Injured or Arthritic Knees: Evaluating Patellofemoral and Tibiofemoral Articulation
ABSTRACT: Palpate the entire retinaculum, retropatellar surface, and trochlear grooves when examining the patellofemoral articulation in a patient with an injured or arthritic knee. Various manipulations of the patella reveal retinacular tightness, instability, or symptomatic chondromalacia. A tight lateral retinaculum or an increased quadriceps (Q) angle predisposes to patellar maltracking and subluxation. Always check range of motion. The absence of a normal degree of recurvatum indicates intra-articular pathology, such as osteoarthritis, displaced meniscal tear, torn anterior cruciate ligament, loose body, or osteochondral fracture. In addition to careful palpation of the joint line, the manipulations of the Steinmann test and the modified McMurray test, plus the Apley grind and distraction tests, aid in assessing the menisci.
Key words: knee, physical examination, patellofemoral articulation, tibiofemoral articulation
The knee is one of the most commonly injured joints in the body and is also frequently affected by arthritis. In a previous article (CONSULTANT, May 2013, page 354), we considered the anatomy of the knee, key diagnostic details garnered from the history, and impressions gained following your initial observation.
After you have taken a thorough history, you should be able to start formulating a differential diagnosis to guide the physical examination. Here, we discuss the specifics of examination of the patellofemoral and tibiofemoral articulations, stressing careful palpation of all structures and use of several provocative tests. In a future article, we will discuss assessment of the ligamentous structures.
PATELLOFEMORAL ARTICULATION
Palpation. Begin by palpating the medial and lateral retinacula (the soft-tissue support on either side of the patella). Take care, however, not to push so hard that pressure is also exerted on the trochlear groove of the femur, which may also be tender. The lateral retinaculum may be sensitive in patients with symptomatic lateral patellar tilt (the excessive lateral pressure syndrome).1 The medial retinaculum may be sore in those with lateral patellar subluxation/dislocation, which results in stretching or tearing of this patellar support.
Palpate the entire retinaculum and determine the location of any tenderness. To avoid palpating the retropatellar surface, be careful not to displace the patella to either side while performing this examination.2
After examination of the retinaculum, palpate the retropatellar surface. With your thumb, gently push the patella aside in each direction, exposing the medial and lateral patellar facets. Tenderness may indicate chondromalacia. Although chondromalacia is a diagnosis made pathologically, not clinically, we use it here in its more commonly understood sense of cartilage breakdown or roughening, which may or may not be associated with mechanical malalignment.
Palpation of the medial and lateral trochlear grooves may also elicit tenderness. Patellofemoral dislocation leads to collision of the medial patellar facet against the lateral trochlear groove; either may be tender following this injury. Sometimes, patellofemoral dislocation may even lead to an osteochondral fracture.
A plica can occasionally be palpated medial and slightly inferior to the patella. It feels like a rubbery knob and may snap as it tracks over the medial femoral condyle. You may be able to demonstrate this by passively flexing and extending the patient’s knee while holding the tibia in internal rotation and valgus. With the palm of your hand, displace the patella slightly medially while your fingers palpate any plicae snapping over the area of the medial femoral condyle.3
Patellofemoral grind test. This is an excellent test to reproduce patellofemoral pain. Ask the patient to contract the quadriceps while, with one or two fingers, you push the patella distally and compress it gently against the trochlear groove. Since this manipulation may trap synovium between the patella and femoral groove, it may elicit pain even in normal knees. The specificity of the test may be increased, however, by asking the patient whether any pain felt reproduces the symptoms or whether it simply is a new pain that you have caused. We prefer this method because it is the more sensitive test.
Another reliable method of performing this test is to position the patient’s knee at 30 degrees of relaxed flexion (eg, over a pillow or the opposite leg), so that the patella is in the trochlear groove. Then compress the patella medially and laterally. This motion should not produce pain in a normal knee.4 If the patient is unable to achieve relaxed flexion, carry out the test by placing the knee in fully relaxed extension.
