic? Or is the effect of the preexisting differ- ence in morphology critical only in the presence of injury, repetitive overload, or neuromuscular decom- pensation? There are no definite an- swers to these questions. Misunderstanding of the patho- genesis and inappropriate treatment can occur when all pain is assumed to be associated with some degree of patellar malalignment. This as- sumption may result in surgical re- alignment in patients in whom alignment may not be the primary problem. A well-intentioned opera- tion to realign a normally aligned pa- tellofemoral joint can lead to a poor outcome. Imbalances in the extensor mechanism include dynamic and static neuromuscular factors. The patellar position on static imaging is only part of the pathophysiology . Re- cent literature has pointed out the value of recognizing other causes of patellofemoral pain in patients with normal anatomic alignment, such as patellar or quadriceps tendinitis, 20 postoperative neuromas, 21 and sa- phenous neuritis. 22 The role of the entire leg in the pathogenesis of anterior knee pain has come under increased scrutiny. Witvrouw et al 23 evaluated 282 ado- lescents (average age, 18.6 years) and noted that 7% to 10% developed pa- tellofemoral pain within 2 years. An- thropometric, physical examination, psychological, and electromyograph- ic data were collected prospectively to discern which factors would pre- dict the onset of pain. Notable find- ings were decreased quadriceps and gastrocnemius flexibility, increased vastus medialis obliquus (VMO) re- flex response time and delayed VMO firing versus the vastus lateralis, de- creased explosive strength, and in- creased thumb to forearm mobility. Factors that did not correlate with the onset of knee pain included alignment (ie, Q angle), psychologi- cal testing, isokinetic strength, and any of the anthropometric data (eg, height, weight). Two important studies found electromyographic dif- ferences, proving that contraction of the vastus lateralis came before the VMO in symptomatic patients com- pared with control subjects. 24,25 The hip extensor muscles play a critical role in lower extremity func- tion. Zhang et al 26 found that the hip extensors contribute 25% of the energy absorption during landing. When the hip musculature does not absorb its share of the load, other parts of the extremity must compen- Figure 1 Clinically relevant patellar position relative to the trochlea. A, Axial view demonstrating medial and lateral translation and patellar rotation (commonly called tilt). B, Coronal view demonstrating internal and external rotation (commonly called spin). C, Sagittal view demonstrating flexion. (Adapted with permission from Post WR, Teitge R, Amis A: Patellofemoral malalignment: Looking beyond the viewbox. Clin Sports Med 2002;21:521-546.) William R. Post, MD Volume 13, Number 8, December 2005 537 sate. Deficits in hip strength add to load on the knee, even independent of the rotational changes that may occur in the presence of hip weak- ness. Providing further evidence of entire extremity involvement, Baker et al 27 tested 20 patients with anteri- or knee pain and found that knee joint proprioception was abnormal in both weight-bearing and non– weight-bearing tests compared with a control population. Understanding patellofemoral disorders does require more than a thorough understanding of anatomy. Dye 28 defines the envelope of func- tion as the “range of load that can be applied across an individual joint in a given period without supraphysio- logic overload or structural failure.” Essentially, an asymptomatic joint has adequate tissue homeostasis, so the amount of load applied to the in- volved joint is successfully handled. When the joint is out of homeosta- sis, pain results. The ability of a j oint to tolerate loading depends on mul- tiple factors, not just the radiograph- ic alignment of the joint. The abso- lute amount of loading over time is an important factor in overuse inju- ries. For example, patients suffering from anterior knee pain caused by blunt trauma may have a positive bone scan (a measure of physiology, not structure) that resolves over time as their pain does. 29 The knee is out of homeostasis on the bone scan while it is abnormal, but homeosta- sis is restored over time. Keeping pa- tients within their pain-free enve- lope of function, however narrow that