Patellar motion analyzed by magnetic resonance imaging

We have analyzed the normal patellar motion during the first 30° of knee flexion by magnetic resonance imaging (MRI). Ten males and 10 females without knee symptoms were examined. The patellar articulation was imaged both sagitally and axially with the knee flexed 0,10,20, and 30°. The axial images were produced through the middle of the patellar articular cartilage. When the knee was in extension compared to 30° flexion, the sulcus angle was greater, the lateral patellofemoral angle was smaller, there was more lateral patellar displacement, the patella tilted more laterally, and the congruence angle was directed more laterally. Differences between males and females were found.     

Patellar motion analyzed by magnetic resonance imaging

We have analyzed the normal patellar motion during the first 30 degrees of knee flexion by magnetic resonance imaging (MRI). Ten males and 10 females without knee symptoms were examined. The patellar articulation was imaged both sagittaly and axially with the knee flexed 0, 10, 20, and 30 degrees. The axial images were produced through the middle of the patellar articular cartilage. When the knee was in extension compared to 30 degrees flexion, the sulcus angle was greater, the lateral patellofemoral angle was smaller, there was more lateral patellar displacement, the patella tilted more laterally, and the congruence angle was directed more laterally. Differences between males and females were found.     

Axial computed tomography of the patellofemoral joint with and without quadriceps contraction

Computed tomography was used to analyze the patellofemoral relationship during the first 60° of knee flexion in patients with chronic patellofemoral pain syndrome (49 knees) and a healthy control group (15 knees). The patellofemoral joints were imaged axially through the center of the patella articular cartilage with the knee flexed 0°, 0° with maximal quadriceps muscle contraction, 30°, and 60°. In 0° of knee flexion, the sulcus angle was greater in the symptomatic group than in normal controls. The patella displaced further laterally, and the lateral patellar tilt was greater. The patellar lateral index was found to be greater at 0° and indicated severe abnormality with full quadriceps muscle contraction. The Laurin angle was pathologic with increased medial opening, especially with muscle contraction. At 30° of knee flexion, these differences were less marked than at 0°. No relevant differences were found with 60° of knee flexion. This study showed that the sulcus angle, lateral patellar displacement, lateral patellar tilt, patella lateral condyle index, and Laurin angle are relevant diagnostic features in 0° of knee flexion, indicating a pathological femoral patellar gliding mechanism. Our evaluation also demonstrated the influence of full quadriceps muscle contraction, especially regarding lateral patellar displacement and the Laurin angle, and it was most prominent on the patella lateral condyle index. Thus, quadriceps muscle contraction often creates a more pathological displacement of the patella, which can be depicted using axial computed tomography.     

髌股关节软骨与软骨下骨的几何学匹配性及临床意义

目的 测量并比较髌股关节软骨覆盖和软骨下骨的几何形状.方法 2009年1月至2010年3月,选取髌股关节正常的膝关节标本9例,在膝关节屈曲20°～30°位,沿髌骨中心垂直于髌股关节面横行切开,暴露髌股关节,测量骨性髌骨适合角、软骨性髌骨适合角、髌骨软骨顶点参数、髌骨软骨下骨顶点参数、滑车骨性凹点参数和滑车软骨凹点参数.然后在临床中随机选取11例髌股关节软骨覆盖及力线正常患者的髌股关节轴位MRI,测量上述指标,与解剖学研究进行比较.结果 解剖学样本数据:骨性髌骨适合角为(-4.5±1.1)°,软骨性髌骨适合角为(0.5±0.8)°,均为右膝;髌骨软骨顶点参数为1.13±0.11,髌骨软骨下骨顶点参数为1.67±0.14,滑车骨性凹点参数为1.35±0.28,滑车软骨凹点参数为1.38±0.33.骨性髌骨适合角与软骨性髌骨适合角差异有统计学意义(P＜0.05),髌骨软骨顶点参数与髌骨软骨下骨顶点参数差异有统计学意义(P＜0.05).滑车骨性凹点参数与滑车软骨凹点参数差异无统计学意义(P＞0.05).临床影像学样本数据和解剖学数据相近,差异无统计学意义(P＞0.05).结论 覆盖髌骨软骨的几何形状与软骨下骨的几何形状存在着明显的差异,而股骨滑车软骨与软骨下骨的几何形状基本相似.     

