Initial Evaluation Of The Athlete With Anterior Knee Pain

INITIAL EVALUATION OF THE ATHLETE WITH ANTERIOR KNEE PAIN WILLIAM

L. D A V I S ,

JR, MD and JOHN

P. F U L K E R S O N ,

MD

Anterior knee pain is a common complaint among athletes and active, young individuals. Its causes are broad, but the correct diagnosis can usually be made after a thorough history and physical examination. The history should include a complete investigation of the nature and onset of the athlete's symptoms, past medical history, and the nature of any previous treatment he or she may have received for the problem. The physical examination includes a general lower extremity musculoskeletal examination with determinations of flexibility and limb alignment. The spine and hips are also evaluated to rule out radicular or referred pain to the knee. The knee examination must include assessment of the peripatellar tissues as well as the patellofemoral joint. Although patients often perceive their pain as being poorly localized,the pain source can usually be preciselylocalizedon examination.The information presented here should enable the clinicianto make an accurate diagnosis on which to base initial treatment. KEY WORDS: patellofemoral, pain, knee, anterior, athlete, evaluation, examination

Anterior knee pain is a common problem among athletes and active young patients. There are many causes, but a correct diagnosis can usually be made in most patients after a thorough history and physical examination. This article discusses the aspects of clinical evaluation that are most important in patients and athletes with anterior knee pain.

HISTORY Symptomatology

Onset. Athletes and active young people with anterior knee pain commonly present with symptoms that are chronic in duration and insidious in onset, and patients frequently have some component of overuse a n d / o r underlying malalignment. However, a more acute onset of symptoms after a traumatic episode may suggest patellar instability, a retinacular tear, or osteochondral injury, depending on the mechanism. An indirect mechanism consisting of a strong quadriceps contraction, a flexed and valgus knee position, and internal rotation of the femur on the tibia is a common one for patellar dislocation. The classic example of this is a baseball batter swinging and missing a pitch. Such patients frequently report seeing their kneecap "off to the side," which either spontaneously reduces or requires manipulation. A direct mechanism, such as contact with another player, can result in a chondral lesion from direct trauma to the patella or distal femur. Many patellar crush injuries occur with the knee flexed so that the lesion involves the proximal pole of the patella. In the setting of a posteriorly directed force to the knee, one must From the Universityof Connecticut School of Medicine, Farmington, CT and OrthopedicAssociates of Hartford, PC, Hartford, CT. Address reprint requests to John P. Fulkerson, MD, Clinical Professor, University of Connecticut School of Medicine, Orthopedic Associates of Hartford, PC, 270 Farmington Avenue, Suite 364, Farmington, CT 06032. Copyright © 1999 by W.B. Saunders Company 1060-1872/0702-0002510.00/0

also be aware of the potential of posterior instability and secondary patellofemoral symptoms from increased compressive forces across the joint. Pain. The patient should be asked to point to the location of the pain. Knee pain diagrams (Fig 1) can be helpful and have been shown to be accurate in predicting areas of tenderness on physical examination. 1 Other characteristics of the patient's pain that should be specifically addressed include quality, radiation, and exacerbating and relieving factors. In addressing these characteristics, the clinician should be able to differentiate somatic pain from pain that is referred or radicular in nature. Anterior knee pain is frequently reported by patients to be poorly localized, positional, and activity-related. It is usually relieved by passive extension and exacerbated by prolonged flexion (the "movie theater sign") because of increased tension in the extensor mechanism as wetl as the posterior and lateral forces imparted by the retinacular attachments of the iliotibial band, which is posterior to the knee axis in flexion greater than 30 °. It is also exacerbated by stair climbing and, particularly, descending stairs, because of the strong, eccentric quadriceps contractions that are required. Ask the athlete if pain is experienced with any particular sport-specific activities to gain an understanding of how pain is produced. In contrast, pain that is constant a n d / o r not related to activity or knee position should make the clinician suspicious of referred pain, neurogenic pain, or reflex sympathetic dystrophy (RSD). Referred pain from the hip typically affects the anterior distal thigh and knee, and, therefore, a history of hip problems should be sought. Pain with a burning quality is also suggestive of neurogenic pain or RSD. Associated numbness or tingling suggests a neuroma (especially if the pain is located below a scar) or a radicular problem. All patients should be asked if they have any hip or low back pain. Pain that is sharp, intermittent, or unpredictable is characteristic of loose bodies or an unstable chondral flap.

