Lateral Patellar Displacement Research Articles

The association of infrapatellar fat pad oedema with patellar maltracking: a case–control study

To look for any association between oedema in the superolateral portion of the infrapatellar fat pad and patellar maltracking. We compared two groups of knee MRI with regard to five patellar maltracking parameters. The first group included 100 knees with evidence of oedema in the superolateral aspect of the infrapatellar fat pad (the study group). The second group included another 100 knee MRI that had a normal infrapatellar fat pad (the control group). The five patellar maltracking parameters assessed were the trochlear depth, tibial tuberosity-trochlear groove distance (TTTG), patellar translation, patellofemoral angle (PFA) and the Insall-Salvati index. There was a statistically significant difference in the Insall-Salvati index, patellar translation and PFA between the two groups (p value of <0.001, <0.001 and 0.004 respectively, Student's t test). There was a higher prevalence of patella alta, lateral patellar displacement (LPD) and lateral patellar tilt in the study group (p value of <0.001, <0.001 and 0.011 respectively, Fisher's exact test). Sixty out of 100 knees in the study group had at least one abnormal patellar maltracking parameter in comparison to 16 out of 100 knees in the control group (p < 0.001, Fisher's exact test). Oedema in the superolateral portion of Hoffa's fat pad, the MRI feature of fat pad impingement, is associated with patellar maltracking.

Knee joint anterior malalignment and patellofemoral osteoarthritis: an MRI study

To evaluate patellofemoral congruency measurements on MRI and correlate the findings with severity of ipsilateral osteoarthritis. We retrospectively reviewed 650 consecutive knee MRI examinations from 622 patients divided into two age groups: ≤50 and >50 year-old. The femoral sulcus angle (SA) and depth (SD), lateral patellar displacement (LPD), lateral patellofemoral angle (LPFA), tibial tubercle-trochlear groove (TT-TG) distance and Insall-Salvati index as well as the grade of focal cartilage defects (ranging from I to IV) in the patellofemoral region were assessed in each subject on axial and sagittal fat-saturated intermediate-w MR images. A significant difference exists between normal and knees with patellofemoral joint osteoarthritis regarding SA (p = 0.0002 and <0.0001), SD (p = 0.0004 and <0.0001), LPD (p = 0.0014 and 0.0009) and LPFA (p = 0.0002 and 0.0003) in both age groups (≤50 and >50 respectively). Significant correlation was found between grading of cartilage defects and SA (rho = 0.21, p = 0.0001 and 0.443, <0.0001), SD (rho = -0.198, p = 0.0003 and -0.418, <0.0001), LPD (rho = 0.176, p = 0.0013 and 0.251, 0.0002) and LPFA (rho = -0.204, p = 0.0002 and -0.239, 0.0005) in both age groups. Knee joint anterior malalignment is multivariably associated with patellofemoral osteoarthritis. • MRI is an excellent method to evaluate knee alignment and articular cartilage damage. • Significant associations exist between alignment parameters and osteoarthritis of the patellofemoral joint. • The "sulcus angle" and "sulcus depth" were the most valuable osteoarthritic markers.