may be, is a key to successful treatment. For example, a previously asymp- tomatic middle-aged, decondition- ed, sedentary, slightly overweight woman who rapidly increases her activity by taking a five-mile hike up a mountain trail may present 10 days later with anterior knee pain, a small effusion, peripatellar tender- ness, and a patellar axial radiograph suggesting mild patellofemoral ar- throsis with lateral patellar tilt, and lateral subluxation. Her increased activity resulted in loss of joint tis- sue homeostasis. Relative rest, pain control, and anti-inflammatory mo- dalities likely would restore her daily function, even in the presence of her preexisting radiographic “malalignment.” Acute treatment consists of keeping her within her new envelope of function (ie, activi- ties with low enough load that she is minimally symptomatic), while working gradually to increase her envelope of function by weight loss, strengthening, and flexibility exer- cises. If such a patient does not seek care but rather waits out the pain, she would likely become weaker from the decreased activity level and less flexible from the decrease in activity; also, she might gain weight because of the inactivity. Similarly, patients with systemic illnesses, such as thyroid disorders or cancer, can develop knee pain as their muscle weakness decreases their envelope of function. The next time such a patient tries to increase her or his activity level, the envelope of function is even smaller. The pa- tient becomes caught in this cycle and presents much later with a his- tory of chronic knee pain and radio- graphic evidence of malalignment. Rescue from the deconditioned state is not possible in some patients, and surgery may be necessary. Theoreti- cally, a patient who does not respond to a rehabilitation program has in- curred such a degree of macrostruc- tural damage that the joint cannot return to a homeostatic state. Thus, surgical intervention to remove the ongoing focus of inflammation or to realign the patellofemoral joint to decrease pathologic loading would be rational. It is important to remember that there are no absolute radio- graphic indications for surgery. Malalignment can be understood as a situation “where bony align- ment, joint geometry, soft tissue re- straints, neuromuscular control and functional demands combine to pro- duce symptoms as a result of abnor- mally directed loads which exceed the physiological threshold of the tissues.” 3 With regard to surger y for realignment, current clinical stan- dards for assessing patellofemoral alignment lack complete informa- tion, such as patellar spin and sagit- tal plane flexion. Understanding of the effect of standard realignment procedures on all components of alignment and tracking is currently limited. 30 Unfortunately, in vivo understanding of the effect of re- alignment procedures on three- dimensional tracking is even more lacking. With increased appreciation of the pathophysiology of soft-tissue pain comes the consideration that symptomatic relief may occur as a result of cutting certain soft-tissue structures, in addition to (or possibly independent of) any effect that sur- gery may have on macrostructural alignment. Even the postoperative period of relative rest and structured rehabilitation may contribute to res- toration of joint homeostasis. Nonsurgical Management Although controversy exists over the best methods to improve leg strength in patients with anterior knee pain, the traditional concept of trying to achieve isolated VMO exercise is not supported by extensive and persua- sive recent literature. 31 One random- ized study evaluated the effects of open kinetic chain exercise (non– weight-bearing) versus closed chain exercise (weight-bearing) in a group of patients with anterior knee pain. 32 Although both types of exercise pro- duced improvements in strength, pain relief, and return to function, the closed chain exercises produced less pain, better triple jump (func- tional improvement), and less sub- jective “clicking.” It would be short- sighted to discard either open or closed chain exercises entirely. Several thorough reviews of non- surgical treatment have been pub- lished recently; 33,34 many are partic- Anterior Knee Pain 538 Journal of the American Academy of Orthopaedic Surgeons ularly notable. Doucette and Goble 35 reported that 84% of pa- tients improved after 8 weeks of quadriceps rehabilitation and stretching. Patellar axial radiographs demonstrated some improvement after treatment, although the values were within previously published normal limits at both times, and val- ues were equivalent between the symptomatic and asymptomatic knees. Long-term (7-year) follow-up of 49 patients treated with quadri- ceps exercises, rest, and nonsteroidal anti-inflammatory drugs showed that nearly 75% of patients main- tained improvement from 6 months to 7 years. 