Recesses along the posterior margin of the infrapatellar (Hoffa’s) fat pad: prevalence and morphology on routine MR imaging of the knee

The objective is to evaluate the prevalence and morphology of recesses along the posterior margin of the infrapatellar fat pad on routine MR imaging of the knee. MR images of 213 knees in 204 consecutive individuals were evaluated with regard to the prevalence and morphology of recesses (a suprahoffatic recess close to the inferior border of the patella and the previously described infrahoffatic recess anterior to the inferior portion of the infrapatellar plica). The recesses were analyzed with regard to synovial effusion and the condition of the anterior cruciate ligament (ACL). Anatomic dissection was made in 29 knees in 16 cadavers to verify the presence of the suprahoffatic recess. The infrahoffatic recess was present in 45% of the knees and mostly linear in shape (44%). The suprahoffatic recess was detected in 71% of the knees (45% in cadavers). Very weak to moderate positive correlation was found between the synovial effusion or the condition of the ACL and the presence and dimensions of the recesses. An awareness of the recesses in the infrapatellar fat pad is important in order to distinguish between pathology and anatomic variants on routine MR imaging of the knee.     

Clinical consequences of bone bruise around the knee

The aim of this study is to evaluate the relation between bone bruise and (peri-)articular derangement and to assess the impact of bone bruise on presentation and short term course of knee complaints. We recorded MR abnormalities in 664 consecutive patients with sub-acute knee complaints. Patients were divided in four groups: patients with and without intra-articular knee pathology, subdivided in patients with and without bone bruise. We assessed function and symptoms at the time of MR and 6 months thereafter. Bone bruises were diagnosed in 124 of 664 patients (18.7%). Patients with bone bruise had significantly more complete ACL, lateral meniscal, MCL and LCL tears. Both with and without intra-articular pathology patients with bone bruise had a significantly poorer function at the time of MR (Noyes score of, respectively, 313.21 versus 344.81 and 306.98 versus 341.19). Patients with bone bruise and intra-articular pathology showed significantly more decrease in activity (decrease of Tegner score from 6.28 to 2.12 versus 5.70–2.55). At 6 months there were no significant differences in clinical parameters between the four groups. We concluded that bone bruise in combination with MCL tear is an important cause of initial clinical impairment in patients with sub-acute knee complaints. Clinical improvement within 6 months is more pronounced than in patients without bone bruise.     

Functional improvement after unicompartmental knee replacement: a follow-up study with a performance based knee test

In literature no reports appear on functional recovery of unicompartmental knee replacement using both subjective and objective methods. Functional aspects are especially of importance, since prosthetic replacement is considered more often in younger patients, who require an optimal knee function for activities such as sports. In a prospective study on 38 patients with a mean age of 62.2 years functional improvement was measured. Using Knee Society Score (KSS) as a clinician based score and the Dynaport^® Knee Test as a functional test measurements were performed at preoperative, 3 and 6 months, 1 and 2 years, after surgery. The Dynaport^® Knee Test is an accelerometer-based system that objectively measures functional aspects of gait during various tasks of daily life. It consists of four sub scores. The KSS assesses pain and function. Both scores range from 0 to 100. The mean KSS preoperative was 44.0 and improved significantly to 81.7 at 3 months (P < 0.001) and to 87.4 (P = 0.025) at 6 months. No significant differences were noted after 6 months. The mean preoperative Dynaport^® Knee Test score was 35.8 and at 3 months 43.6 (P < 0.001), 48.6 at 6 months (P < 0.001). No significant differences were noted after 6 months follow-up. Of the Dynaport sub scores, the low demanding tasks Lift and Move and Locomotion, cease to improve beyond 6 months. The high demanding task Transfers only improved up to 3 months. However, the other high demanding tasks Rise and Descend showed improvement beyond 1 year after surgery, since the improvement from 6 months to 2 years was significant (P = 0.023). This study has found that functional recovery continues beyond 6 months and even up to 2 years. It seems only more challenging tests can discriminate on improvement beyond a point where questionnaires cease to improve. The use of objective measurement methods is advocated next to the clinician based scores and self reported questionnaires.     

