Intra-articular knee injuries in patients with knee extensor mechanism ruptures

The knee extensor mechanism is composed of the quadriceps tendon, patella and patellar tendon. Rupture of either the quadriceps tendon or patella tendon is a rare but significant injury. The purpose of our study is to determine if there are any associated injuries with these ruptures necessitating the need for further evaluation such as MRI or arthroscopy. We retrospectively reviewed all patients with ruptures of the knee extensor mechanism who required operative repair at our institution over the last 10 years. We reviewed the chart for any documented associated injury. The type and incidence of associated injuries were recorded. We further divided these patients into two groups: low energy indirect mechanism or high-energy direct impact mechanism. Sixty-four patients met our requirements for inclusion in this study. Thirty-three patients with patellar tendon ruptures and thirty-one patients with quadriceps tendon ruptures were included. Ten out of 33 (30%) patients with a patellar tendon rupture had an associated injury. Four out of 25 (16%) patients with patellar tendon ruptures in the low energy mechanism category had an associated injury. Six out of 8 (75%) patients with a high-energy direct impact patellar tendon rupture had an associated injury. Three out of 31 (10%) patients with quadriceps tendon rupture had an associated injury. The most common associated injuries in the patellar tendon rupture patients were anterior cruciate ligament tears (18%) and medial meniscus tears (18%). We found almost one-third of all patients with a patellar tendon rupture had an associated intra-articular knee injury. We found 10% of patients with quadriceps tendon rupture had an associated intra-articular knee injury. We also found an even higher incidence of associated injuries in patients with high-energy direct impact mechanism patellar tendon ruptures (75%). The most common associated injuries in patients with patellar tendon ruptures were tears of the anterior cruciate ligament (18%) and medial meniscus (18%). We recommend that consideration be given in obtaining a MRI or diagnostic arthroscopy in patients with patellar tendon ruptures especially those with high-energy direct impact mechanism. To our knowledge this has not previously been documented in the literature.     

Evaluation of the quadriceps tendon, patellar tendon, and collateral ligaments after total knee arthroplasty: appearances in the early postoperative period.

OBJECTIVE: To evaluate and compare the normal appearance on ultrasound and magnetic resonance imaging (MRI) of the quadriceps tendon, patellar tendon, and collateral ligaments in the early postoperative period following total knee arthroplasty. METHODS: Within a 6-month period, 10 patients with a total knee arthroplasty were referred for imaging. All patients had surgery within 12 weeks, and both MRI and ultrasound were performed on the same day. Two experienced musculoskeletal radiologists, blind to the results of the opposing modality, assessed the integrity of the quadriceps tendon, patellar tendon, and collateral ligaments. RESULTS: Using ultrasound, we identified a focal defect within the medial aspect of the quadriceps tendon in 8 (80%) patients; a similar defect was detected in 5 (50%) patients on MRI. The patellar tendon was thickened in 10 (100%) patients in both modalities. The medial collateral ligament was visualized in 10 (100%) patients with ultrasound and was demonstrated in only 2 (20%) patients with MRI. The lateral collateral ligament was visualized in 7 (70%) and 4 (40%) patients with ultrasound and MRI, respectively. One moderately sized superficial hematoma was demonstrated on ultrasound but was missed on MRI. All abnormalities identified on MRI were also seen with ultrasound. CONCLUSION: A medial defect in the quadriceps tendon and thickened patellar tendon and medial collateral ligament can be considered normal findings. Knowledge of these findings will assist in preventing incorrect diagnosis of a tear. In our cases, ultrasound detected more findings than did MRI.     