36 Many factors were stud- ied, including radiographs, magnetic resonance imaging, and other base- line clinical findings, but none corre- lated with the treatment result. 37 Unfortunately, no criteria, examina- tion, or treatment predicted which patients would respond well. In par- ticular, patellar taping has generated much interest, with studies showing pain relief, alterations in the timing of VMO contraction, and increased exercise tolerance. 38,39 Although all of these studies con- firmed that nonsurgical manage- ment can be successful and shed light on the nature of the problem, only very recently has a double-blind multicenter placebo-controlled trial of nonsurgical treatment been re- ported. Seventy-one subjects aged <40 years were randomly assigned to either a placebo or a treatment group. 40 Subjects were included if they reported anterior or retropatel- lar knee pain on at least two of the following activities: prolonged sit- ting, stairs, squatting, running, kneeling, and hopping/jumping. Pa- tients had symptoms for at least 1 month, an average pain level of 3 on a 0 to 10 visual analog pain scale, and insidious onset of symptoms. The treatment group had six weekly visits involving patellar taping, quadriceps training with biofeed- back, gluteal strengthening, and an- terior hip and hamstring stretching. The placebo group had placebo tap- ing, turned-off ultrasound, and a pla- cebo “medicated gel.” Thirty-five percent of patients in the placebo group believed they were in the ac- tive treatment group. When mea- sured by improvement in pain or function, the treatment group showed statistically (P ≤ 0.04) better improvements compared with the placebo group (which also showed some improvement). Therefore, a nonsurgical program must include activity modification based on patient history. Athletes must modify their training, and ad- justments should be made in work and daily activities for nonathletes. Such modifications are important to get the patient back within his or her envelope of function. Particular at- tention also should be paid to flexi- bility, especially of the quadriceps, a common deficit in patients with an- terior knee pain. Strengthening must be done without causing severe pain. Strengthening may often be facilitat- ed by patellar taping. Open or closed chain exercise programs are individ- ualized to limit pain, which will fa- cilitate regular exercise and effective strengthening. Emphasis on hip strengthening has also been very helpful. Nonsurgical management should be pursued until both the cli- nician and patient are certain that a plateau has been reached in the lev- el of pain and function. This usually requires at least 3 months of careful and compliant rehabilitation. Be- cause very few patients with anteri- or knee pain do not respond to reha- bilitation, providers would be well advised to carefully reconsider the differential diagnosis when faced with a patient who has not respond- ed as expected. Surgical Management Because of the success of nonsurgi- cal management, surgery for anteri- or knee pain is not necessary in most patients. Successful surgical treat- ment requires an accurate diagnosis, taking particular care to ascertain whether there are symptoms of pa- tellar instability or signs of patel- lofemoral malalignment on physical examination and imaging studies. Patients with normal alignment and no instability may be symptomatic from tendinosis in the quadriceps or patellar tendons, pathologic hyper- trophy and inflammation in the me- dial plica, or less common causes (eg, neuromas). Severe damage to the articular surface of the patella or the trochlea can at times be the isolated cause of symptoms. However, before concluding that the anterior knee pain is caused by chondromalacia of the patella, other causes must be ruled out. Isolated le- sions of the articular cartilage