High resolution computed tomography of knee menisci

Sixty four menisci in 22 patients were examined by non-contrast high resolution computed tomography (CT). Fifty four menisci were imaged on a GE 8800 CT scanner. The other 10 were imaged on a GE 9800 CT scanner. Nineteen menisci were shown to be torn on arthrography and/or arthroscopy—12 medially and 7 laterally. The remaining menisci were normal. When the meniscal CTs were reviewed collectively by three observers without knowledge of arthrographic or arthroscopic results, sensitivity was 63%, specificity was 93%, and accuracy was 84%. Although only 10 menisci were imaged on the GE 9800 scanner, the sensitivity in this subset of scans was 83%, the specificity 100%, and the accuracy was 90%. These results suggest that noncontrast CT cannot replace arthrography or arthroscopy, but it is possible that images obtained on the GE 9800 or comparable CT scanner may be accurate enough to be used for screening of meniscal tears in selected patients.     

MRI in assessment of sports related knee injuries

Purpose

To investigate the accuracy of MRI in assessment of sports related knee injuries.

Materials and methods

From August 2012 to March 2013 thirty patients referred for sports related knee pain have been included in this study. Patients were subjected to a dedicated MR knee study and correlated knee arthroscopy and surgery.

Results

The study included thirty patients complaining of sports related knee pain, only 5 patients (16.6%) were with normal MRI findings and 25 patients (83.4%) were with abnormal MRI findings. Among the 25 patients who had injuries of their knees, 15 patients (60%) had ACL injuries, 2 patients (8%) had PCL injuries, 10 patients (40%) had meniscal injuries, 8 patients (32%) had collateral ligament injuries, 5 patients (20%) had bone injuries and 2 patients (8%) had muscular injuries. Only 7 patients (28%) were represented with isolated injury and 18 patients (72%) were represented with combined injuries. In correlation with arthroscopies and surgeries, morphological analysis was true-positive in 23 (92%) patients of the 25 injured patients, and true-negative in 3 (60%) patients of the 5 normal patients. Morphological analysis revealed overall 92% sensitivity and 60% specificity. Regarding the 15 patients who had ACL injuries, 13 patients (86.6%) were true-positive and 8 patients (80%) of the 10 patients who had meniscal injuries were true-positive.

Conclusion

MRI represents the optimal imaging tool in the evaluation of the sports related knee injuries, which has been shown to be an accurate and non invasive method of diagnosing ligament, meniscal, cartilage and muscular knee injuries.     

Fully automated software to monitor wear in prosthetic knees using fluoroscopic images

Total knee arthroplasty is now a widely accepted treatment for late-stage arthritis. Wear of the polyethylene layer in prosthetic knees is a known cause of implant failure. Early detection of wear may allow prediction of device failure. In this paper we describe a fully automated image processing algorithm to measure the minimum tibiofemoral joint space width (mJSW) for monitoring prosthesis wear radiographically. The femoral portion and tibial plate were automatically delineated and mJSW was calculated in each compartment. The software also delineated the tip of the prosthesis pin in order to make a magnification correction. The algorithm was tested with a set of triplicate acquisitions of 18 fluoroscopic knee images. The RMS standard deviation (RMSSD) for the triplicate measurements was calculated as a figure of merit. The RMSSD was 0.077 and 0.087 mm for the lateral and medial compartments. The computer successfully found the minimum JSW for both compartments in all 54 images. A single case (2% of total) required user interaction to correct for an obvious failure to delineate the prosthesis pin. We document a robust and precise tool for quantifying mJSW to monitor prosthesis wear.     