Operative Techniques in Sports Medicine, Vol 7, No 2 (April), 1999: pp 55-58

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cal therapy has been tried, it is important to investigate precisely what was done to determine if it was appropriately prescribed and followed through by the patient and therapist. If the patient underwent previous surgery, a copy of the operative report, or, ideally, arthroscopic photos should be obtained. The patient should be asked if the procedure(s) had any effect on his or her symptoms, and, particularly, if there was a change in the nature of the pain.

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Fig 1. Matched patient and physician pain diagrams showing good correlation. (Reprinted with permission. 1) Instability. Patients with anterior knee pain commonly complain of instability or "giving way." It is important t o determine if this feeling of instability is related to the extensor mechanism or secondary to ligamentous insufficiency. This will be largely determined by physical examination. However, a lack of knee trauma will usually rule out cruciate or collateral ligament pathology. Instability related to the extensor mechanism may either be secondary to malalignment, quadriceps insufficiency from long-term deconditioning, previous surgery, or muscular inhibition resulting from pain or effusion (the patient will say the knee "goes out" or "gives way" for either the reflex quadriceps inhibition because of sudden pain or the true momentary patellar dislocation. It is the clinician's task to differentiate the two). A history of patellar dislocation should also be sought to determine if the patient has true patellar instability. Other symptoms. Crepitus or a grinding sensation under the kneecap is a common complaint and usually implies some degree of chondromalacia involving the patella a n d / o r femoral trochlea. However, this should be differentiated from a complaint of a snapping sensation, which is more consistent with a pathologic plica. A sensation of locking may be attributable to chondral or meniscal pathology. A history of swelling, although nonspecific, is important to investigate. If attributable to an effusion, it suggests intra-articular (rather than peripatellar) pathology. If the swelling followed trauma to the knee, it likely represents hemarthrosis. However, it frequently arises insidiously and indicates inflammation--either from a pathologic plica or in reaction to articular cartilage debris.

Previous Treatment It is helpful to know what prior treatment patients received (bracing, taping, nonsteroidal anti-inflammatory drugs, injections, physical therapy) for their knee problems and whether or not the interventions were successful. If physi56

Past medical history The majority of athletes who present with anterior knee pain are otherwise healthy. However, it is important to determine if there is a personal or family history of any problems that commonly cause musculoskeletal pain (gout and inflammatory arthritides, sickle cell disease, etc. Patellofemoral disorders show a strong familial pattern). The patient should also be asked if other joints are symptomatic. Medications should be noted, including the use of corticosteroids (possibly for asthma in an athlete) or narcotics on a chronic basis. In younger athletes, a recent growth spurt can cause increased tension in the extensor mechanism because of the "lag" of its growth relative to the skeleton. This can result in overuse problems such as quadriceps and pate]Jar tendinitis, or Osgood-Schlatter's disease. Always consider the possibility of gout or Lyme disease.

PHYSICAL EXAMINATION General

The patient should be dressed so that both lower extremities are visible in their entirety. One should note the patient's body habitus and any evidence of general deconditioning or atrophy of the involved lower extremity. The gait and overall limb alignment should be carefully analyzed, noting any excessive pronation or genu valgum. The range of motion of all lower extremity joints should be recorded, because patellofemoral problems are frequently associated with flexibility defecits. In contrast, general ligamentous laxity may be suggestive of patellar subluxation, and, therefore, should be ruled out. The hips should be examined initially with the patient in the supine position. A hip flexion contracture must be ruled out, because it can result in increased knee flexion during gait and an abnormally high patellofemoral joint reaction force. Increased internal rotation may be secondary to excessive femoral anteversion, which can be associated with patellar subluxation. Decreased internal rotation (typical of osteoarthritis) and pain on hip motion may imply inarticular pathology and referred pain to the knee. The popliteal angle should be measured and should be between 160 ° and 180 ° in young athletes. A measurement less than this may be indicative of hamstring tightness, which necessitates increased quadriceps force when extending the knee, and, therefore, an abnormally high patellofemoral joint reaction force. Hamstring tightness is also associated with spondylolisthesis, which should be suspected in athletes, such as gymnasts, who are involved in frequent lumbar spine hyperextension. A straight leg raise should be performed to rule out the possibility of a herniated nucleus pulposus. DAVIS AND FULKERSON