of the patellofemoral joint are one of the less common causes of anterior knee pain. In such patients, arthroscopic débridement of Outerbridge grade 2 and 3 chondral lesions can be useful. In their review of 36 patients with chondromalacia patellae, Federico and Reider 41 reported 57.9% good or excellent results in patients with traumatic onset; patients with atrau- matic onset had 41.1% good or ex- cellent results. All but four patients thought the surgery was beneficial. In one recent randomized, non- blinded study of a similar group of patients with Outerbridge grade 2 and 3 chondromalacia, bipolar radio- frequency débridement was com- pared with mechanical débridement alone. 42 Both groups improved at fi- nal 2-year evaluation, but the radio- frequency group scored significantly better (P = 0.0006). However, con- cerns remain about the potentially damaging long-term effects of radio- frequency energy on bone and carti- lage. 43 Although confirmation of the role of radiofrequency chondroplasty will depend on future randomized, blinded studies, these studies 41,42 to- gether show the positive value of chondroplasty in carefully selected patients with grade 2 and 3 lesions. Lateral release can be effective in treating a well-defined subset of pa- William R. Post, MD Volume 13, Number 8, December 2005 539 tients with anterior knee pain, but it is seldom needed. Most patients with pain and a tight lateral retinac- ulum can be effectively treated non- surgically. Lateral release may help by relieving pressure in the lateral retinaculum, dividing neuromatous nerves in the lateral retinaculum, or relieving pressure on the lateral fac- et of the patella; at present, the exact mechanism cannot be stated with certainty. The role of lateral release in managing anterior knee pain has been clarified in the past 10 years. Several studies have shown that the ideal candidate is a patient with no history of patellar instability. 44,45 The degree of chondral damage also seems to be important. Aderinto and Cobb 46 reported satisfactory results in only 59% of patients with ad- vanced patellar arthrosis treated with lateral release. Conversely, Shea and Fulkerson 47 reported 92% good and excellent results after later- al release when there were no chon- dral lesions greater than grade 1 and 2 and there was evidence of lateral tilt on computed tomography. O’Neill 48 compared the results of arthroscopic lateral release with those of open lateral retinacular lengthening and found slightly bet- ter results after the lengthening pro- cedure, although chondral damage was less severe in this group. This study raises the question whether a lengthening procedure is a good al- ternative to release. The biomechan- ical effects of lateral release have been shown to be related to the length of the release, especially in the distal direction. Although it is not known with certainty the clini- cally necessary amount of release, extending the release distally to the level of the tibiofemoral joint line does result in a measurable increase in patellar mobility. 49 Inarecentsur- vey of the International Patellofem- oral Study Group (a group of clini- cians with special interest and expertise in patellofemoral disor- ders), lateral release was an infre- quently done procedure. Indications for the procedure were anterior knee pain with evidence of a tight lateral retinaculum on physical examina- tion. 50 Complications of lateral release can include persistent or worsening pain or instability. When present, these complications can make the preoperative symptoms seem minor. Particularly in the setting of a nor- mally aligned patella that has been treated with lateral release, medial subluxation can occur. In this situa- tion, an excessive lateral release that included division of the vastus later- alis tendon also should be suspect- ed. Medial subluxation must be suspected clinically in any patient reporting persistent pain after later- al release. 