The flipped meniscus sign

Meniscal fragments may be difficult to detect on magnetic resonance (MR) imaging and yet are clinically significant. This paper describes and illustrates the MR appearance of an easily overlooked meniscal fragment. Ten knees, each appearing to show an abnormally large anterior meniscal horn (8 mm or more in height) were prospectively identified on MR images. In each case demonstrable large tears of the ipsilateral posterior horns were present (same meniscus as had large anterior horns). The lateral meniscus was involved in nine cases and the medial in one. Two of the ten patients imaged had surgically proven bucket-handle meniscal tears as well as meniscal fragments overlying the ipsilateral anterior horn. In one case previous MR imaging at our institution had demonstrated the affected anterior horn to be of normal caliber. The striking MR appearance of an abnormally enlarged anterior meniscal horn in association with a tear of the ipsilateral posterior horn suggests the presence of a meniscal fragment or of a posteriorly detached bucket-handle tear of the posterior horn of the meniscus.Presented at the Fifteenth Annual Skeletal Symposium of the Hospital of the University of Pennsylvania at Sun Valley, Idaho, USA, on 3 March 1992     

Differences in knee adduction moment between healthy subjects and patients with osteoarthritis depend on the knee axis definition

ObjectiveThis study, firstly, investigates the effect of using an anatomical versus a functional axis of rotation (FAR) on knee adduction moment (KAM) in healthy subjects and patients with knee osteoarthritis (KOA). Secondly, this study reports KAM for models with FAR calculated using weight-bearing and non-weight-bearing motion.DesignThree musculoskeletal models were created using OpenSim with different knee axis of rotation (AR): transepicondylar axis (TEA); FAR calculated based on SARA algorithm using a weight-bearing motion (wFAR) and a non-weight-bearing motion (nwFAR). KAM were calculated during gait in fifty-nine subjects (n = 20 healthy, n = 16 early OA, n = 23 established OA) for all models and groups.ResultsSignificant differences between the three groups in the first peak KAM were found when TEA was used (p = 0.038). However, these differences were no longer present when using FAR. In subjects with established OA, KAMs were significantly reduced when using nwFAR compared to TEA models but also compared to wFAR models.ConclusionThe presence of excessive KAM in subjects with established KOA showed to be dependent on the definition of the AR: anatomical versus functional. Therefore, caution should be accounted when comparing KAM in different studies on KOA patients. In patients with end-stage knee OA where increased passive knee laxity is likely to exist, the use of weight-bearing motions should be considered to avoid increased variability in the location and orientation of a FAR obtained from activities with only limited joint loading.     

Arthroscopic treatment of patients with moderate arthrofibrosis after total knee replacement

The purpose of this study was to document the effect of arthroscopic management in patients with knee stiffness after total knee replacement. We present a case series study, in which 32 patients have been treated for moderate arthrofibrosis of the knee after total knee replacement, with the same regimen. We have excluded all cases of stiffness, because of infection, mechanical mal-alignment, loosening of the implants and other obvious reasons of stiffness of the knee, rather than pure arthrofibrosis. All patients first underwent a trial of conservative treatment before going for arthroscopic management. A pain catheter for femoral nerve block was inserted just before anesthesia for post-operative pain management. Arthroscopic arthrolysis of the intra-articular pathology was performed in a standardized technique with release of all fibrous bands in the suprapatellar pouch, reestablishing the medial and lateral gutter, release of the patella, resection of the remaining meniscal tissue or an anterior cyclops, if needed. Intensive physiotherapy and continuous passive motion were to start immediately post-operatively. All the patients were available for the follow up and they were evaluated using the knee society rating system. A total of 25 of the 32 procedures resulted in an improvement of the patients knee score. All the knees operated upon had intra-articular fibrous bands, hypertrophic synovitis and peri-patellar adhesions. A total of eight patients suffered from an anterior cyclops lesion and six patients showed pseudomenicus. In 19 cases a medial and lateral relapse of the patella was performed; only 5 patients got an isolated lateral release. The mean knee flexion was 119° (100–130) at the end of arthroscopy and was 97° (75–115) at the last follow up. The eight patients with extension lags decreased from 27° (10°–35°) pre-operatively to 4° (0–10) at time of follow up. The average knee society ratings increased from 70 points prior to the arthroscopy to 86 at time of follow up, which was found to be statistically significant (P < 0.01, student’s t test). The average function score also showed improvement from 68 points pre-operatively to 85 at the time of final follow up. The average pain scores improved from 30 points pre-operatively to 41 at the time of final follow up. Our results showed that arthroscopic management of knee stiffness following total knee replacement is a safe and efficient method of treatment. Pain and functional knee scores can improve markedly.     