Knee

A complete knee examination should always be performed, including tests for ligamentous instability and meniscal pathology. We will focus on that which pertains to evaluating the athlete with anterior knee pain. During initial inspection of the knee, one should note the condition of the skin, including any previous incisions. It should be determined through ballottement of the patella whether any swelling is a local phenomenon or attributable to effusion. Knee range of motion should be measured initially with the patient in the supine position. Full active and passive extension should be achieved, and flexion should be compared with the uninvolved side, because it may vary with body habitus. The patient should be turned to the prone position to appropriately assess extensor mechanism flexibility, because the rectus femoris crosses the hip (Fig 2). In most athletes, knee flexion in this position will allow the heel to touch the buttock. Inability to do this, or asymmetry on examination may indicate excessive tension in the extensor mechanism, and this maneuver wilt frequently be associated with pain in such patients. Hip rotation can be reassessed while the patient is prone. The knee should be palpated in an attempt to reproduce and determine the source of the patient's pain. By doing so, one should be able to quickly determine whether or not the patient's problem is attributable to extensor mechanism a n d / o r patellofemoral pathology. It should be noted whether the patient's responses to palpation are appropriate or suggestive of reflex sympathetic dystrophy, psychiatric pathology, or secondary gain issues. The innervated tissues of the anterior knee include patellar and quadriceps tendons; synovium, plicae, and bursae; subchondral bone of the patella and trochlea; and retinacular soft tissues. Patellar tendinitis (jumper's knee) is more common than quadriceps tendinitis. Tenderness is usually elicited at the inferior pole of the patella in patients with this problem. The distal quadriceps tendon should also be palpated. The prepatellar, infrapatellar, and pes anserine bursae should be palpated to ruie out bursitis. Palpating the articular surfaces of the patella and trochlea necessitates compression of the intervening retinaculum and synovium, and, therefore, is usually not helpful. However, the examiner's

Fig 2. Extensor mechanism flexibility should be measured in the prone position. Note elevation of the pelvis attributable to hip flexion in this patient with severe knee extensor mechanism tightness. EVALUATION OF ATHLETES WITH ANTERIOR KNEE PAIN

hand should be placed over the patella during knee range of motion to detect any crepitus from the patellofemoral joint that may present. It is important to note the degree of flexion during which crepitus is elicited, because it is usually indicative of the location of a patellar chondral defect or abnormality. Crepitus early in flexion implies distal pole involvement, and crepitus late in flexion implies proximal pole involvement. Patellofemoral crepitus should be easily differentiated from a pathologic plica, which is usually medial to the patella and palpable as a band snapping over the femoral condyle. The retinaculum should be carefully palpated. Lateral retinacular pain and tenderness is common in patients with patellofemoral malalignment. In a prospective study of 60 young, active patients, 90% experienced pain in some portion of the lateral retinaculum, usually at or near the retinaculopatellar junction. 2 The cause of the pain in these patients has been shown to be nerve demyelination and fibrosis, similar to what is seen in Morton's neuroma. 3 Patellofemoral mechanics should be analyzed. The Q-angle should be measured to serve as an estimate of the lateral moment on the patella° It is measured as the angle formed between a line joining the anterior superior iliac spine and center of the patella, and a line from the patella to the tibial tubercle. A normal Q-angle is generally considered to be less than 15 ° in females and less than 10 ° to 12 ° in males. Some believe that the Q-angle is not an accurate tool for determining patellar alignment because it is measured in extension, and a laterally subluxed patella will yield a falsely low measurement. Therefore, Kolowich et al 4 believe that the tubercle-sulcus angle measured at 90 ° of flexion is a more accurate assessment of the quadriceps vector. It is defined by the angle between a line from the center of the patella to the center of the tibial tubercle and a line perpendicular to the transepicondylar axis. A tuberclesulcus angle of 0 ° is considered normal, and more than 10 ° is considered abnormal. Patellar tracking should be visualized through the full range of motion of the knee. The patella should smoothly enter and leave the femoral trochlea on flexion and extension, respectively. A sudden lateral motion of the patella on extension has been named the J-sign and is seen in patients with lateral patellar instability. These patients usually have excessive lateral patellar glide and a positive apprehenston test. Patellar glide is assessed by passively translating the patella medially and laterally with the knee in full extension. The patella is visually divided into four longitudinal quadrants. The amount of glide is reported as the number of quadrants of translation that is achieved. One quadrant or less of translation is usually indicative of tight, passive restraints, and three or greater indicates hypermobility or incompetent restraints. A positive apprehension test is indicative of patellar instability and is elicited when the patient shows pain and guarding on passive lateral translation of the patella. Medial patellar instability is much less common than lateral instability, but should be ruled out, especially in patients who remain symptomatic after previous realignment procedures. Fulkerson 5 described a test for medial subluxation that involves holding the patella medially as the patient's knee is passively flexed (Fig 3). Pain and 57

