chapter 3: History and Physical Examination
Evidence of Malalignment
STANDING ALIGNMENT EXAMINATION
Examination begins with the patient standing facing the examiner, barefoot in shorts. Examine for atrophy, extremity alignment including Q angle, pelvic obliquity/limb length, foot type, gait, and the ability to squat and rise smoothly to the standing position.
Atrophy. Observe for evidence of quadriceps atrophy. Measurement of thigh circumference at standard distances from the superior pole of the patella and compare side to side. Do not focus just on the quadriceps, but consider the possibility of atrophy involving the entire extremity as a sign of proximal denervation, extreme disuse, or neuromuscular disease.
Quadriceps weakness implied by atrophy is very important because dynamic muscular control of the patella is so vital to patellar stability. The vastus medialis obliquus (VMO) resists lateral patellar tilt and subluxation. In addition to providing dynamic medial stability, the quadriceps provides shock absorption for the knee joint during weightbearing as it eccentrically resists collapse of the knee into flexion. The function of the quadriceps as a shock absorber is well illustrated by considering the loads imposed by weight acceptance while descending stairs. As weight is transferred to the downstairs foot, the quadriceps must fire while the knee is flexing to prevent the knee from collapsing. Controlled eccentric contraction allows further knee flexion to lower body weight smoothly to the next step. When the quadriceps is weak and fails in its role as a shock absorber, patellofemoral loads may increase. Not only may loads be increased, but if the VMO is relatively deficient, the patella may be somewhat malaligned and the articular surfaces somewhat incongruent while accepting the increased load. Not surprisingly, many quadriceps deficient patients with patellofemoral disorders have pain while descending stairs. Atrophy indicates a need to make quadriceps strengthening a treatment priority.
Q Angle. The Q angle is the angle formed between a line from the anterior superior iliac spine to the center of the patella and a line from the center of the patella to the tibial tubercle (Fig. 3.2).
Rationale‑Q Angle. The Q angle is frequently discussed as a reflection of the valgus angle of the extensor mechanism. Insall initially described examination for Q angle with the patient supine (10). Woodland and Francis (8) demonstrated that Q‑angle measurements are slightly but significantly greater in standing subjects. Olerud and Berg showed that foot position affects the standing Q‑angle measurements (9). Their study emphasized the need to standardize foot position during Q‑angle measurement because internal rotation of the foot and pronation both increased the Q angle. Logically, it seems that standing measurement would reflect weightbearing function more accurately.
Insall's recommendation of 20 degrees as an upper limit for a normal Q angle has been widely quoted but may not stand up to a review of available literature. This recommendation appears to be based on a personal communication from James and their preliminary study of 50 normal knees with an average Q angle of 14 degrees and variation of "no more than a few degrees" (10). Normal populations have been measured and the results are summarized in Table 3.1 (8, 10‑14). Investigators have agreed that female subjects generally have greater Q angles.
The underlying assumption is that the larger the Q angle is, the larger the lateral moment on the patella. Insall found that 48% of his patients with chondromalacia had Q angles greater than 20 degrees. Aglietti noted that no healthy men had supine Q angles of 20 degrees or greater but 15% of asymptomatic women did (15). Conversely, 40% of patients who were symptomatic had Q angles of 20 degrees or more. Stated in the opposite way, 60% of Aglietti's patients and 52% of Insall's patients with patellofemoral pain had Q angles within even their original empiric definition of normal. Among patients with recurrent subluxation in Aglietti's report, the Q angle was not significantly different from the control subjects. Fairbanks demonstrated, however, that there was no significant difference in Q angles between 310 adolescent male and female subjects without knee pain and the 136 who had some knee pain within the previous year. The Q angle has not been shown to predict patellofemoral symptoms.
One of the theoretical concerns with using the Q angle as an estimate of the lateral moment of the extensor force is that as the patella subluxates laterally, the Q angle decreases. In other words, lateral subluxation masks the measurement that is designed to evaluate it. Fithian et al attempted to address this concern by measuring the Q angle with the knee in 30 degrees of flexion with the patella manually reduced into the trochlea (16). Using this technique, they did find higher angles in 22 patients with history of patellar dislocation. It is interesting that contralateral uninvolved knees also had higher Q angles compared with their normal population of 94 control subjects. This modified Q‑angle measurement may not accurately represent a dynamic vector either because reduction of the patella into the trochlea depends on adequate patellar mobility. Kujala et al compared Q angles measured at 0 and 30 degrees and found a change of ‑6.0 degrees as the knee was flexed (17). Although it has been said that derotation of the tibia is less than normal in patients with patellofemoral pain (18), the decrease in Q angle in Kujala's study was identical for 34 asymptomatic army recruits and 28 with exertional anterior knee pain. Although interesting, further studies are necessary before endorsing the evaluation of the Q angle in 30 degrees of flexion.