51 Symptoms often include a sense of the patella moving lateral- ly, a complaint that can mislead cli- nicians. The cause of this sensation is the patella’s momentarily sublux- ating medially out of the trochlea in early flexion, then snapping back lat- erally into the trochlea with further flexion. When the clinician fails to recognize this diagnosis and instead interprets the symptoms to be recur- rent lateral subluxation, further pro- cedures, such as tibial tuberosity medial transfer or medial reefing, may be recommended. However, such procedures would only worsen the symptoms. Medial patellar subluxation must be confir med by clinical examina- tion. Two maneuvers have been de- scribed. Fulkerson 52 recommended pushing the patella medially with the knee in extension, then suddenly flexing the knee. When this repro- duces the complaint, medial sublux- ation is likely. Nonweiler and DeLee 53 suggested examining the in- volved knee in a lateral position. The involved knee is placed with the lat- eral side up, allowing the involved patella to sag via gravity medially out of the trochlea. The patient with medial patellar subluxation will be unable to flex the knee. Nonsurgical management can help to confirm this diagnosis if taping or bracing the patella into a more lateral position decreases symptoms. Hughston et al 54 found that 68% of patients re- ported improvement in their func- tional levels and 75% reported sub- jective improvement by attempts at repair or reconstruction of the lateral retinaculum. Surgical management of this condition involves repair or reconstruction of the lateral release defect; although helpful, this is best considered as a salvage procedure. Patients with radiographic or ar- throscopic evidence of lateral patel- lar tilt and subluxation who have failed persistent and patient nonsur- gical management can improve sig- nificantly after lateral release and anteromedial tibial tuberosity trans- fer. Pidoriano et al 55 correlated the results of anteromedial tibial tuber- cle transfer with the location of car- tilage lesions on the patella; they found that proximal and global pa- tellar lesions did less well. Their findings correlate with laboratory studies showing that anterior tuber- osity transfer, while decreasing over- all load, shifts load disproportionate- ly to the proximal patella. Careful consideration of the location of car- tilage lesions is recommended when contemplating tuberosity transfer, just as one would do with any other osteotomy to avoid transferring load onto articular lesions. Early weight bearing after antero- medial tubercle transfer should be avoided; two series have demon- strated the potential for fracture dur- ing full weight-bearing activities be- tween 4 and 7 weeks. 56,57 Based on this information, rehabilitation should include only partial weight bearing until osteotomy healing is complete, both radiographically and clinically. One report indicated that two athletes sustained tibial frac- tures while jogging 6 months postop- eratively; this finding is extremely uncommon, however. 58 Procedures to restore cartilage in- tegrity to the patellofemoral joint have not met with widespread suc- cess. Efforts are ongoing to evaluate Anterior Knee Pain 540 Journal of the American Academy of Orthopaedic Surgeons the usefulness of autologous chon- drocyte implantation and osteo- chondral transfers. Only relatively small numbers of cartilage-restoring procedures in the patellofemoral joint have been reported, and overall results are mixed. Experience has shown that careful evaluation and correction of patellofemoral align- ment must be included. 59-62 Less ag- gressive procedures, such as chon- droplasty, microfracture, or abrasion, may be equally advantageous and should be considered first-line treat- ments. 63 Patellofemoral arthroplasty can be considered in the presence of true end-stage arthrosis. 64-66 Resurfacing of the patellofemoral joint should be done only in low-demand patients after very careful clinical evaluation clearly shows that this articulation is the sole cause of symptoms. A bone scan may be a helpful adjunc- tive test in this setting; significant uptake in the tibiofemoral joint indi- cates that isolated patellofemoral ar- throplasty is not appropriate. Mont et al 67 suggested total knee arthro- plasty for patients aged >55 years with primarily patellofemoral arthri- tis. Special care is needed at the time of surgery to ensure that the exten- sor mechanism is well aligned. Sur- geons undertaking patellofemoral replacement should be very experi- enced in patellofemoral realignment procedures and should be prepared to combine them with arthroplasty as needed. Summary Despite the prevalence of anterior knee pain, much is unknown regard- ing the etiology, pathomechanics, and