髌骨与髌韧带长度比值的MR测量

目的:通过MR成像确定髌骨与髌韧带长度比值的正常范围,诊断髌骨位置异常。方法:无髌骨及髌韧带损伤患者311名,行单膝关节MRI检查。在MRI矢状面图像上测量髌骨长度(PL)和髌韧带长度(TL),并计算TL/PL的比值。比值分布范围的两个极端2.5%认为是髌骨高位和髌骨低位。结果:TL/PL值范围为0.617～1.88(平均1.067)。MRI上髌骨高位的TL/PL值>1.433,髌骨低位的TL/PL值<0.775。女性的TL/PL值(平均1.083)和男性(平均1.054)差异有显著性意义(P<0.05)。本研究人群与以色列学者Shabshin等所研究人群之间的TL/PL比值分布没有统计学差异(t=1.865,P=0.063>0.05)。结论:MRI上TL/PL值的正常范围为0.775～1.433(平均1.067)。>1.433可认为髌骨高位;<0.775可认为髌骨低位。通过MRI诊断髌骨高位和髌骨低位准确可行。     

Patellar tendon length after anterior cruciate ligament reconstruction: a comparative magnetic resonance imaging study between patellar and hamstring tendon autografts

Patellar tendon shortening after anterior cruciate ligament reconstruction may be associated with anterior knee pain or patellofemoral arthritis. The present study was designed to compare postoperative changes in patellar tendon length after anterior cruciate ligament reconstruction between patellar tendon and hamstring tendon autograft. Magnetic resonance images of both knees (operated and healthy) and functional outcome were documented at least 1 year postoperatively in 16 patellar tendon harvested patients and in 32 hamstrings harvested patients. Patellar tendon length, patella length and Insall–Salvati ratio were measured. The operated knee values were compared to the respective values of the non-operated control knees. A significant 4.2 mm or 9.7% patellar tendon shortening in patellar tendon group and a non-significant 1.14 mm or 2.6% shortening in hamstrings group was detected. No significant difference was detected in terms of major shortening—patella baja—(6% for the patellar tendon group vs. 0% for the hamsting group). There was no significant difference in anterior knee problems between the two groups as evidenced by the Shelbourne score (94 for the patellar tendon group vs. 98 for the hamsting group). Harvesting of the patellar tendon for anterior cruciate ligament reconstruction resulted in a significant shortening of the remaining tendon. In contrast harvesting of the hamstring tendons did not affect significantly the patellar tendon length. However, the incidence of patella baja and overall functional outcome was not significantly different between the two groups. Paper presented at the 12th ESSKA 2000 Congress, Innsbruck, Austria, 2006 and also presented at the 5th Biennial ISAKOS Congress, Hollywood, FL, USA, 2005.     

Is impingement the cause of jumper's knee? Dynamic and static magnetic resonance imaging of patellar tendinitis in an open-configuration system

BACKGROUND: Chronic overload is considered the main cause of patellar tendinitis, but it has been postulated that impingement of the inferior patellar pole against the patellar tendon during knee flexion could be responsible. HYPOTHESIS: The role of the patellar pole in patellar tendinitis can be determined by dynamic magnetic resonance imaging. STUDY DESIGN: Case-control study. METHODS: We compared 19 knees with patellar tendinitis and 32 asymptomatic knees of age-matched subjects using an open-configuration magnetic resonance imaging system. Dynamic sagittal images were obtained from full extension to 100 degrees of flexion with and without activation of the quadriceps muscle. The following measurements were made from the images: tendon-patella angle, anteroposterior diameter of the tendon, signal difference-to-noise ratio, the shape of the inferior patellar pole, and the location of the patellar tendon insertion. RESULTS: The tendon-patella angle was not significantly different between groups at any flexion angle, with or without quadriceps muscle activation. The insertion site of the patellar tendon differed significantly but not the shape of the inferior pole of the patella. The volume and the signal difference-to-noise ratio of zones of increased intratendinous signal as well as the anteroposterior diameter of the proximal patellar tendon were increased in symptomatic knees. CONCLUSIONS: The relationship between the patella and the patellar tendon was identical in both groups; therefore, chronic overload seems to be a major cause of patellar tendinitis.     

Imaging patellar complications after knee arthroplasty

The purpose of this study is to describe complications affecting the patella in patients with total or partial knee arthroplasty. We respectively analysed plain-film radiographs, as well as ultrasound images when acquired, in a consecutive series of 1272 patients. The mean interval from knee replacement to patellar complications was 5 years and 7 months (range, 5 months to 14 years). The complications described include fracture, instability, dislocation or luxation, necrosis of the patella, infection of the patella, erosion of the patella, patellar impingement on the prosthesis and patellar or quadricipital tendon tear. We discuss the pathological imaging findings in the patella and their differential diagnosis after knee arthroplasty. Patellar complications after knee arthroplasty are uncommon but often potentially serious.     