Patellar Fracture After Medial Patellofemoral Ligament Surgery

The medial patellofemoral ligament (MPFL) has been identified as the primary medial restraint to prevent lateral patellar displacement; it contributes up to 80% of the medial restraining forces on the patella1,2. Anatomically, the MPFL originates from the superior two-thirds of the medial patellar border and runs posteriorly toward the medial femoral epicondyle to insert in close relation to the origin of the superficial medial collateral ligament and slightly distal to the adductor tubercle3-5. Several techniques of MPFL repair and reconstruction have been described, with various graft options, tunnel placements, and fixation options, with or without concomitant procedures such as lateral retinacular release or tibial tuberosity osteotomy. Most techniques for patellar attachment of a reconstructed MPFL use patellar tunnels6-8, while some use suture anchors or soft-tissue fixation7,9,10. The potential complications of MPFL surgery include iatrogenic medial instability, persistent or recurrent lateral instability, patellofemoral arthrosis, loss of knee motion, and patellar fracture. In 1992, in a series of thirty patients, Ellera Gomes11 reported the first patellar fracture after MPFL reconstruction with use of a transverse patellar tunnel that traversed the entire width of the patella. Since then, eight patellar fractures have been reported after MPFL reconstruction with use of patellar bone tunnels. Four fractures in three series7,12,13 were attributed to technical errors associated with patellar tunnel placement. The other four fractures14,15 were medial rim avulsion fractures of the patella after MPFL reconstruction as the treatment for recurrent patellar dislocation. Fractures of the superior pole of the patella (superior pole sleeve avulsions) have been reported after medial soft-tissue imbrication and lateral retinacular release16-18; to our knowledge, similar proximal patellar fractures have not …

Patellar Subluxation at Terminal Knee Extension: Isolated Deficiency of the Medial Patellomeniscal Ligament

The medial patellomeniscal ligament has been determined in vitro to be the only substantial distal-medial restraint to lateral patellar displacement. The purpose of this study of prospectively collected data was to determine if isolated deficiency of the medial patellomeniscal ligament, resulting in excessive lateral patellar translation and associated symptoms, could be identified. We hypothesized that, if symptoms were associated with isolated deficiency of that ligament, the laxity and symptoms should resolve after plication of that ligament alone. Testing for lateral patellar displacement in the extended knee by exertion of force through the distal patellar attachment of the medial patellomeniscal ligament was performed on 745 patients with patellofemoral syndromes during a twenty-eight-month period. In addition, the ability to recognize pathologically increased lateral patellar translation preoperatively with use of such testing was compared with the ability to recognize increased lateral translation with testing in 439 patients undergoing arthroscopy under anesthesia during that period for any reason. Preoperative symptoms and impairment in knees with isolated deficiency of the medial patellomeniscal ligament were documented and compared with the postoperative results. Isolated medial patellomeniscal ligament deficiency was identified with testing under anesthesia in twenty-three of the 439 knees undergoing arthroscopy for any reason, and twenty of those twenty-three cases had been detected preoperatively with use of lateral patellar displacement testing. Isolated medial patellomeniscal ligament plication was performed in these twenty-three cases, and follow-up data at a mean of 30.8 months were available for twenty-one of the cases. The mean International Knee Documentation Committee subjective score increased from 38.9 preoperatively to 84.6 postoperatively, and recurrent symptomatic pathological lateral patellar translation was present in only one patient. Isolated deficiency of the medial patellomeniscal ligament can be detected by physical examination. Restoration of the normal length of the ligament by plication can lead to resolution of detectable patellar subluxation and its associated symptoms.

Femoral component rotation after balanced gap total knee replacement is not a predictor for postoperative patella position

Femoral component rotation is believed to be one of the factors influencing patellar tracking behavior. With the balanced gap implantation technique, the rotation of the femoral component can vary as it is guided by the ligaments. This study investigated whether femoral component rotation influenced patella position after primary total knee replacement (TKR). In this prospective cohort study, a primary TKR was implanted in 49 patients using a balanced gap technique and a CT-free navigation system. Femoral component rotation was measured using the navigation data of the distal femur cut, referenced from the posterior condyles. At the 2-year follow-up, lateral patellar tilt and patellar displacement were measured on axial patella radiographs. Logistic regression analysis on femoral component rotation and preoperative patella position was conducted to identify predictors for postoperative patellar tilt and displacement. Femoral component rotation that varied between -3 and 12° exorotation was not a predictor for postoperative tilt and displacement. Only preoperative displacement significantly predicted patella displacement. Although the balanced gap implantation technique resulted in a wide inter-patient variability for femoral component rotation, this variable rotation was not found to be associated with abnormal patellar position. Preoperative displacement results in a higher risk at a postoperatively displaced patella. The balanced gap technique can safely be used without an elevated risk for patella malposition.