Lateral retinacular tightness (patellar tilt) test. With the patient’s knee extended, the quadriceps relaxed, and the transepicondylar axis parallel to the floor, lift the lateral edge of the patella from the lateral femoral condyle. If you are unable to raise the patella horizontally (so that the lateral edge is even with the medial edge), the lateral retinaculum is tight.5 Excessive lateral retinacular tightness may lead to patellar tilt and chondromalacia on the lateral side of the patellofemoral articulation.5,6
Patellofemoral apprehension test. With the patient’s knee fully extended, gently push the patella laterally. Be alert for signs of apprehension—specifically the patient’s feeling of alarm or impending dislocation, which is consistent with lateral patellofemoral instability.
Patellar glide. This test helps evaluate the medial and lateral retinacular structures. If the patient has not undergone knee surgery, the usual pathologic abnormality is an overly tight lateral retinaculum and an overly lax medial retinaculum. Support the patient’s knee in 20 to 30 degrees of flexion by resting the thigh over your own knee or a small pillow. With the patient’s quadriceps relaxed, push the patella medially and laterally. Mentally, divide the patella into four quarters, from medial to lateral. A patella that has a normal degree of mobility should translate roughly two quarters in either direction.
Lateral glide of three quarters suggests an incompetent medial restraint, and lateral glide of four (indicating a patella that may become dislocated) signifies a deficient medial restraint. In the latter case, the patient usually experiences apprehension with the lateral glide, as described above.
Medial glide of one quarter or less denotes lateral retinacular tightness and often correlates with a negative passive patellar tilt. A medial glide of three or four quarters suggests a hypermobile patella.5 A tight lateral retinaculum (diagnosed by the patellar glide and tilt tests) with palpable tenderness, combined with appropriate symptoms and patellar tilt, is consistent with a diagnosis of the excessive lateral pressure syndrome.1,7
Quadriceps (Q) angle. This is the angle formed between the anterior superior iliac spine of the pelvis, the center of the patella, and the center of the tibial tubercle. The larger the Q angle, the larger the lateral vector acting on the patella, possibly predisposing to maltracking, subluxation, and patellofemoral instability.
Although it is classically measured in extension, the Q angle is probably more accurately measured with the patient seated and the knee flexed at 90 degrees, because most patellas are centralized within the trochlea at this angle. The Q angle measured at 90 degrees is a clinically useful variant of the tubercle-sulcus angle described by Kolowich and colleagues.5 Because rotation of the foot can also affect this measurement, allow the patient’s foot to hang comfortably over the edge of the examination table. When the leg is in extension, the Q angle may appear falsely normal in a patient who has a pathologically subluxed lateral patella.
At 90 degrees of knee flexion, the Q angle should be nearly straight (ie, 0 degrees). An angle of 10 degrees or more is definitely abnormal. (With the leg extended and the quadriceps muscle contracted, anything greater than 10 to 15 degrees is abnormal.3,5)
Lateral pull sign. This is a test of the functional Q angle, or the dynamic pull of the quadriceps. With the knee extended, ask the patient to contract the quadriceps. In a normally tracking patella, the proximal movement is equal to or greater than the lateral movement. Lateral movement that exceeds the proximal movement reflects an abnormal lateral quadriceps vector acting on the patella. The cause could be atrophy of the vastus medialis obliquus or hypertrophy of the vastus lateralis; either of these conditions can be observed.5
Patellofemoral tracking. This movement is best assessed by having the seated patient actively flex and extend the knee. Look for a “J” sign (so called because the path of the patella looks like an upside-down J), which indicates lateral movement of the patella at terminal extension.
Dynamic patellofemoral crepitus. Palpate the patella while the patient actively flexes and extends the knee. The presence of crepitus is abnormal and usually represents chondromalacia, but it may also indicate the presence of synovial fringes that have become interposed between the patella and femur. Minor crepitus is common among older patients and may be insignificant, unless it is painful. Deep–knee bending magnifies any crepitus present.6
Patella alta (abnormal proximal position of the patella). You can note patella alta as the patient sits on the edge of the examination table. With the knee flexed at 90 degrees, the patient should be situated on the distal end of the femur. The patella’s proximal pole should be nearly in line with the anterior femoral cortex and its anterior pole in line with the femoral shaft. Thus, the normally aligned patella points to the opposite wall or to the wall’s junction with the ceiling.