Patellofemoral relationships in recurrent patellar dislocation

Magnetic resonance imaging was used to analyse the patellofemoral relationships during the first 30 degrees of knee flexion in women with recurrent patellar dislocation. The patellofemoral joints were imaged both sagittally and axially with the knee flexed 0 degrees, 10 degrees, 20 degrees, and 30 degrees. At the beginning of knee flexion the sulcus angle was greater than in unaffected women, the lateral patellofemoral angle was smaller, the patella displaced further laterally, tilted more laterally and the congruence angle was directed more laterally. At 30 degrees of knee flexion these differences were less marked than at 0 degree to 10 degrees. Logistic regression analysis showed that the sulcus angle at 10 degrees of knee flexion was the most diagnostic feature, indicating that there is an anatomical predisposition to recurrent dislocation and that pathological patellar tracking starts from the beginning of flexion. Traditional sunrise radiographic films taken at 25 degrees to 30 degrees knee flexion clearly miss diagnostically important information.     

The influence of iliotibial tract on patellar tracking

Thirty patients with 49 snapping hips and patellar malalignment underwent surgical release of the iliotibial tract contracture over the trochanteric area. Minimal follow-up was 2 years (average 4.6 years, range: 2-9 years). Eight patients underwent computed tomography (CT) preoperatively and 1 month postoperatively to investigate the patellar location in the patellofemoral articulation with knee bending at 0 degrees, 20 degrees, 45 degrees, 60 degrees, and 90 degrees. Significant improvements in the congruence angle and lateral patellofemoral angle were noted on Merchant radiograph for all knees (P<.01). On CT, at 20 degrees and 45 degrees knee bending, all congruence, lateral patellofemoral, and patellar tilt angles significantly improved postoperatively in 8 knees (P<.01). Iliotibial tract affects patellar tracking and dominates lateral patellar supporting structures.     

Patellar angle in Osgood-Schlatter disease

A new patellar angle is described in lateral radiographs of the knee joint. One line is drawn along the articular surface of the patella and another from the end of the inferior articular cartilage to the patellar apex. The angle formed by these two lines averaged 33° in 68 knees joints afflicted with Osgood-Schlatter disease and 47° in 71 age-matched controls and 198 adult controls. The small angle in Osgood-Schlatter disease is proposed to be an important factor in the pathogenesis of the traction apophysitis.     

Shortening of the patellar tendon length does not influence the patellofemoral alignment in a cadaveric model

Introduction Anterior cruciate ligament (ACL) reconstruction with the use of autograft tissue represents the standard treatment. The use of a bone-patellar tendon-bone transplant for symptomatic ACL deficiency achieves good long-term results. The purpose of the study was to investigate in a cadaveric model whether reproducible patellar tendon shortening changes the patellofemoral alignment.Materials and methods Using five cadaveric knees, an MRI investigation was performed with the patellar tendon left unchanged, shortened 5 mm and shortened 10 mm, respectively, in both 20 and 45° of knee flexion. The lateral patellofemoral and the congruence angles were measured and compared using a one-way analysis of variance for repeated measurements.Results Shortening the patella tendon by approximately 20% did not significantly influence the patellofemoral alignment.Conclusion Although anterior cruciate ligament-reconstruction using the patellar tendon has become a standard procedure, postoperative problems such as anterior knee pain, and patellofemoral osteoarthritis occur quite often. In this cadaver study we did not find a significant difference for the patellofemoral alignment, irrespective of the patellar tendon length.     