In summary, Q‑angle measurements are widely discussed but no direct correlation with the incidence of patellofemoral disorders is well established by scientific criteria. The range of normal values established by multiple studies is wide. Although some authors have used Q angles as part of criteria to determine realignment strategies, such approaches are empirical (19, 20). Should the Q angle even be measured? Understanding the theoretical importance of the degree of valgus extensor moment is important. The Q angle is presumably one method of estimating the lateral moment acting on the patella. But one must remember no solid data links specific Q‑angle measurements to diagnosis or results of treatment. Although a traditional part of patellofemoral discussion, actual clinical utility of the Q angle is uncertain despite extensive study.
Leg Length Measurement. Screen for leg length equality by palpating the top of the iliac crest and comparing sides (Fig. 3.3). If inequality exists and measurement is desired, level the pelvis by having the patient stand on an object of known height such as standardized blocks.
Leg length difference results in abnormal gait and may be associated with patellofemoral pain in the short leg. A short limb results in ipsilateral pelvic drop in terminal swing phase causing an increased valgus moment at the knee (21). Length difference greater than 1/2 inch (12.5 mm) occurs in 4 to 8% of normal controls and has been correlated with an increased incidence of low back pain (22, 23). Although no studies link leg length inequality with anterior knee pain, it is logical to correct length differences in symptomatic extremities with heel lifts in the hope of reducing or eliminating aggravating stress.
Foot Type, Alignment, Gait. Ask the patient to turn around and observe both feet for excessive pronation and associated hindfoot valgus (Fig. 3.4). If the patient has excessive pronation, ask him/her to stand on his/her toes and see if pronation is flexible. Ask the patient to walk. Watch for excessive and prolonged pronation and abnormal valgus or varus moments at the knee.
Why to Do It. Judge pronation during weightbearing. Evaluation of standing heel position has been shown to be reproducible and is a good screening tool for pronation (24). Valgus hindfoot position generally indicates hindfoot pronation and simply having the patient stand on their toes quickly defines whether the flatfoot is rigid or supple. If the pronation is flexible it will reverse when the patient stands on their toes. Observation of the hindfoot and arch during standing and walking seems adequate for clinical estimation of the degree of pronation.
Excessive and prolonged hindfoot pronation produces obligatory internal tibial rotation (25). The hindfoot normally pronates from heelstrike until footflat, causing obligatory internal tibial rotation (26, 27). External rotation of the tibia, femur and pelvis normally occurs from the beginning of stance phase until the beginning of the swing phase. Excessive pronation may prolong internal rotation of the tibia into stance phase until supination and hindfoot eversion begin as the foot begins to push off. This relative internal rotation is translated up the lower extremity and causes internal femoral rotation that effectively forces the lateral portion of the trochlea anteromedially against the lateral patellar facet during weightbearing. If pronation continues through the footflat phase and if the involved extremity pronates more than the patient's "normal" contralateral leg, the examiner should be suspicious that pronation is excessive and potentially aggravating to patellofemoral function. Prescription orthotics or shoes with good arch support and hindfoot control may help control tibial rotation and patellofemoral forces and facilitate rehabilitation (28, 29).
Squatting. Ask the patient to squat, and observe the mechanics and ease of squatting. The ease with which the patient can squat and rise to a standing position gives the examiner instant information regarding the severity of the condition. Correlate the intensity of patient complaints with observations of this simple provocative activity. If the patient can do this without using manual support, evaluation of dynamic closed chain patellar tracking is possible. Occasionally, one will observe a sudden medial shift of the patella as it enters the trochlea in early flexion. This finding is a positive J‑sign, so‑named because the patellar path resembles that of an upside down J. This indicates abnormal lateral tracking in early flexion secondary to multiple factors including relative VMO weakness and/or lateral retinacular tightness in most cases.