If the kneecap sits more on the anterior than the distal surface of the femur and therefore points straight to the ceiling, suspect patella alta, the many gradations of which range from mild through severe.3 Patella alta predisposes the patient to patellofemoral instability and can be confirmed with an x-ray study.6
Functional reproduction of patellofemoral symptoms. Patellofemoral symptoms may be reproduced by having the patient step down from a step stool and then back up or by walking in a half squat. Full squatting and walking while squatting (“duckwalking”) also elicit discomfort, but this will be especially painful to patients with meniscal problems.
RANGE OF MOTION
Recurvatum. Although range-of-motion measurements for normal knees are often given as 0 to 135 degrees, almost all knees generally go into some amount of recurvatum—usually 4 to 7 degrees. It is important to check for this, because the absence of recurvatum—especially in comparison with the opposite knee—is really a functional flexion contracture. This loss of extension may predispose osteoarthritic patients to further tibiofemoral and patellofemoral wear and symptoms, and it may also lead to postsurgical morbidity. The absence of a normal degree of recurvatum indicates intra-articular pathology, such as osteoarthritis, displaced meniscal tear, torn anterior
cruciate ligament, loose body, or osteochondral fracture.
To best evaluate recurvatum, have the patient lie supine while you hold the distal end of the thigh firmly against the table and raise the ipsilateral heel. Measure the distance from the heel to the table (in centimeters or finger-breadths). Repeat this maneuver with the opposite leg and compare the measurements.
Flexion deficiencies. These are also best noted by comparing one leg with the other. In this case, measure and compare the distance between the heel and the buttock at full flexion and note any discrepancies. Loss of flexion in chronic situations usually reflects chondromalacia patellae or generalized knee osteoarthritis.
The acute loss of motion after an injury is significant. It usually represents an incarcerated meniscal tear, although occasionally it can be caused by patellofemoral subluxation,6 tense effusion, or osteochondral fracture. Lidocaine injection and aspiration are diagnostic when effusion is the cause and will make the patient far more comfortable.
TIBIOFEMORAL ARTICULATION
Palpation. Elicitation of point tenderness by palpation is often the most significant part of the physical examination. Once you know the location of the pain, you have only to apply your knowledge of anatomy to determine the potentially injured structures and formulate a differential diagnosis. Provocative tests may then confirm the diagnosis, often identifying the specific structure injured.
Once you have taken a detailed history, observed the patient’s gait and alignment, and checked for effusion and atrophy (as described in our previous article), the subsequent order of the physical examination is a matter of personal preference. We recommend examining the patellofemoral articulation first, then range of motion, and finally tibiofemoral articulation. This sequence minimizes manipulation of a possibly painful knee. In general, start palpating nonpainful areas and finish at the symptomatic region.
For example, assuming radiographic films show no abnormalities, pain along the middle third of the medial joint line may represent an interstitial injury of the medial collateral ligament (MCL), a capsular injury, or a medial meniscal tear. Once you have narrowed the differential diagnosis by palpation, the appropriate provocative tests (valgus stress, the McMurray examination, and the Apley compression and grind tests) can help determine the precise diagnosis.
The tibiofemoral joint is most easily palpated while the patient is supine or seated, with the knee flexed 90 degrees. As with the entire knee examination, maintain a consistent order of palpation to avoid errors of omission.
Tibial tubercle. In a young teenager, tenderness of the tibial tubercle is consistent with a diagnosis of Osgood-Schlatter disease (Figure).
Figure – this radiograph of the right knee of a 17-year-old boy with osgood-schlatter disease shows fragmentation and irregularity of the outline of the tibial tuberosity with soft tissue swelling.(Courtesy of Edmond K. H. Liu, MD, and Alexander K. C. Leung, MD.)
Midsection of patellar ligament. Tenderness here, rather than at the ligament’s origin (at the inferior pole of the patella) or its insertion (into the tibial tubercle), usually represents patellar tendinosus, peritendinitis, or both. Tenderness below the joint line may indicate superficial infrapatellar bursitis (the bursa superficial to the patellar ligament) or deep infrapatellar bursitis (the bursa deep to the patellar ligament).