Using real‐time MRI to quantify altered joint kinematics in subjects with patellofemoral pain and to evaluate the effects of a patellar brace or sleeve on joint motion

Abnormal patellofemoral joint motion is a possible cause of patellofemoral pain, and patellar braces are thought to alleviate pain by restoring normal joint kinematics. We evaluated whether females with patellofemoral pain exhibit abnormal patellofemoral joint kinematics during dynamic, weight‐bearing knee extension and assessed the effects of knee braces on patellofemoral motion. Real‐time magnetic resonance (MR) images of the patellofemoral joints of 36 female volunteers (13 pain‐free controls, 23 patellofemoral pain) were acquired during weight‐bearing knee extension. Pain subjects were also imaged while wearing a patellar‐stabilizing brace and a patellar sleeve. We measured axial‐plane kinematics from the images. Females with patellofemoral pain exhibited increased lateral translation of the patella for knee flexion angles between 0°and 50° (p = 0.03), and increased lateral tilt for knee flexion angles between 0° and 20° (p = 0.04). The brace and sleeve reduced the lateral translation of the patella; however, the brace reduced lateral displacement more than the sleeve (p = 0.006). The brace reduced patellar tilt near full extension (p = 0.001), while the sleeve had no effect on patellar tilt. Our results indicate that some subjects with patellofemoral pain exhibit abnormal weight‐bearing joint kinematics and that braces may be effective in reducing patellar maltracking in these subjects. Published by Wiley Periodicals, Inc. J Orthop Res 27: 571–577, 2009     

Patellar tracking and patellofemoral geometry in deep knee flexion.

Patellar tracking and femoral condylar geometry in deep knee flexion were evaluated using magnetic resonance imaging. The patellar tilting angle, patellar shift, and patellar anteroposterior translation from 0 degrees to 135 degrees flexion were measured. The depth of the femoral condylar articular surface and the curvature of the femoral condylar articular surface also were measured at 135 degrees flexion. The patella shifted laterally, tilted medially, and sank deeply into the intercondylar notch during deep knee flexion. The articular surface of the lateral condyle, existing deep within the intercondylar notch, began to curve steeply at a point farther from the center of the intercondylar notch than did the medial condyle. The geometry of the femoral condyle is adequate to fit the patellar geometry. Results of the current study suggest that the geometry of the lateral femoral condyle allows the patella to track smoothly with a larger patellofemoral contact area and less patellofemoral pressure during deep flexion.     

Patella alta: association with patellofemoral alignment and changes in contact area during weight-bearing

BACKGROUND: Patella alta is a condition which may predispose individuals to patellofemoral joint dysfunction. We compared patellofemoral joint alignment and contact area in subjects who had patella alta with subjects who had normal patellar position, to determine the effect of high vertical patellar positions on knee extensor mechanics. METHODS: Twelve subjects with patella alta and thirteen control subjects participated in the study. Lateral patellar displacement (subluxation), lateral tilt, and patellofemoral joint contact area were quantified from axial magnetic resonance images of the patellofemoral joint acquired at 0 degrees , 20 degrees , 40 degrees , and 60 degrees of knee flexion with the quadriceps contracted. RESULTS: With the knee at 0 degrees of flexion, the subjects with patella alta demonstrated significant differences compared with the control group, with greater lateral displacement (mean [and standard error], 85.4% +/- 3.6% and 71.3% +/- 3.0%, respectively, of patellar width lateral to the deepest point in the trochlear groove; p = 0.007), greater lateral tilt (mean, 21.6 degrees +/- 1.9 degrees and 15.5 degrees +/- 1.8 degrees ; p = 0.028), and less contact area (157.6 +/- 13.7 mm(2) and 198.8 +/- 14.3 mm(2); p = 0.040). Differences in displacement and tilt were not observed at greater knee flexion angles; however, contact area differences were observed at all angles evaluated. When data from both groups were combined, the vertical position of the patella was positively associated with lateral displacement and lateral tilt at 0 degrees of flexion and was negatively associated with contact area at all knee flexion angles. CONCLUSIONS: These data indicate that the vertical position of the patella is an important structural variable that is associated with patellofemoral malalignment and reduced contact area in patients with patella alta.     