management of the many caus- es of this symptom. To label this set of disorders as “patellofemoral syn- drome” is worrisome because it may deter some clinicians from trying to reach a more precise diagnosis. Cli- nicians should strive for the greatest possible degree of diagnostic accura- cy and specificity to maximize out- comes. A greater understanding of the natural history of different causes of anterior knee pain also would be of great value; learning to predict which lesions progress over time would allow the clinician to treat those lesions more aggressively. Hypotheses regarding potentially is- chemic neurologic changes that may result from excessive soft-tissue ten- sion may produce insight into new treatments. Although significant in- sights have been made in the past 10 years regarding the understanding of the pathophysiology, diagnosis, and treatment of anterior knee pain, there is room for improvement in all areas. Particularly promising devel- opments include dynamic magnetic resonance imaging and advances in nonsurgical management in treating the entire extremity, with particular emphasis on the key role of the hip muscles in controlling femoral posi- tion. Improvements in imaging ar- ticular cartilage may make possible more precise diagnosis of the loca- tion and severity of cartilage lesions; however, clinicians need to be cau- tious in concluding that the articular cartilage lesion is the cause of symp- toms. Clinicians still need to im- prove their understanding of the role and boundaries of surgery in anteri- or knee pain. Currently, nonsurgical management remains the most pre- dictable method of treatment. References Evidence-based Medicine: Referenc- es 23, 32, 36, 37, 40, 48, and 63 are level I or II evidence-based studies. 1. Fulkerson JP: Patellofemoral pain dis- orders: Evaluation and management. J Am Acad Orthop Surg 1994;2:124- 132. 2. Post WR: Clinical evaluation of pa- tients with patellofemoral disorders. Arthroscopy 1999;15:841-851. 3. Post WR, Teitge R, Amis A: Patel- lofemoral malalignment: Looking be- yond the viewbox. Clin Sports Med 2002;21:521-546. 4. Post WR, Fulkerson J: Knee pain dia- grams: Correlation with physical ex- amination findings in patients with anterior knee pain. Arthroscopy 1994;10:618-623. 5. Biedert RM, Stauffer E, Friederich NF: Occurrence of free nerve endings in the soft tissue of the knee joint: A his- tologic investigation. Am J Sports Med 1992;20:430-433. 6. Dye SF, Vaupel GL, Dye CC: Con- scious neurosensory mapping of the internal structures of the human knee without intraarticular anesthesia. Am J Sports Med 1998;26:773-777. 7. Sanchis-Alfonso V, Rosello-Sastre E, Monteagudo-Castro C, Esquerdo J: Quantitative analysis of nerve chang- es in the lateral retinaculum in pa- tients with isolated symptomatic patellofemoral malalignment: A pre- liminary study. Am J Sports Med 1998;26:703-709. 8. Biedert RM, Sanchis-Alfonso V: Sources of anterior knee pain. Clin Sports Med 2002;21:335-347. 9. Sanchis-Alfonso V, Rosello-Sastre E, Revert F: Neuralgrowth factor expres- sion in the lateral retinaculum in painful patellofemoral malalignment. Acta Orthop Scand 2001;72:146-149. 10. Witonski D, Wagrowska-Danielewicz M: Distribution of substance-P nerve fibers in the knee joint in patients with anterior knee pain syndrome: A preliminary report. Knee Surg Sports Traumatol Arthrosc 1999;7:177-183. 11. Miltner O, Siebert CH, Schneider U, Niethard FU, Graf J: Patellar hyper- tension syndrome in adolescence: A three-year follow up. Arch Orthop Trauma Surg 2003;123:455-459. 12. Schneider U, Breusch SJ, Thomsen M, Wenz W, Graf J, Niethard FU: A new concept in the treatment of anterior knee pain: Patellar hypertension syn- drome. Orthopedics 2000;23:581- 586. 13. Katchburian MV, Bull AM, Shih YF, Heatley FW, Amis AA: Measurement of patellar tracking: Assessment and analysis of the literature. Clin Orthop 2003;412:241-259. 14. Dye SF, Campagna-Pinto D, Dye CC, Shifflett S, Eiman T: Soft-tissue anat- omy anterior to the human patella. J Bone Joint Surg Am 2003;85:1012- 1017. 15. Eckhoff DG, Montgomery WK, Stamm ER, Kilcoyne RF: Location of the femoral sulcus in the osteoarthrit- ic knee. J Arthroplasty 1996;11:163- 165. 16. Asano T, Akagi M, Koike K, Nakamu- ra T: In vivo three-dimensional patel- William R. Post, MD Volume 13, Number 8, December 2005 541 lar tracking on the femur. Clin Orthop 2003;413:222-232. 