膝关节Ⅴ型骨挫伤的MRI诊断及临床意义

目的 评价MRI对膝关节Ⅴ型骨挫伤的诊断价值及临床意义.方法 从1672例急性膝关节外伤的MRI资料中筛选出具有Ⅴ型骨挫伤的患者,分析其膝关节MRI表现.结果 Ⅴ型骨挫伤发生率2.6%(43/1672),表现为同时累及髌骨内下缘及股骨外髁前外缘的异常信号,在T_1WI上表现为低信号,在T_2WI上表现为等或稍高信号,在压脂PDWI上为高信号,在矢状面、冠状面及横断面上均可以敏感发现.MRI上显示骨折9例,软骨损伤29例,髌骨向外半脱位或脱位27例.髌骨内侧支持带损伤37例,在横断面上显示最佳并能进行分级.结论 MRI能准确显示膝关节Ⅴ型骨挫伤,对髌骨一过性脱位的诊断和治疗有重要意义.在MR检查中发现Ⅴ型骨挫伤时应加作髌骨横断面检查,以评估髌骨内侧支持带的损伤情况.     

Transverse geniculate ligament of the knee: appearance and frequency on plain radiographs.

The aims of the study were to determine the frequency of visualization of the normal transverse geniculate ligament (TGL) of the knee on lateral plain radiographs with magnetic resonance imaging (MRI) as a reference, and to determine features that make this ligament apparent on plain radiographs. 50 consecutive lateral plain radiographs and sagittal T1-weighted images of corresponding knees were evaluated prospectively. A TGL was considered visualized on plain radiographs when an opacity of soft-tissue density was apparent in the posterior part of the Hoffa's fat pad. The TGL was identified in 29 of the 50 (58%) sagittal MR images; a TGL was observed on the lateral plain radiographs of six patients (12%). Correlation with the MR images showed that, when visualized on plain radiographs, the ligament is at least 3 mm thick and completely surrounded by fat. Our study shows that the TGL is a normal variant that can be recognized frequently on lateral plain radiographs of the knee.     

Sport injuries of the extensor mechanism of the knee

Injuries of the extensor mechanism of the knee occur frequently during sport activity. For a successful treatment they must be diagnosed early. Besides osseous structures the patellar tendon, the patella, the quadriceps muscle and tendon, retinacula and bursae can be affected. After initial clinical examination there are different noninvasive imaging modalities available for assessment of bone, cartilage, ligaments, tendons and soft tissue. Conventional radiographs are still the basic imaging tool for the clinician. Additional information about the osseous status is provided by computed tomography, whereas sonography plays an important role concerning diagnosis of soft tissue injuries. For the detection of cartilagenous, ligamentous or tendon lesions MRI is the superior non-invasive imaging modality.     

MRI of anterior cruciate ligament autografts

The purpose of this study was to assess the usefulness of MRI in the evaluation of autografts after anterior cruciate ligament reconstruction. The subjects were 110 patients with anterior cruciate ligament reconstruction using patellar tendon autografts who underwent clinical examination, MRI, and arthroscopy of the knee. T1- and T2-weighted MR images were obtained in sagittal plane. Clinical findings were categorized into three groups: normal, borderline, and abnormal. The MRI appearances of the autografts were categorized into three types: straight continuous band (type I), interrupted band (type II) and generalized increased intensity band (type III). The clinical findings and MRI findings were compared with arthroscopic findings. Ninety-six percent of the type I showed no autograft tear on arthroscopy. In comparison with the clinical findings, MRI was found to be well correlated with arthroscopic findings. In conclusion, if the clinical findings are normal, patients are to be followed-up without MRI and arthroscopy. However, if clinical findings are either borderline or abnormal, MRI should be performed prior to arthroscopy.     