Subluxation of the patella. Computed tomography analysis of patellofemoral congruence

Fifty patients who had patellar subluxation and thirty control subjects were examined using axial roentgenograms of the patellofemoral joint that were made with the knee in 30 and 45 degrees of flexion, as well as computed tomography scans that were made with the knee in full extension. The amount of lateral patellar tilt was quantitatively assessed using the lateral patellofemoral angle, as described by Laurin et al., and the congruence angle, as described by Merchant et al. In both the control subjects and the patients, the angle of Laurin et al. changed significantly when the knee was flexed from full extension to 30 degrees. The difference between the groups was statistically significant at each angle of flexion of the knee, and the difference between the groups was most prominent on the computed tomography scans that were made with the knee in full extension (p less than 0.001). In the patients, the average congruence angle (as described by Merchant et al.) was 5 degrees and in the control subjects, -10 degrees. This indicated that, in our patients, the extent of the patellar subluxation was less than that in previously reported series, and, as a result, the sensitivity of the congruence angle in diagnosing patellar subluxation was only 0.30. In contrast, the sensitivity and specificity of the computed tomography scans for diagnosing patellar subluxation were 0.96 and 0.90, respectively--that is, they were higher than the values that were obtained using any axial roentgenograms. Thus, our results indicated that patellar subluxation can be detected more accurately by using computed tomography with the knee in full extension than by using conventional axial roentgenograms.     

Patellar component positioning in total knee arthroplasty

Five human anatomic specimen knees were used to determine the effect of patellar component position on patellofemoral kinematics, contact pressures, and contact areas after total knee arthroplasty using a polyethylene, domed patellar component. Each patellar component was positioned at the anatomic center of the resected patellar surface and then repositioned 5 mm proximally, distally, medially, and laterally. Patellar tilt was greatest with medial positioning of the patellar component and least with central and lateral positioning. At higher knee flexion angles, patellofemoral joint contact pressures increased at the medial facet with the medialized component and at the lateral facet for the lateralized component. The centralized component had the most evenly balanced patellar facet contact pressures. Distally positioned patellar components resulted in decreased patellar component loading at higher knee flexion angles. Central positioning of the patellar component results in optimal patellofemoral mechanics when maximal coverage of the resected patella is desired.     

Effect of lateral release on patellar motion in chondromalacia: An MRI study of 11 knees

Preoperatively and postoperatively, patellar motion in 11 knees with chondromalacia was analyzed by MRI at 0°, 10°, 20°, and 30° of knee flexion. The preoperative patellar position clearly deviated from normal at 0°-10° of knee flexion. The lateral release operation corrected this deviation.     

A modified system of stress radiography for patellofemoral instability

Axial radiographs were obtained under valgus and external rotation stress at 45 degrees of knee flexion with and without contraction of the quadriceps muscle in order to assess the dynamics of patellar subluxation or dislocation. The radiography was performed on 82 knees in 61 patients with patellofemoral instability, and on 44 normal knees. The lateral patellofemoral angle and the congruence angle were measured and compared with the conventional Merchant views. Both parameters showed greater differences between symptomatic and normal knees on the stress radiographs obtained without quadriceps contraction. There was a major difference in the lateral patellofemoral angles between the groups, which clearly distinguished symptomatic knees from normal controls. Congruence angles on stress radiography had a significant correlation with the functional scores obtained after a period of conservative treatment and a positive correlation with the frequency of patellar subluxation. When the quadriceps contracted, two patterns of patellar shift were observed. While the patella reduced into the trochlear groove in all normal knees and about 70% of the symptomatic knees, contraction of the quadriceps caused further subluxation of the patella in the remaining symptomatic knees. All the knee joints which showed this displacement failed to respond to conservative treatment and eventually required surgical treatment. Thus, this technique of stress radiography is a simple, cost-effective and useful method of evaluating patellar instability and predicting the prognosis.     

基于筋束骨理论铍针松解髌骨外侧支持带改善髌股关节应力集中的有限元分析

目的:在筋束骨理论指导下,基于膝关节有限元模型研究铍针松解髌骨外侧支持带改善髌股关节应力集中的机制,阐释铍针松解术改变髌骨运行轨迹及降低髌股关节压力的生物力学机制.方法:获取 1 名正常男性(年龄29 岁,身高171 cm,体重58 kg)膝关节CT 资料,从膝关节的三维有限元模型构建入手,经几何重建、逆向工程、网格划...     