17. Staeubli HU, Bosshard C, Porcellini P, Rauschning W: Magnetic resonance imaging for articular cartilage: Cartilage-bone mismatch. Clin Sports Med 2002;21:417-433. 18. Stäubli HU, Dürrenmatt U, Porcellini B, Rauschning W: Anatomy and sur- face geometry of the patellofemoral joint in the axial plane. J Bone Joint Surg Br 1999;81:452-458. 19. Laprade J, Culham E: Radiographic measures in subjects who are asymp- tomatic and subjects with patellofem- oral pain syndrome. Clin Orthop 2003;414:172-182. 20. Popp JE, Yu JS, Kaeding CC: Recalci- trant patellar tendinitis: Magnetic resonance imaging, histologic evalua- tion, and surgical treatment. Am J Sports Med 1997;25:218-222. 21. Kasim N, Fulkerson JP: Resection of clinically localized segments of pain- ful retinaculum in the treatment of selected patients with anterior knee pain. Am J Sports Med 2000;28:811- 814. 22. Morganti CM, McFarland EG, Cosgar- ea AJ: Saphenous neuritis: A poorly understood cause of medial knee pain. J Am Acad Orthop Surg 2002;10:130- 137. 23. Witvrouw E, Lysens R, Bellemans J, Cambier D, Vanderstraeten G: Intrin- sic risk factors for the development of anterior knee pain in an athletic pop- ulation: A two-year prospective study. Am J Sports Med 2000;28:480-489. 24. Cowan SM, Bennell KL, Hodges PW, Crossley KM, McConnell J: Delayed onset of electromyographic activity of vastus medialis obliquus relative to vastus lateralis in subjects with patel- lofemoral pain syndrome. Arch Phys Med Rehabil 2001;82:183-189. 25. Owings TM, Grabiner MD: Motor control of the vastus medialis oblique and vastus lateralis muscles is dis- rupted during eccentric contractions in subjects with patellofemoral pain. Am J Sports Med 2002;30:483-487. 26. Zhang SN,Bates BT, Dufek JS: Contri- butions of lower extremity joints to energy dissipation during landings. Med Sci Sports Exerc 2000;32:812- 819. 27. Baker V, Bennell K, Stillman B, Cow- an S, Crossley K: Abnormal knee joint position sense in individuals with pa- tellofemoral pain syndrome. J Orthop Res 2002;20:208-214. 28. Dye SF: The knee as a biologic trans- mission with an envelope of function: A theory. Clin Orthop 1996;325:10- 18. 29. Dye SF, Boll DA: Radionuclide imag- ing of the patellofemoral joint in young adults with anterior knee pain. Orthop Clin North Am 1986;17:249- 262. 30. Mizuno Y, Kumagai M, Mattessich SM, et al: Q-angle influences tib- iofemoral and patellofemoral kine- matics. J Orthop Res 2001;19:834- 840. 31. Malone T, Davies G, Walsh WM: Muscular control of the patella. Clin Sports Med 2002;21:349-362. 32. Witvrouw E, Lysens R, Bellemans J, Peers K, Vanderstraeten G: Open ver- sus closed kinetic chain exercises for patellofemoral pain: A prospective, randomized study. Am J Sports Med 2000;28:687-694. 33. Powers CM: Rehabilitation of patel- lofemoral joint disorders: A critical re- view. J Orthop Sports Phys Ther 1998;28:345-354. 34. Crossley K, Bennell K, Green S, Mc- Connell J: A systematic review of physical interventions for patellofem- oral pain syndrome. Clin J Sport Med 2001;11:103-110. 35. Doucette SA, Goble EM: The effect of exercise on patellar tracking in lateral patellar compression syndrome. Am J Sports Med 1992;20:434-440. 36. Kannus P,Natri A, Paakkala T, Jarvin- en M: An outcome study of chronic patellofemoral pain syndrome: Seven- year follow-up of patients in a ran- domized, controlled trial. J Bone Joint Surg Am 1999;81:355-363. 37. Natri A, Kannus P, Jarvinen M: Which factors predictthe long-term outcome in chronic patellofemoral pain syn- drome? A 7-yr prospective follow-up study. Med Sci Sports Exerc 1998;30: 1572-1577. 38. Powers CM, Landel R, Sosnick T, et al: The effects of patellar taping on stride characteristics and joint mo- tion in subjects with patellofemoral pain. J Orthop Sports Phys Ther 1997;26:286-291. 39. Cowan SM, Bennell KL, Hodges PW: Therapeutic patellar taping changes the timing of vasti muscle activation in people with patellofemoral pain syndrome. Clin J Sport Med 2002;12: 339-347. 40. Crossley K, Bennell K, Green S, Cowan S, McConnell J: Physical ther- apy for patellofemoral pain: A ran- domized, double-blinded, placebo- controlled trial. Am J Sports Med 2002;30:857-865. 41. Federico DJ, Reider B: Results of iso- lated patellar debridement for patel- lofemoral pain in patients with nor- mal patellar alignment. Am J Sports Med 1997;25:663-669. 