Secondary patellar resurfacing in the treatment of patellofemoral pain after total knee arthroplasty

This paper reports a prospective review of patients who, between 2004 and 2007, underwent secondary patellar resurfacing (SPR) due to anterior knee pain after a primary total knee arthroplasty (TKA). The aim was to evaluate the clinical outcomes obtained with the SPR and to compare them with radiological findings. A total of twenty-seven consecutive patients met the inclusion criteria. There were twenty-three (85%) women and four (15%) men with a median age of 70 years. The patients were evaluated before and after the surgery with the same functional scores and radiological parameters. Bone scintigraphy was also used in the assessment, and a CT-scan was performed in order to evaluate the femoral component rotation. The median time between TKA and SPR was 18 months. With a median follow-up of 23 months, seventeen patients (63%) reported a clear subjective improvement after SPR, and patellofemoral scores (primary outcome measure), KSS and WOMAC (secondary outcome measures) showed a statistically significant improvement following the procedure. There were no significant changes after SPR in the Insall-Salvati ratio, the lateral patellar displacement or the lateral patellar tilt. The mean time between TKA and SPR had no statistically significant effect on outcome. The bone scintigraphy revealed increased patellar uptake in seven cases, but this was not related to subsequent improvement after SPR. Rotational computed tomography showed a median internal rotation of the femoral component of 1º. The complications observed were a patellar component loosening and an acute post-infection. No clinical or radiological parameter was found to be related to the final outcome after SPR. There was a discrepancy between functional scale scores and the patient's subjective satisfaction.

Immediate Effect and Predictors of Effectiveness of Taping for Patellofemoral Pain Syndrome

Background: Taping has been used to treat patellofemoral pain syndrome for more than 20 years, but its effectiveness is still controversial. Purpose: This study was undertaken to investigate the effect and predictors of effectiveness of taping in the treatment of patellofemoral pain syndrome. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 118 consecutive patients with patellofemoral pain syndrome were recruited; 100 of them completed this study. Patient sex, age, body mass index, Q angle, lateral patellar displacement, and lateral patellofemoral angle were recorded/measured. One therapist applied adhesive tape to each patient by the McConnell method. Patients scored their pain level on a 100-mm visual analog scale during stepping down from an 8-in platform, before and after taping. The change of score was evaluated by paired t test. Patients with a visual analog scale score decrease of 20 mm or more after taping were considered responsive, and the others were considered nonresponsive. The influences of the aforementioned factors, plus pretaping visual analog scale score, on the effectiveness of taping were analyzed by multivariate logistic regression. Results: The overall mean visual analog scale score decreased significantly after taping (from 49.0 to 29.3 mm; P < .001). There were 66 patients in the responsive group and 34 in nonresponsive group. Among the factors, body mass index, lateral patellofemoral angle, and Q angle were significant predictors of effectiveness. The responsive group had significantly smaller mean lateral patellofemoral angle, larger mean Q angle, and larger mean pretaping visual analog scale score than the nonresponsive group. Conclusion: Taping was an effective treatment for patellofemoral pain syndrome, but was less effective in patients with higher body mass index, larger lateral patellofemoral angle, and smaller Q angle.

The reliability and validity of radiological assessment for patellar instability. A systematic review and meta-analysis

To determine the discriminative validity and reliability of the evidence base using meta-analysis. A review of published sources using the databases AMED, CINHAL, EMBASE, MEDLINE, Scopus and the Cochrane Library, and for unpublished material was conducted. All studies assessing the reliability, validity, sensitivity or specificity of magnetic resonance imaging (MRI), computed tomography (CT) or ultrasound (US) of the patellofemoral joint of patients following patellar dislocation, subluxation or instability, were included. A meta-analysis was performed to assess the difference in radiological measurements between healthy controls and subjects with patellar instability in order to assess discrimination validity. A narrative assessment was used to evaluate the inter- and intra-observer reliability as well as the sensitivity and specificity of specific radiological measurements. A total of 27 studies were reviewed. The findings indicated that there was acceptable inter-observer and intra-observer reliability and validity for different methods of assessing patellar height and the sulcus angle with X-ray, MRI and CT methods, and the tibial tubercle-trochlear groove (TT-TG) assessed using CT. There was poor reliability or validity for the assessment of severity of trochlear dysplasia and the sulcus angle using US. There is insufficient evidence to determine the reliability, validity, sensitivity or specificity of tests such as the congruence angle, lateral patellar displacement, lateral patellar tilt, trochlear depth, boss height, the crossing sign or Wiberg patellar classification. A critical appraisal of the literature identified a number of recurrent methodological limitations. Further study is recommended to evaluate the reliability and validity of these radiological outcomes using well-designed radiological trials.