The association between patellofemoral alignment and osteoarthritis in magnetic resonance imaging

ObjectivesOsteoarthritis (OA) is the most common joint disease in the world, becoming more prevalent with increasing age, and causes a significant burden on individuals and society. So far, several factors have been identified in association with OA of the knee joint. Age is the most crucial uncontrollable risk factor for OA. There are conflicting results regarding the relationship between patellofemoral joint orientation and OA. This study aims to elucidate the relationship between patellofemoral joint alignment and OA evidence.Material and methodsA total of 277 MRIs performed at Imam Reza Hospital during the first half of 2017 were included. Patients were divided into two groups, under 50 years old and over 50 years old. Femoral sulcus angle (SA) and depth (SD), lateral patellar displacement (LPD), tibial tubercle-trochlear groove (TTTG), lateral patellofemoral angle (LPFA), and Insall-Salvati index were measured in axial and sagittal images. The morphology of the patellofemoral articular cartilage was evaluated and the grade of joint damage was determined. P-value < 0.05 was considered as significant.ResultsSignificant correlations between SA (p-value = 0.01), SD (p-value < 0.001), Insall-Salvati index (p-value < 0.001), LPD (p-value = 0.02) values and OA in patients less than 50 years old were observed. A weak correlation was observed between SD and Insall-Salvati index values with increasing grade of articular cartilage damage (r = 0.21 and r = 0.21, respectively).ConclusionsPatellofemoral joint asymmetry in the younger people was significantly associated with joint cartilage damage and premature patellofemoral joint OA. Joint misalignment by stressing the articular cartilage causes joint cartilage changes that may be congenital or due to bone injuries such as trauma and surgery.     

Quantitative measurement of patellofemoral joint stability: force-displacement behavior of the human patella in vitro.

Patellofemoral joint instability is a common clinical problem. However, little quantitative data are available describing the stability characteristics of this joint. We measured the stability of the patella against both lateral and medial displacements across a range of knee flexion angles while the quadriceps were loaded physiologically. For eight fresh-frozen knee specimens a materials testing machine was used to displace the patella 10 mm laterally and 10 mm medially while measuring the required force, with 175 N quadriceps tension. The patella was connected via a ball-bearing patellar mounting 10 mm deep to the anterior surface to allow natural tilt and other rotations. Patellar force-displacement behavior was tested at flexion angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees. Significant differences were found between the lateral and medial restraining forces at 10 mm displacement. For lateral displacement, the restraining force was least at 20 degrees of knee flexion (74 N at 10 mm displacement), rising to 125 N at 0 degrees and 90 degrees of knee flexion. The restraining force increased progressively with knee flexion for medial patellar displacement, from 147 N at 0 degrees to 238 N at 90 degrees. With quadriceps tension, the patella was more resistant to medial than lateral displacement. Our finding that lateral patellar displacement occurred at the lowest restraining force when the knee was flexed 20 degrees agrees with clinical experience of patellar instability.     

Injuries produced by blunt trauma to the human patellofemoral joint vary with flexion angle of the knee.

Patellofemoral joint impact trauma during car accidents, sporting activities, and falls can produce acute gross fracture of bone, microfracture of bone, and soft tissue injury. Field studies of car accidents, however, show that most patellofemoral traumas are classified as 'subfracture' level injuries. While experimental studies have shown that the influence of flexion angle at impact is not well understood, flexion angle may influence injury location and severity. In the current study, 18 pairs of isolated human cadaver knees were subjected to blunt impact at flexion angles of 60 degrees, 90 degrees, or 120 degrees. One knee from each cadaver was sequentially impacted until gross fracture of bone was produced. The contralateral knee was subjected to a single, subfracture impact at 45% of the impact energy producing fracture in the first knee. The fracture experiments produced gross fracture of the patella and femoral condyles with the fracture plane positioned largely within the region of patellofemoral contact. The fracture location and character changed with flexion angle: at higher flexion angles the proximal pole of the patella and the femoral condyles were more susceptible to injury. For the 90 degrees flexion angle, the patella was fractured centrally, while at 60 degrees the distal pole fractured transversely at the insertion of the patellar tendon. In addition, the load magnitude required to produce fracture increased with flexion angle. In the 'subfracture' knees, injuries were documented for all flexion angles; occult microfractures of the subchondral and trabecular bone and fissures of the articular surface. Similar to the fracture-level experiments, the injuries coincided with the patellofemoral contact region. These data show that knee flexion angle plays an important role in impact related knee trauma. Such data may be useful in the clinical setting, as well as in the design of injury prevention strategies.