42. Owens BD, Stickles BJ, Balikian P, Busconi BD: Prospective analysis of radiofrequency versus mechanical de- bridement of isolated patellar chon- dral lesions. Arthroscopy 2002;18: 151-155. 43. Ryan A, Bertone AL, Kaeding CC, Backstrom KC, Weisbrode SE: The ef- fects of radiofrequency energy treat- ment on chondrocytes and matrix of fibrillated articular cartilage. Am J Sports Med 2003;31:386-391. 44. Betz RR, Magill JT III, Lonergan RP: The percutaneous lateral retinacular release. Am J Sports Med 1987;15: 477-482. 45. Christensen F, Soballe K, Snerum L: Treatment of chondromalacia patel- lae by lateral retinacular release of the patella. Clin Orthop 1988;234:145- 147. 46. Aderinto J, Cobb AG: Lateral release for patellofemoral arthritis. Arthros- copy 2002;18:399-403. 47. Shea KP, Fulkerson JP: Preoperative computed tomography scanning and arthroscopy in predicting outcome af- ter lateral retinacular release. Arthroscopy 1992;8:327-334. 48. O’Neill DB: Open lateral retinacular lengthening compared with arthro- scopic release: A prospective, ran- domized outcome study. J Bone Joint Surg Am 1997;79:1759-1769. 49. Marumoto JM, Jordan C, Akins R: A biomechanical comparison of lateral retinacular releases. Am J Sports Med 1995;23:151-155. 50. Fithian DC, Paxton E, Post W, Panni AS: Lateral retinacular release: A sur- vey of the International Patellofemo- ral Study Group. Arthroscopy 2004; 20:463-468. 51. Fulkerson JP: Diagnosis and treat- ment of patients with patellofemoral pain. Am J Sports Med 2002;30:447- 456. 52. Fulkerson JP: A clinical test for medi- al patella tracking (medial sublux- ation). Tech Orthop 1997;12:144. 53. Nonweiler DE, DeLee JC: The diagno- sis and treatment of medial sublux- ation of the patella after lateral reti- nacular release. Am J Sports Med 1994;22:680-686. 54. Hughston JC, Flandry F, Brinker MR, Terry GC, Mills JC III: Surgical correc- tion of medial subluxation of the pa- tella. Am J Sports Med 1996;24:486- 491. 55. Pidoriano AJ, Weinstein RN, Buuck Anterior Knee Pain 542 Journal of the American Academy of Orthopaedic Surgeons DA, Fulkerson JP: Correlation of pa- tellar articular lesions with results from anteromedial tibial tubercle transfer. Am J Sports Med 1997;25: 533-537. 56. Stetson WB, Friedman MJ, Fulkerson JP, Cheng M, Buuck D: Fracture of the proximal tibia with immediate weightbearing after a Fulkerson os- teotomy. Am J Sports Med 1997;25: 570-574. 57. Bellemans J, Cauwenberghs F, Brys P, Victor J, Fabry G: Fracture of the prox- imal tibia after Fulkerson anterome- dial tibial tubercle transfer: A report of four cases. Am J Sports Med 1998; 26:300-302. 58. Godde S, Rupp S, Dienst M, Seil R, Kohn D: Fracture of the proximal tibia six months after Fulkerson osteoto- my: A repor t of two cases. J Bone Joint Surg Br 2001;83:832-833. 59. Brittberg M, Lindahl A, Nilsson A, Ohlsson C, Isaksson O, Peterson L: Treatment of deep cartilage defects in the knee with autologous chondro- cyte transplantation. N Engl J Med 1994;331:889-895. 60. Peterson L, Minas T, Brittberg M, Nilsson A, Sjogren-Jansson E, Lindahl A: Two- to 9-year outcome after autol- ogous chondrocyte transplantation of the knee. Clin Orthop 2000;374:212- 234. 61. Minas T: Autologous chondrocyte implantation for focal chondral de- fects of the knee. Clin Orthop 2001; 391:S349-S361. 62. Peterson L, Brittberg M, Kiviranta I, Akerlund EL, Lindahl A: Autologous chondrocyte transplantation: Biome- chanics and long-term durability. Am J Sports Med 2002;30:2-12. 63. Knutsen G, Engebretsen L, Ludvigsen TC, et al: Autologous chondrocyte implantation compared with micro- fracture in the knee: A randomized trial. J Bone Joint Surg Am 2004;86: 455-464. 64. Argenson JN, Guillaume JM, Aubani- ac JM: Is there a place for patellofem- oral arthroplasty? Clin Orthop 1995; 321:162-167. 65. Kooijman HJ, Driessen AP, van Horn JR: Long-term results of patellofem- oral arthroplasty: A report of 56 ar- throplasties with 17 years of follow- up. J Bone Joint Surg Br 2003;85:836- 840. 66. Krajca-Radcliffe JB, Coker TP: Patel- lofemoral arthroplasty: A 2- to 18-year followup study. Clin Orthop 1996; 330:143-151. 67. Mont MA, Haas S, Mullick T, Hun- gerford DS: Total knee arthroplasty for patellofemoral arthritis. J Bone Joint Surg Am 2002;84:1977-1981. William R. Post, MD Volume 13, Number 8, December 2005 543