Femur Rotation and Patellofemoral Joint Kinematics: A Weight-Bearing Magnetic Resonance Imaging Analysis

Controlled laboratory study using a cross-sectional design. To compare patellofemoral joint kinematics, femoral rotation, and patella rotation between females with patellofemoral pain (PFP) and pain-free controls using weight-bearing kinematic magnetic resonance imaging. Recently, it has been recognized that patellofemoral malalignment may be the result of femoral motion as opposed to patella motion. Fifteen females with PFP and 15 pain-free females between the ages of 18 and 45 years participated in this study. Kinematic imaging of the patellofemoral joint was performed using a vertically open magnetic resonance imaging system. Axial-oblique images were obtained using a fast gradient-echo pulse sequence. Images were acquired at a rate of 1 image per second while subjects performed a single-limb squat. Measures of femur and patella rotation (relative to the image field of view), lateral patella tilt, and lateral patella displacement were made from images obtained at 45 degrees , 30 degrees , 15 degrees , and 0 degrees of knee flexion. Group differences were assessed using a mixed-model analysis of variance with repeated measures. When compared to the control group, females with PFP demonstrated significantly greater lateral patella displacement at all angles evaluated and significantly greater lateral patella tilt at 30 degrees , 15 degrees , and 0 degrees of knee flexion. Similarly, greater medial femoral rotation was observed in the PFP group at 45 degrees , 15 degrees , and 0 degrees of knee flexion when compared to the control group. No group differences in patella rotation were found. Altered patellofemoral joint kinematics in females with PFP appears to be related to excessive medial femoral rotation, as opposed to lateral patella rotation. Our results suggest that the control of femur rotation may be important in restoring normal patellofemoral joint kinematics. J Orthop Sports Phys Ther 2010;40(5):277-285, Epub 12 March 2010. doi:10.2519/jospt.2010.3215.

Indications in the treatment of patellar instability.

Recent developments in patellar instability have focused on the passive restraints against mediolateral patellar motion. Viewed from this perspective, muscle alignment is considered secondary because, although muscle forces are important, their ability to cause or prevent patellar dislocation depends on passive stability or the lack thereof. In the normal knee, the patella seats quickly in the trochlea in early flexion, so that the ligamentous restraints are important only near full extension. In the unstable patellofemoral joint, the trochlea frequently is deficient and patella alta often exists. In such cases, the ligaments assume a greater role in preventing excessive lateral patellar displacement. The most pressing questions at the moment are: 1) which of the anatomical abnormalities must be corrected, alone or in combination, to prevent further patellar instability; and 2) what is the relative risk of corrective procedures compared to the natural history or competing surgical approaches? These questions must be addressed by clinical trials. Only a minority of patients who experience patellar dislocation will redislocate the patella, and surgical treatment does not always yield results that are superior to conservative care. Treatment recommendations should be based on an individual's risk of recurrent dislocation, pain, and disability, a thorough understanding of his or her anatomy, and clear treatment objectives. Lateral release has no role in the treatment of a hyperlax patellofemoral joint, as it adds additional laxity to a system that is already unstable. If surgery is performed, current evidence suggests techniques aimed at repair or reconstruction of the passive retinacular restraints are as effective as more extensive procedures at preventing subsequent dislocations. Among the latter procedures, realignment procedures use active muscle forces to help seat the patella in the femoral groove; however, biomechanical costs are associated with this approach and superior results have not been demonstrated with distal and combined realignments compared with more limited proximal procedures.