Fig 3. Medial subluxation test. (A) Medial pressure is applied to the patella with the knee in full extension. (B) The knee is then passively flexed, Reproduction of the patient's symptoms indicates a positive test,

reproduction of the patient's symptoms represent a positive test. W h e n an impression of medial or lateral patellar instability is established, the examiner m a y confirm the diagnosis by applying a Trupull brace (Depuy-Orthotech, Tracy, CA) to correct the problem and see if the patient experiences relief (Fig 4). Patients with patellofemoral dysfunction m a y have patellar tilt w i t h o u t subluxation. This is because of a tight lateral retinaculum and is referred to as excessive lateral pressure syndrome. It is assessed with the patellar tilt test. In normal knees, the patella can be passively elevated from the lateral side with the knee in full extension so that it is parallel to or tilted slightly b e y o n d the horizontal plane.

DIFFERENTIAL DIAGNOSIS After the history and physical examination, the physician should be able to determine, first, whether the pain the patient is experiencing is referred, radicular, or somatic in nature. For true anterior knee pain, the next step is to

categorize the cause as peripatellar or patellofemoral. Peripatellar syndromes include synovial abnormalities (pathologic plicae, bursitides), retinacular strain, iliotibial band friction syndrome, and extensor mechanism overuse syndromes (patellar and quadriceps tendonitis, retinacular strain, iliotibial band strain, Osgood-Schlatter disease, Sinding-Larsen-Johansson disease). These diagnoses can be fairly easily differentiated through palpation on physical examination. If the athlete has a patellofemoral problem, it m a y be one of patellar instability (subluxation or recurrent dislocation), tilt (excessive lateral pressure syndrome), or arthrosis (degenerative or delaminating lesion involving the patella a n d / o r femoral trochlea). Instability and tilt can coexist and are determined by assessing limb alignment and rotation, patellar tracking, pateUar glide, and patellar tilt. Patellofemoral arthrosis m a y become manifest on physical examination as painful patellar crepitus on knee range of motion with compression of the patella.

SUMMARY Anterior knee pain is c o m m o n in athletes and active individuals, and the causes are fairly broad. However, by performing a thorough history and physical examination, the clinician should be able to make the correct diagnosis.

REFERENCES

Fig 4. A Trupull brace (DePuy Orthotech, Tracy, CA) may be applied to correct either medial or lateral subluxation. The diagnosis is confirmed if symptoms are relieved.

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1. Post WR, Fulkerson J: Knee pain diagrams: Correlation with physical examination findings in patients with anterior knee pain. Arthroscopy 10:618-623, 1994 2. Fulkerson JP: The etiology of patellofemoral pain in young, active patients: A prospective study. Clin Orthop 179:129-133, 1983 3. Fulkerson JP, Tennant R, Jaivin JS, et al: Histologic evidence of retinacular nerve injury associatedwith patellofemoralmalalignment. Clin Orthop 197:196-205, 1985 4. Kolowich PA, Paulos LE, Rosenberg TD, et al: Lateral release of the patella: Indications and contraindications. Am J Sports Med 18:359365, 1990 5. Fulkerson JP: A clinical test for medial patella tracking (medial subluxafion).TechOrthop 12:144, 1997.

DAVIS AND FULKERSON