Characteristics of clinical measurements between biomechanical responders and non-responders to a shoe designed for knee osteoarthritis

PurposeThe purpose of this study was to investigate the characteristics of biomechanical and clinical measurements in relation to the knee adduction moment when wearing a standard shoe and a shoe design for individuals with knee osteoarthritis (Flex-OA).MethodsKinematic and kinetic data were collected from thirty-two healthy individuals (64 knees) using a ten camera motion analysis system and four force plates. Subjects performed 5 walking trials under the two conditions and the magnitude of individuals’ biomechanical responses where explored in relation to the clinical assessment of the Foot Posture Index, hip rotation range, strength of hip rotators, and active ankle-foot motion, all of which have been described as possible compensation mechanisms in knee osteoarthritis.ResultsSignificant reductions in the first peak of the knee adduction moment (KAM) during stance phase (9.3%) were recorded (p < 0.0001). However, despite this difference, 22 of 64 knees showed either no change or an increased KAM, indicating a non-response or negative-response to the Flex-OA shoe. Significant differences were observed between the responder and non-responder subgroups in the hip rotation range ratio (p = 0.044) and the hip rotators strength ratio (p = 0.028).ConclusionSignificant differences were seen in clinical assessments of hip rotation range and hip rotator strength between responders and non-responders using a cut-off of 0.02 Nm/kg change in the KAM.     

Knee loading patterns of the non-paretic and paretic legs during post-stroke gait

BackgroundPost-stoke gait disorders could cause secondary musculoskeletal complications associated with excessive repetitive loading. The study objectives were to 1) determine the feasibility of measuring common proxies for dynamic medial knee joint loading during gait post-stroke with external knee adduction (KAM) and flexion moments (KFM) and 2) characterize knee loading and typical load-reducing compensations post-stroke.MethodsParticipants with stroke (n = 9) and healthy individuals (n = 17) underwent 3D gait analysis. The stroke and healthy groups were compared with unpaired t-tests on peak KAM and peak KFM and on typical medial knee joint load-reducing compensations; toe out and trunk lean. The relationship between KAM and load-reducing compensations in the stroke group were investigated with Spearman correlations.ResultsMean (SD) values for KAM and KFM in the healthy group[KAM = 2.20 (0.88)%BW*ht; KFM = 0.64 (0.60)%BW*ht] were not significantly different from the values for the paretic [KAM = 2.64 (0.98)%BW*ht; KFM = 1.26 (1.13)%BW*ht] or non-paretic leg of the stroke group[KAM = 2.23(0.62)%BW*ht; KFM = 1.10 (1.20)%BW*ht]. Post hoc one sample t-tests revealed greater loading in stroke participants on the paretic (n = 3), non-paretic (n = 1) and both legs (n = 2) compared to the healthy group. The angle of trunk lean and the angle of toe out were not related to KAM in the stroke group.DiscussionMeasurement of limb loading during a gait post-stroke is feasible and revealed excessive loading in individuals with mild to moderate stroke compared to healthy adults. Further investigation of potential joint degeneration and pain due to repetitive excessive loading associated with post-stroke gait is warranted.     