Reconstruction of the medial patellofemoral ligament using a longitudinal patellar tunnel technique

Patellar instability is a common clinical problem affecting a young, active population. A large number of procedures have been described to treat patellar instability. We present the clinical results in a case series of 25 medial patellofemoral ligament reconstructions in 21 patients with up to 30 months follow-up (mean: 7.3). Reconstruction was performed using either the gracilis or semitendinosus tendon autograft. The Tegner activity score improved overall from 3 to 4.4 at follow-up and the mean follow-up Kujala score was 87 (range: 55-100). No patella redislocations were observed. Five patients (20%) required a manipulation under anaesthetic but subsequently regained a satisfactory range of motion. Medial patellofemoral reconstruction with both gracilis and semitendinosus tendon graft using a longitudinal tunnel technique provided good post-operative stability restoring the primary soft tissue restraint to pathological lateral patellar displacement with no complications of post-operative patellar fracture.

Anatomical double-bundle MPFL reconstruction with an aperture fixation

Since biomechanical studies have shown that the medial patellofemoral ligament (MPFL) is the main restraint against lateral patella displacement, reconstruction of the MPFL has become an accepted method of restoring patellofemoral stability and numerous techniques were described. Due to biomechanical examinations and clinical results, an anatomical double-bundle reconstruction of the "sail-like" MPFL is a reasonable method for achieving stability during complete extension and lower flexion degree. This method also serves to avoid rotation of the patella, providing immediate stability throughout the normal range of motion. However, until today, an aperture fixation technique at the patellar insertion with two bundles has not been described previously. This technique can provide an immediate stability to allow an early rehabilitation with full range of motion.

Correlating Anatomy and Congruence of the Patellofemoral Joint With Cartilage Lesions

Cartilage lesion of the patellofemoral joint is a common and challenging disease of the knee and an important cause of anterior knee pain. There are many naturally occurring variations in the anatomy and congruence of the patella and femoral trochlea. The purpose of this study was to identify the variations in patellofemoral anatomy and congruency that predispose to cartilage lesions. Among patients who underwent knee arthroscopy in our center from January 2005 to December 2006, 111 patients with chronic patellofemoral cartilage lesions and anterior knee pain were selected as the lesion group, while 124 patients with isolated meniscus rupture without anterior knee pain were selected as the control group. Twenty-one parameters measured on magnetic resonance images were used to assess the patellofemoral anatomy and congruence. A binary logistic regression model was used to look for possible associations between each of these parameters and the occurrence of patellofemoral cartilage lesions. The Bonferroni correction with a type I error rate of 0.0024 (0.05/21) was adopted to indicate statistical significance. Based on examination of the patellofemoral anatomy, 4 parameters were significantly associated with patellofemoral cartilage lesions. These were the patella lateral facet width, patella lateral facet ratio, sulcus depth and sulcus relative depth (P for linear trend <.0024). For patellofemoral congruence, 3 parameters were significantly associated with patellofemoral cartilage lesions. These were the lateral patella displacement, patella epicondylar axis angle and congruence angle (P for linear trend <.0024). Among the many kinds of patellofemoral variations, several were found to correlate with the development of patellofemoral cartilage lesions. These problems could be important risk factors for patellofemoral cartilage lesions.