Tenderness of the ligament associated with superficial swelling over the patella may be caused by prepatellar bursitis. Bursitis over the anterior knee, known as housemaid’s knee, is most common among patients who spend a great deal of time kneeling. Tenderness behind the patellar ligament at the joint line may represent irritation of the retropatellar fat pad on either side of the patellar ligament. This may be a source of anterior knee pain, the so-called fat pad syndrome.2,8
Inferior pole of patella. In a young teenager, tenderness in this area indicates Sinding-Larsen-Johansson syndrome (traction spurs). Tenderness of the patella in young athletes who jump may occasionally represent a stress fracture.
Pes anserinus. Located on the anterior proximal tibia, just medial to the distal tibial tubercle, the pes anserinus is the insertion site of the sartorius, gracilis, and semitendinosus tendons and is covered with a bursa. Suspect pes anserine bursitis if you find tenderness here, but rule out a strained MCL (which passes beneath the posterior pes) before diagnosing simple bursitis.
Anterior surfaces of medial and lateral femoral condyles. These areas can be palpated with the patient’s knee flexed. Tenderness in these locations may indicate an osteochondral fracture, osteonecrosis, osteochondritis dissecans, or chondromalacia.
Medial femoral epicondyle. This protuberance serves as the origin for the MCL, which should be palpated from this site to its insertion on the proximal medial metaphyseal flare of the tibia. The MCL covers the middle third of the medial joint line. Although tenderness is consistent with a strain, take care to differentiate tenderness of the interstitial MCL from that of the medial joint line; the latter is associated with medial meniscal tears. These two conditions can often be differentiated by the patient’s history and by carrying out provocative testing. The distal MCL is covered by a bursa, which may also be a source of tenderness.
Fibular collateral ligament (FCL). Best palpated with the knee in a flexed, figure-4 position, the FCL feels like a tight cord extending proximally from the fibular head. Palpate along its entire length.
Lateral epicondyle. Tenderness here may be caused by FCL strain or by the iliotibial band syndrome. It may also be caused by iliotibial band tendinosis resulting from overuse. In iliotibial band syndrome, which is one of many overuse syndromes, the iliotibial band is excessively tight and rubs over the lateral epicondyle. You can feel this rubbing with flexion and extension of the knee. Gerdy’s tubercle may also be tender in patients with this syndrome.9 Check also for abnormal motion of the fibular head to rule out injury to the proximal tibiofibular joint.
Posterior structures. Extend your palpation posteriorly to include the hamstring and the popliteus tendon. Roll your finger over the latter structure; if this reproduces the patient’s pain, popliteal tendinitis is indicated. If the posterior joint capsule is tender, it may have been stretched or torn following a hyperextension or posterior translation injury. Posterior knee pain without posterior tenderness suggests referred patellofemoral pain.
Joint lines. Palpate both joint lines completely, taking care to examine the entire posterior aspect. Medial meniscal tears usually lead to tenderness in the posteromedial “soft spot,” just posterior to the MCL. This area may be palpated better with the knee in the figure-4 position or by externally rotating the tibia.8
Differentiate posterior medial joint-line tenderness from that found at the insertion of the semimembranous muscle, which is only a centimeter distal to the posteromedial joint line. Anterior medial joint-line tenderness is usually related to patellofemoral pain,6 not meniscal problems.
Menisci. Lateral meniscal tears usually cause posterior joint-line tenderness. In contrast to medial meniscal tears, however, they may also cause anterior joint-line pain.6 Meniscal tears cause pain by pulling on the adjacent synovium as they impinge on the tibiofemoral joint. Therefore, results of physical examination following meniscal injuries may vary greatly with time, depending on the degree of inflammation of the surrounding synovium. Normal examination findings do not rule out a meniscal tear. A repeated examination at a later date, after pre-examination exercise has been used to exacerbate symptoms, may demonstrate marked joint-line tenderness, effusion, and positive provocative meniscal test results (Box).
Make the diagnosis of meniscal injury by combining the history (mechanical symptoms such as locking, extension blocking, effusion, giving way, and catching) and physical examination findings (effusion, focal joint-line tenderness), as well as positive results of provocative tests. The reliability of these tests is increased if the patient’s history suggests a high probability of meniscal injury. ■
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