Signs of patellar chondromalacia on sagittal T2-weighted magnetic resonance imaging

We incidentally noted distinctive high signal defects or fissures in the patellar articular cartilage on sagittal T2-weighted magnetic resonance (MR) images in 4 patients. At subsequent arthroscopy all 4 patients were found to have patellar chondromalacia. To determine the reliability of these signs, we retrospectively evaluated, in a blinded manner, sagittal T2-weighted MR images of the knee in 75 patients who were undergoing arthroscopic assessment of their patellar articular cartilage. We identified high signal defects or fissures in the patellar cartilage of 5 patients. Patellar chondromalacia was noted at arthroscopy in all 5 patients. Arthroscopy demonstrated patellar chondromalacia in an additional 21 patients with normal MR images. We conclude that high signal defects or fissures on sagittal T2-weighted images are useful signs of patellar chondromalacia. This single imaging sequence will, however, detect only a small number of the cartilage lesions that may be present.     

等长收缩可以减轻关节源性肌肉抑制

等长练习可以作为关节源性肌肉软弱的治疗方法,但并不清楚它怎样减轻关节源性肌肉抑制。本研究旨在探讨等长收缩减轻关节源性肌肉抑制的机制。方法对22位单侧膝关节骨关节炎患者进行股四头肌最大等长收缩和定量髌腱反射的肌电图测试,比较患膝上两者肌电波幅的减低程度。结果患膝股四头肌的最大等长收缩和定量髌腱反射波幅均显著低于健侧,而髌腱反射肌电波幅的减低程度则显著地大于股四头肌最大等长收缩肌电波幅的减低程度。等长收缩状态下,高位中枢参与了减轻抑制的作用,这个发现可作为等长练习治疗关节源性肌肉抑制的理论基础。     

Patellar and quadriceps tendon ruptures--jumper's knee

We reviewed 13 patients with end stage jumper's knee, 10 with patellar tendon ruptures, and 3 with ruptures of the quadriceps tendon to evaluate our long-term results in treating these tendon ruptures in an athletic population. The focus was on the natural history, the time until return, and the level of return, to athletic activity. Jumper's knee affected all patients to a varying degree prior to rupture. Basketball was the most common sport involved. At followup, averaging 4 1/2 years, patients underwent functional and clinical, as well as Cybex and roentgenographic, evaluations. Results indicated patellar tendon ruptures, where the ruptures are complete, have a more favorable prognosis than those of the quadriceps tendon which are incomplete. All of the latter patients continued to have quadriceps tendinitis following repair. In both groups, the poor results were obtained in patients with chondromalacia and/or patella alta. Cybex testing yielded results of greater than 100% strength in three patients with patellar tendon ruptures, but no patient with quadriceps rupture had comparable test results. There was no apparent relationship between ruptures and cortisone injections. Patellar and quadriceps tendon ruptures from indirect injury in athletes represent the end stage of jumper's knee and result from repetitive microtrauma. Excellent function usually follows repair of patellar tendon ruptures when surgery is performed early and care is taken to restore normal patellar tendon length. Results of quadriceps ruptures are less satisfactory since these ruptures are usually incomplete and all degenerative tissue may not be involved in the healing response.     

Quantification of intact quadriceps tendon, quadriceps tendon insertion, and suprapatellar fat pad: MR arthrography, anatomy, and cryosections in the sagittal plane.

OBJECTIVE: The purpose of this study was to quantify quadriceps tendon length, thickness, and insertion in relation to the suprapatellar fat pad. SUBJECTS AND METHODS: We used three methods to analyze the anatomy of intact quadriceps tendons and insertions into the patellar base: MR arthrography (53 knees with intact extensor mechanisms), gross anatomy (16 cadaveric knees), and cryosections (four cadaveric knees). With an electronic cursor, two observers independently quantified the extensor mechanism on midline sagittal T1-weighted spin-echo sequences acquired on a low-field-strength (0.23 T) scanner. RESULTS: On MR arthrograms, quadriceps tendon length, determined from the superior patellar pole to the most superior part of the suprapatellar recess, measured 49 +/- 7 mm in women and 50 +/- 9 mm in men. Thickness of quadriceps tendon at three sites (suprapatellar recess, center, and superior patellar pole) measured 7 +/- 1 mm in women and 8 +/- 1 mm in men. Thickness was significantly larger in men at all measurement locations. Quadriceps tendon insertion and the suprapatellar fat pad along the patellar base measured 16 +/- 2 and 6 +/- 2 mm, respectively, in women, and 18 +/- 3 and 7 +/- 2 mm, respectively, in men. CONCLUSION: On midline MR images, sagittal thickness of the quadriceps tendon and its insertion was significantly larger in men than in women. The prevalence of the suprapatellar fat pad was 100%.     