The effect of knee flexion during tourniquet inflation, fat pad excision and lateral tibial release on patellar subluxation during MIS TKA

We compared the distance of patellar subluxation (lateral patellar displacement) during MIS TKA arthrotomy among sequential variations of tourniquet application and soft tissue release in a consecutive series of 40 knees. The distance of patellar subluxation from the Whiteside's line was measured for every knee under four consecutive conditions; A) the tourniquet inflated with knee in full extension, B) no tourniquet pressure applied, C) the tourniquet inflated with knee in deep flexion, and D) the tourniquet inflated with knee in deep flexion and lateral tibial release (a limited subperiosteal soft tissue dissection including limited patellar fat pad excision and limited capsular release from the upper lateral tibial plateau). There were 28 women and 12 men with the average age of 70 years and the average BMI of 25.5. All knees had preoperative flexion more than 110°. The tourniquet pressure ranged from 280 to 300 mm Hg. The average skin incision length was 9 cm. The average measured distance of condition A, B, C and D were 10, 14.5, 15.8 and 22 mm, respectively with significant difference ( p < 0.001). The distance of patellar subluxation correlated between conditions A) and C) ( r 2, 0.67) and between conditions C) and D) ( r 2, 0.72) in the studied group. However, there was no statistical difference of measured distance between group with condition B and C ( p = 0.40). In conclusion, when MIS TKA is performed using the tourniquet, inflating the tourniquet with knee in deep flexion provided better arthrotomy exposure than the knee in full extension. Combined inflating tourniquet in deep knee flexion and lateral tibial release provided the greatest arthrotomy visualization.

Anatomical reconstruction of the medial patellofemoral ligament using a free gracilis autograft

Since biomechanical studies have shown that the medial patellofemoral ligament (MPFL) is the main restraint against lateral patella displacement, reconstruction of the MPFL has become an accepted surgical technique to restore patellofemoral stability. Recently, various procedures have been described that address reconstruction of the medial patellofemoral complex. We present a technique, where the MPFL is reconstructed anatomically to restore physiological kinematics and stability, using a free gracilis tendon autograft.

The Medial Patellofemoral Ligament

There has been substantial progress in our understanding of the medial patellofemoral ligament during the past 10 years. This structure is the primary static soft-tissue restraint to lateral patellar displacement. Substantial alteration of normal patellar tracking occurs after sectioning of the ligament. Clinical studies have demonstrated the medial patellofemoral ligament is disrupted during acute patellar dislocation. Recently, several medial patellofemoral ligament-based procedures have been developed for the treatment of patellar instability with good early results. However, further studies are needed to define the exact role of these procedures in the treatment of patellofemoral instability.

Comparison of Patellar Mobility in Female Adults With and Without Patellofemoral Pain

Case control study. To compare the patellar mobility of female adult subjects with and without patellofemoral pain (PFP). Although abnormal patellar mobility is believed to be one of the causes of PFP, there is currently no published evidence to support this contention. In part, this lack of evidence is because a reliable clinical measurement method to measure patellar mobility and objective criteria to define abnormal patellar mobility have not been established. The study sample was comprised of 22 females with PFP (PFP group) and 22 females who had no knee pain (control group), matched by age, height, and body mass index to the subjects with PFP. Patellar mobility was measured objectively using a specially designed apparatus. Measurements of lateral and medial patellar displacement, patellar mobility balance (lateral minus medial patellar displacement), lateral patellar mobility index (lateral patellar displacement divided by patellar width), and medial patellar mobility index (medial patellar displacement divided by patellar width) were used. Lateral and medial patellar mobility values were not significantly different between the individuals in the PFP and control groups. When normal patellar mobility was arbitrarily defined as the average mobility +/- 2 SDs, based on the data from the control group, normal lateral patellar displacement was within a range of 7.2 to 17.6 mm and normal medial patellar displacement was within a range of 6.8 to 14.0 mm. The intraclass correlation coefficient for intratester and intertester reliability of lateral and medial patellar displacement measurements varied from 0.80 to 0.97. Although there were no significant differences in patellar mobility between females with and without PFP, these measurements give reference information about normal patellar mobility for this group. Diagnosis, level 5.