膝关节外伤性骨挫伤的MR诊断及临床意义

目的评价MRI对骨挫伤的诊断价值和临床意义。方法选取145例x线平片未显示股骨和胫骨骨折但MRI显示有外伤性骨髓水肿的膝关节外伤患者，MR检查时间为外伤后1-3d，采用膝关节专用线圈，快速SE（FSE）序列，T，WI、T2WI、质子密度加权成像（PDWI）＋脂肪抑制，行冠状面、矢状面、横断面、斜矢状面扫描，层厚3min，层间距0．5mm。根据骨髓水肿的分布，将膝关节外伤性骨挫伤分成5类：轴向旋转性损伤、夹击损伤、仪表盘式损伤、过伸型损伤和髌骨外侧脱位。其中48例行关节镜检查。结果145例中MRI显示轴向旋转性损伤43例，夹击损伤53例，仪表盘式损伤40例，过伸型损伤9例。骨髓水肿在PDWI或T2WI脂肪抑制序列上为片状地图样高信号，在T1WI上为低信号，边界不清。48例行关节镜检查，发现前交叉韧带撕裂11例，后交叉韧带撕裂13例，半月板撕裂22例，5例MRI诊断半月板撕裂而关节镜未能显示，MRI诊断与关节镜诊断结果符合率为89．6％。结论MRI可以准确显示膝关节骨挫伤的部位和范围及膝关节附属结构的损伤，推断其受伤机制，对临床诊断、治疗具有重要意义，应作为常规检查方法应用。     

Likelihood of knee replacement surgery up to 15 years after sports injury: A population-level data linkage study

ObjectivesKnee injury is strongly associated with the development of knee osteoarthritis. While there is preliminary evidence for an increased risk of knee replacement (KR) surgery after sports injury, no studies have investigated this at a population level. This population-level study aimed to quantify the likelihood of KR surgery and direct healthcare costs 10–15 years after sports injury.DesignStatewide population-based cohort study.MethodsThe cohort was established by linking two key administrative datasets capturing all hospital admissions and emergency department (ED) presentations in Victoria, Australia. Sports injury presentations from 2000–2005 and KR admissions from 2000–2015 were identified using ICD-10-AM codes. A Cox proportional hazards model estimated likelihood of KR using time to surgery admission data, adjusting for potential confounders. KR costs for the sports-injured cohort were estimated from the health system perspective using diagnosis codes and national hospital cost weights.ResultsOver the study period there were 64,038 sports injuries (including 7205 knee injuries) resulting in ED presentation or hospitalisation, and 326 KR procedures. Multivariate analysis showed that having a knee injury more than doubled the hazard of subsequent KR (hazard ratio 2.41, 95%CI 1.73–3.37), compared to all other sports injuries. Direct healthcare costs for KR totaled $AUD7.93 million for the cohort, with 21% of costs attributable to the knee injury group.ConclusionsSports-related knee injury manifests in a significantly greater likelihood of KR, at considerable cost to society. Targeted health policy and effective interventions are needed to prevent sports-related knee injuries and contain this substantial burden.     

Comparing walking biomechanics of older females in maximal,minimal, and traditional shoes

BackgroundKnee osteoarthritis (OA) is a degenerative joint disease that affects millions of individuals each year. Several biomechanical variables during walking have been identified as risk factors for developing knee OA, including the peak external knee adduction moment (KAM) and the knee flexion angle at initial contact. Many interventions have been studied to help mitigate these risk factors, including footwear. However, it is largely unknown how varying shoe cushioning may affect walking biomechanics related to knee OA risk.Research QuestionWhat is the effect of maximally and minimally cushioned shoes on walking biomechanics compared to a traditionally cushioned shoe in older females?MethodsWalking biomechanics in three shoes (maximal, traditional, minimal) were collected on 16 healthy females ages 50–70 using an 8-camera 3D motion capture system and two embedded force plates. Key biomechanical variables related to knee OA disease risk were compared between shoes using repeated measures ANOVAs.ResultsThe KAM was significantly larger in the maximal shoe (p = 0.005), while the knee flexion angle at initial contact was significantly larger in both the maximal and minimal shoe compared to the traditional shoe (p = .000). Additionally, the peak knee flexion angle (p = .000) and the loading rates of the vertical ground reaction force were (instantaneous: p = 0.001; average: p = .010) were significantly higher in the minimal shoe.SignificanceWhile these results are specific to the shoes used in this study, clinicians should exercise caution in prescribing maximal or minimal shoes to females in this age group who may be at risk of knee OA given these results. Research is needed on the effect of these shoes in patients with knee OA.     