MRI appearances of the asymptomatic patellar tendon on gradient echo imaging

Thickening of the patellar tendon and foci of increased signal intensity have been described as characteristic features of jumper's knee (chronic patellar tendinitis) on magnetic resonance imaging (MRI). It was our impression that such appearances may be seen in the patellar tendons of patients without symptoms referable to the anterior part of the knee when using gradient echo images. The appearances of the asymptomatic patellar tendon on three-dimensional gradient echo sequences were studied by retrospectively reviewing the images of 60 patients, none of whom had symptoms related to the anterior part of the knee. The anteroposterior width of the patellar tendon was measured at three levels (superior, middle and inferior) on the central sagittal image of a gradient echo sequence. The relative signal intensities at the same levels were recorded. In 97% of subjects the superior part of the tendon was wider than the midpoint, and in 97% the inferior part was wider than the midpoint. The range of widths was wide, and there was no significant difference between sexes. Focal increased signal intensity in the superior part was shown in 75%, and in the inferior part in 43%. The asymptomatic patellar tendon shows uniform thickness throughout most of its length, but there are focal expansions at the proximal and distal ends. It usually demonstrates low signal on MRI, but may contain foci of increased signal intensity at either or both ends when imaged on gradient-echo sequences.     

关节源性肌肉抑制的定量腱反射肌电图检查

目的 :膝关节骨关节炎 (kneeosteoarthritis,膝OA )可造成关节源性肌肉抑制 (arthrogenousmuscleinhibition ,AMI)和肌肉软弱。以往AMI的测定方法均有不足处。本研究旨在使用定量腱反射肌电图检查来诊断评价AMI。方法 :对 36例单侧膝OA患者进行股神经最大电刺激、定量的髌腱反射肌电图检查 ,比较健患侧电生理参数的差异。同时作股神经最大电刺激和定量髌腱反射时 ,肌电波幅减低程度之间的比较。另外 ,对 8例志愿者 (16个肢体 )作了定量腱反射的准确度检验。结果 :健侧与患侧相比 ,膝OA的股神经最大电刺激的肌电波幅与潜伏期无显著差别 ,但患侧定量髌腱反射肌电波幅却显著地低于健侧。另外 ,定量髌腱反射肌电波幅的减低程度显著地大于股神经最大电刺激肌电波幅的减低程度。 36例患者中 ,有 2 5例 (6 9 4% )表现出明显的肌肉抑制。在志愿者定量腱反射肌电图检查的准确度检验中 ,算出的平均变异系数为 0 0 71,且两侧反射波幅的差值基本在 10 %以内。小结 :在电刺激表明肌萎缩不明显的前提下 ,定量腱反射的肌电图检查显示膝OA的股四头肌有明显的AMI,此关节源性肌肉抑制为脊髓前角运动神经元的抑制。     

MRI criteria for patella alta and baja

Objective To determine the range of the patellar tendon length to patellar length ratio on magnetic resonance imaging (MRI) of the knee in order to aid in the establishment of MRI criteria for patella alta and baja.Patients Two hundred and forty-five patients ages 6–85 (mean 44) years who went through 262 consecutive 1.5 MRI studies of the knee performed during November 2000 through February 2001 were evaluated, regardless of their clinical symptoms.Design Patellar length (PL) and patellar tendon length (TL) were measured by a single musculoskeletal radiologist on sagittal images by a line connecting the superior and inferior patellar poles and the shortest length of the inner margin of the tendon respectively. TL/PL ratio was subsequently calculated. The distribution of ratios was evaluated; the extreme 2.5% at each end of the distribution was defined as patella alta and baja.Results The TL/PL ratio ranged between 0.56 and 1.71 (mean 1.05). After plotting the ratios, we noted an asymmetric curve skewed to the left. Based upon calculation of the extreme 2.5% of the ratio at each end of the plot, we determined that the MRI definition of patella alta and baja is a ratio of TL/PL of more than 1.50 and less than 0.74 respectively. We found that females had significantly higher TL/PL ratio than males (1.0878 and 1.0032 respectively). Ratios defined for patella alta and baja were 1.52 and 0.79 respectively in females and 1.32 and 0.74 respectively in males (p<0.0001).Conclusion Patella alta and baja are determined as TL/PL of more than 1.50 and less than 0.74 respectively, somewhat different than traditionally quoted radiographic and previously described MRI criteria.     