In vivo patellar tracking: Clinical motions and patellofemoral indices

Patellar tracking during in vivo weightbearing knee function is not well understood. This study investigated patellar tracking of eight subjects during a full range of weightbearing flexion using magnetic resonance imaging and dual orthogonal fluoroscopy. The data were reported using a clinical description based on patellar and femoral joint coordinate systems and using patellar indices based on geometrical features of the femur and patella. The mean patellar shift was within 3 mm over the entire range of flexion. The patella tilted laterally from 0 degrees to 75 degrees, and then tilted medially beyond 75 degrees of flexion. The mean tilt was within 6 degrees. Similarly, the mean patellar rotation was small at early flexion, and the mean total excursion of patellar rotation was about 8 degrees. The patellofemoral indices showed that the mean sulcus angle and congruence angle varied within 8 degrees over the entire flexion range. The mean lateral patellar displacement was within 6 mm. A consistent decrease in lateral patellar tilt and an increase in lateral patellofemoral angle were observed with knee flexion. In conclusion, patellar motion is relatively small with respect to the femur during in vivo weightbearing knee flexion. These data may provide baseline knowledge for understanding normal patellar tracking.

Relationship between the EMG ratio of muscle activation and bony structure in osteoarthritic knee patients with and without patellar malalignment

The aim of this study was to compare muscle activation patterns and patellofemoral joint morphologies between patients with knee osteoarthritis with and without patellar malalignment. The subjects were divided into 3 groups. Group A comprised 11 patients with symptomatic knee osteoarthritis without patellar malalignment. Group B comprised 14 patients with symptomatic knee osteoarthritis with patellar malalignment. Group C comprised 10 age-matched subjects with non-knee osteoarthritis as controls. Isokinetic dynamometry with surface electromyography was used to measure maximal muscle activity in terms of vastus medialis oblique/vastus lateralis ratios. Merchant's view was taken to analyse the bony anatomy of the patellofemoral joint. Recordings were made at angular velocities of 80, 120 and 240 masculine/sec. The electromyographic ratios of group B were lower than groups A and C for all testing velocities (p<0.05). Group B also had larger sulcus angles, lateral patellar tilt and displacement. The electromyographic ratios correlated negatively with sulcus angles. Subjects with knee osteoarthritis with patellar malalignment exhibited an imbalance in quadriceps contraction, as confirmed by altered vastus medialis oblique/vastus lateralis ratios associated with larger sulcus angles of the patellofemoral joints. The sulcus angle may be an important contributing factor in causing abnormal patellar tracking in knee osteoarthritis.

Patellofemoral Joint Contact Area Is Influenced by Tibiofemoral Rotation Alignment in Individuals Who Have Patellofemoral Pain

Observational, cohort study. To test the hypothesis that patellar alignment and tibiofemoral rotation alignment explain unique portions of variance in patellofemoral joint contact area in individuals with patellofemoral pain (PFP) and in pain-free control subjects. PFP has been proposed to result from increased patellofemoral joint stress due to decreased contact area. Patellar malalignment (lateral displacement and tilt) is believed to be the main contributor to decreased contact area. Recent studies suggest that transverse plane rotation of the femur and/or tibia may also contribute to decreased contact area. Twenty-one subjects with PFP (16 female, 5 male) and 21 pain-free subjects (14 female, 7 male) participated. Subjects underwent magnetic resonance imaging with the knee in full extension and the quadriceps contracted. Measures of patellofemoral joint contact area, lateral patellar displacement, patellar tilt angle, tibiofemoral rotation angle, and patellar width were obtained. Hierarchical multiple regression analyses were performed for each group using contact area as the dependent variable. The order of independent variables was patellar width, patellar tilt angle, and tibiofemoral rotation angle. To avoid multicolinearity, lateral patellar displacement was not included. In the PFP group, patellar width and tibiofemoral rotation angle explained 46% of the variance in contact area. In pain-free subjects, patellar width was the only predictor of contact area, explaining 31% of its variance. Patellar tilt angle did not predict contact area in either group. Addressing factors that control tibiofemoral rotation may be indicated to increase contact area and reduce pain in individuals with PFP. Future studies should investigate the contributions of patellar alignment and tibiofemoral rotation to patellofemoral joint contact area at a variety of knee flexion angles.