自体中1/3股二头肌腱和股薄肌重建膝关节后外侧角韧带复合体损伤

目的 探讨采用自体中1/3股二头肌腱和股薄肌重建膝关节后外侧角韧带复合体(PLC)的技术及近期的疗效. 方法 本组21例,均为联合型的直向外侧+后外侧旋转＞Ⅱ度不稳定,重建范围:胭肌腱、外侧副韧带、胭腓韧带.术中单独提取健侧或患侧股薄肌重建膕肌腱.切取股二头肌肌腱中1/3部,折叠后对折端拉入股骨外髁骨隧道固定,分出的前束重建外侧副韧带(LCL),后束重建胭腓韧带. 结果 术后随访6～24个月,平均16个月.Lyshohn膝关节功能评分,术前为(43±2)分,术后半年为(90±3)分,有明显改进. 结论 PLC损伤可造成患肢功能受损,采用自体中1/3股二头肌腱和股薄肌修复重建韧带手术可获得良好预后.     

膝关节交叉韧带损伤的MRI诊断

目的 :探讨MRI对膝关节交叉韧带损伤的诊断价值。方法 :回顾性分析 2 5例经手术或关节镜证实的前、后交叉韧带损伤患者 ,MR检查采用SE、TSE矢状位、冠状位及横断位T1WI、T2 WI及STIR。结果 :2 5例交叉韧带损伤中 ,部分性撕裂 16例 ,完全性撕裂 9例。MRI诊断交叉韧带部分性撕裂和完全性撕裂的符合率分别为 87.5 %和 88.9%。结论 :MR能较准确地诊断膝关节交叉韧带损伤及其并发症 ,为临床制订治疗方案提供可靠依据。     

Magnetic resonance imaging of knee trauma

This article reviews the magnetic resonance (MR) appearance of normal knee anatomy and the role of MRI in the evaluation of knee trauma. Images acquired in the sagittal plane are the most useful. A combination of T₁- and T₂-weighted spin echo pulse sequences is most commonly employed. A meniscal tear is identified by an intrameniscal signal which extends to the joint surface. MR and arthroscopic findings agree in more than 90% of patients. It is important to be familiar with the MRI appearance of normal anatomic variants that may be confused with meniscal tears: the transverse geniculate ligament, the hiatus of the popliteal tendon sheath, and the meniscofemoral ligaments. Tears in the anterior cruciate, posterior cruciate, and collateral ligaments are also depicted.The following article is one in a series of review articles which represent expansions of papers presented at the annual meeting of the International Skeletal Society and were solicited by the editors     

CT Arthrography and Virtual Arthroscopy in the Diagnosis of the Anterior Cruciate Ligament and Meniscal Abnormalities of the Knee Joint

Objective

To determine the diagnostic accuracy of CT arthrography and virtual arthroscopy in the diagnosis of anterior cruciate ligament and meniscus pathology.

Materials and Methods

Thirty-eight consecutive patients who underwent CT arthrography and arthroscopy of the knee were included in this study. The ages of the patients ranged from 19 to 52 years and all of the patients were male. Sagittal, coronal, transverse and oblique coronal multiplanar reconstruction images were reformatted from CT arthrography. Virtual arthroscopy was performed from 6 standard views using a volume rendering technique. Three radiologists analyzed the MPR images and two orthopedic surgeons analyzed the virtual arthroscopic images.

Results

The sensitivity and specificity of CT arthrography for the diagnosis of anterior cruciate ligament abnormalities were 87.5%-100% and 93.3-96.7%, respectively, and those for meniscus abnormalities were 91.7%-100% and 98.1%, respectively. The sensitivity and specificity of virtual arthroscopy for the diagnosis of anterior cruciate ligament abnormalities were 87.5% and 83.3-90%, respectively, and those for meniscus abnormalities were 83.3%-87.5% and 96.1-98.1%, respectively.

Conclusion

CT arthrography and virtual arthroscopy showed good diagnostic accuracy for anterior cruciate ligament and meniscal abnormalities.