SEATED ALIGNMENT EXAMINATION
Tubercle Sulcus Angle. The patient sits on the edge of the examination table. Measure the 90‑degree tubercle sulcus angle by observing the position of the tibial tubercle relative to the center of the patella (Fig. 3.5).
When the knee is flexed to 90 degrees, the patella is generally captured within the trochlea. Measurement of this angle is therefore a reflection of lateral displacement of the tubercle with reference to the femoral sulcus. Hughston considered the normal 90‑degree tubercle sulcus angle to be 0 degrees (30). Kolowich et al consider that the upper limit of normal is 10 degrees lateral displacement, although data has not been presented to substantiate this range. (31). Compared with analysis of tubercle position by measurement of the Q angle, observation of lateral displacement of the tubercle relative to the patella in flexion more accurately portrays lateralization of the tubercle relative to the trochlea. Although the normal population values for the tubercle sulcus angle have not been well defined, lateralization of the tibial tubercle correlates with anterior knee pain (32), and examination of this relationship is helpful in understanding the contribution of tubercle position to the valgus alignment of the extremity.
Passive Patellar Tracking. Passively extend each knee watching patellar tracking and considering any difference with previously observed dynamic tracking.
Observation of tracking without quadriceps contraction allows the examiner to understand the contribution of the passive restraints (lateral retinaculum, ITB [iliotibial band], medial patellofemoral ligaments) to observed alignment. Observe particularly the entrance of the patella into the trochlea. The patella normally enters the trochlea by approximately 10 degrees of flexion. It should enter the trochlea smoothly without catches or sudden shifts. The J sign, which occurs when the patella shifts suddenly medially to enter the trochlea, is observed more often in passive tracking when the VMO is not actively guiding the patella into the trochlea. Comparison with the contralateral side is important.
SUPINE PATELLAR MOBILITY
Patellar Tilt Test. Test the patella for resistance to correction of lateral patellar tilt (rotation) by pushing posteriorly on the medial border of the patella while palpating the lateral margin of the patella to assess whether or not the patella corrects to at least neutral (Fig. 3.6). If the patellar tilt does not correct to neutral (parallel to the table) or beyond, one should be suspicious that mobility is significantly restricted. Patellar tilt test should be done in full extension with the quadriceps relaxed because this allows evaluation of the lateral soft‑tissue restraints in their most relaxed position. As with other supine tests for patellar mobility, walk around the table to examine the patient's opposite knee.
The lateral retinaculum includes contributions from the lateral patellofemoral and patellotibial ligaments and the iliotibial band (33). The iliotibial band is drawn posteriorly as the knee flexes, causing tension to increase in the iliopatellar band, the portion of the iliotibial band that inserts into the lateral retinaculum (34). Patellar mobility tests should therefore be done in full extension because it is in this position that there is normally the greatest mobility.
Lateral retinacular tightness is very common in patients with patellofemoral pain and is the hallmark of excessive lateral pressure syndrome as described by Ficat and Hungerford (35). The direction of the lateral retinaculum is posterior and lateral, but primarily posterior. Because the vector of the lateral retinaculum is principally posterior, excessive tension produces relatively more tilt (lateral rotation) than subluxation (lateral translation). Excessive tension can produce pain from soft‑tissue overload or secondarily from lateral patellar facet overload. The examiner should expect to be able to correct patellar tilt to neutral, but contralateral comparison is important because normal population data are lacking. Limited lateral retinacular flexibility is a very important finding and, if present, nonoperative treatment must include stretching of tight structures.
Medial‑Lateral Glide Test. Medial to lateral mobility should be tested by judging the amount of translation in each direction when firm pressure is applied (Fig. 3.7). Be careful to keep the patellar tilt constant during medial‑lateral glide testing. Watch for evidence of apprehension during medial‑lateral translation. If the patella is pushed medially and tilt is not controlled, the patella rotates externally. The examiner gets the false impression that the patella is displacing medially when much of the perceived displacement is rotational.