Quadriceps fat pad signal intensity and enlargement on MRI: prevalence and associated findings

OBJECTIVE: The purpose of this investigation was to characterize the MRI appearance of the quadriceps fat pad and to correlate the findings with other knee abnormalities, anatomic measurements of the extensor mechanism, and findings from history and at physical examination. MATERIALS AND METHODS: Ninety-two consecutive knee MRI examinations from 84 patients were retrospectively reviewed by two musculoskeletal radiologists for quadriceps fat pad enlargement and signal intensity. Other data from the retrospective review included infrapatellar and prefemoral fat pad signal intensity, quadriceps and patellar tendon abnormalities, joint effusion, medial plica, chondromalacia, articular muscle thickness, and prepatellar edema. The patellar length, patellar articular length, patellar tendon length, and femoral sulcus angle were measured. MRI reports were reviewed for meniscal and ligament abnormalities. Clinical data were reviewed for findings of anterior knee pain in the history and at physical examination. The chi-square and Student's t tests were used to determine significant associations. RESULTS: Twelve percent (11/92) of MRI examinations showed quadriceps fat pad mass effect on the suprapatellar recess, which was associated with intermediate or fluid signal intensity of the quadriceps fat pad (chi(2) = 7.19, p = 0.0274) but with no other findings on knee MRI. Anterior knee pain at physical examination was associated with quadriceps fat pad mass effect (chi(2) = 8.76, p = 0.0031), medial collateral ligament abnormality (chi(2) = 4.83, p = 0.0031), and history of anterior knee pain (chi (2) = 22.76, p < 0.0001). CONCLUSION: Enlargement of the quadriceps fat pad on MRI has a prevalence of 12% and is significantly associated with intermediate or fluid signal intensity of the quadriceps fat pad and anterior knee pain.     

Relationship between symptoms of jumper's knee and the ultrasound characteristics of the patellar tendon among high level male volleyball players

This study assessed the ultrasound characteristics of the patellar tendon in two groups of volleyball players, one group without knee symptoms and one group with symptoms of jumper's knee. Of 47 male elite players, 25 were diagnosed to have current and seven to have had previous symptoms of jumper's knee, as determined by clinical examination. Since some players had bilateral problems, there were 34 knees with current problems and nine with previous problems. Seven of the 30 knees with a clinical diagnosis of jumper's knee in the patellar tendon had normal ultrasound findings, and ultrasound changes believed to be associated with jumper's knee (tendon thickening, echo signal changes, irregular paratenon appearance) were observed in 12 of 51 knees without symptoms. Specific ultrasound findings such as paratenon changes, hypoechoic zones or pathological tendon thickness proximally did not correlate significantly with the degree or the duration of symptoms. This study suggests that the specificity and sensitivity of ultrasonography is low in the evaluation of patients with mild symptoms of jumper's knee.     

MR imaging of patellar tendinitis.

To identify magnetic resonance (MR) imaging characteristics of normal patellar tendons and those affected by tendinitis, the authors evaluated MR images obtained in 10 healthy volunteers, in 50 patients who underwent MR imaging for evaluation of knee structures other than the patellar tendon, in 11 patients with patellar tendinitis, and in two athletes with patellar tendon injuries. Normal tendons had uniformly low signal intensity on T1-, T2-, and proton-density-weighted images and displayed distinct margins, and the anteroposterior (AP) diameter slightly increased proximally to distally. It was concluded that the AP diameter of a normal tendon, in its proximal portion, should not exceed 7 mm. In patellar tendinitis, the tendon showed increased signal intensity on T1-, T2-, and proton-density-weighted images and increased AP diameter proximally. The margins of affected tendons were indistinct, especially posterior to the thickened segment. In all groups studied, women had thicker proximal tendons than did men.