Static and dynamic factors affect patellar alignment. Normal tracking is the result of balance in the static peripatellar soft‑tissue restraints and good dynamic quadriceps strength and coordination. Medial‑lateral glide testing is useful to assess the static aspect of patellar alignment. Anatomically, Conlan et al showed that the medial patellofemoral ligament is the major static restraint to lateral displacement at full extension, conferring 53% of the medial restraining force (36). Although the amount of restraining force due to the medial patellofemoral ligament was somewhat variable (23‑80%), when it was anatomically distinct it was the primary medial restraint. The second most important medial static restraint was the medial patellomeniscal ligament that contributed 22% of restraining force. This laboratory data correlates well with the clinical findings of Sallay et al who noted that 15 of 16 patients who had undergone surgical exploration had tears of the medial patellofemoral ligament from the adductor tubercle after acute dislocation (37). Thus, when increased unilateral lateral translation is observed in full extension, the deficient tissues likely include the medial patellofemoral and patellomeniscal ligaments.
Medial‑lateral glide testing has been described in full extension (18, 38) and also with the knee in 30 degrees of flexion (16, 39). When this test is done in full extension it is more purely a test of peripatellar soft‑tissue compliance because there is less resistance from engagement of the patella in the trochlea. Estimation of the amount of translation may be accomplished by dividing the patella into longitudinal quadrants and estimating the degree of number of quadrants worth of translation that can be induced on examination. Kolowich et al measured mobility in 20 to 30 degrees of flexion and suggested that three quadrants of lateral glide suggested an incompetent medial restraint (31). Conversely, their opinion regarding medial glide was that one quadrant or less indicated an abnormally tight lateral retinaculum, whereas medial glide of three to four quadrants implied hypermobility.
Actual measurement of patellar mobility may become a welcome addition to patellofemoral examination because intertester reliability of more subjective evaluation has been shown to be poor among experienced physical therapists (40). Fithian et al reported patellar mobility measurements were reproducible between examiners and between repeated examinations by the same person (16). They suggested patellar "balance" be analyzed by calculating the difference between measured medial and lateral translations. Using this calculation, they found a difference between asymptomatic knees and knees with a history of patellar dislocation. As might be expected, contralateral knees of the instability patients were abnormal compared with asymptomatic controls but more normal than knees that had symptomatic instability. Skalley et al measured medial translation in full extension and found average translations to be 9.5 mm medially and 5.4 mm laterally (39). Standard deviations were not given, but the ranges cited for each direction were large (4‑15 mm) and again emphasize the importance of searching for contralateral asymmetry.
The apprehension sign occurs when the patient recognizes the sensation of impending dislocation during lateral glide testing. It is important to differentiate between pain and impending instability symptoms during the apprehension test. If the patient is truly apprehensive because of perceived instability, this strongly suggests that lateral patellar instability is an important part of that patient's diagnosis.
Special tests for medial subluxation Although lateral instability is much more commonly encountered, medial instability should be suspected if medial glide testing duplicates symptoms in a patient with a history of patellar realignment surgery. This can be considered a "reverse" apprehension test. In fact, physical examination is the primary method for diagnosis of medial subluxation (41‑44). Fulkerson's relocation test for symptomatic medial subluxation involves holding the symptomatic patella medially with the patient supine and the knee extended. Upon active or passive knee flexion, the patella falls into the trochlea and, when positive, reproduces the patient's pain or feeling of instability. The gravity subluxation test, as described by Nonweiler and DeLee (44), can also be helpful to confirm medial instability. They reported five symptomatic hypermobile patients in whom the vastus lateralis had been transected at the time of lateral release. When the patella is subluxed medially by the examiner with the patient in the lateral decubitus position, none of these patients could actively reduce their patella. Because medial subluxation occurs rarely, the gravity subluxation test need not be performed on all patients unless clinical suspicion exists for medial subluxation.
Superior‑Inferior Glide Test. Test superior and inferior patellar mobility in full extension by passive displacement of the patella (Fig. 3.8). Compare with the contralateral knee. Correlate with radiographic findings.
Decreased superior glide is a hallmark of infrapatellar contracture syndrome. This syndrome can result in debilitating anterior knee pain in the aftermath of knee surgery or blunt trauma. In florid cases, a knee flexion contracture is present, and the peripatellar soft tissues, including the infrapatellar fat pad, become fibrosed and firm. In less advanced cases, decreased superior glide may be one of the first signs of a developing infrapatellar contracture syndrome. If diagnosed promptly, this problem can be treated by physical therapy, particularly gentle persistent mobilization of the patella and peripatellar tissues. Surgical treatment of advanced cases can be difficult and results are not uniformly good (45).
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