Spontaneous osteonecrosis of the knee involving both the medial femoral condyle and the medial tibial plateau: report of three cases

Spontaneous osteonecrosis of the knee (SPONK) usually involves a single condyle or plateau. The medial femoral condyle (MFC) is most often involved and spontaneous osteonecrosis of the medial tibial plateau (MTP) is a rare condition, representing only 2% of all necroses reported in the knee. SPONK involving both the MFC and the MTP is extremely rare. SPONK occurring in either the MFC or the MTP individually might extend to the corresponding side of the knee in the advanced end-stage; however, in that situation, significant degenerative changes would exist and it might be difficult to differentiate end-stage SPONK form severe osteoarthritis. SPONK affecting both the MFC and the MTP without significant secondary osteoarthritic changes has not been reported, even though it is difficult to know which occurs first. We have cared for three patients with histologically proven osteonecrosis of the MFC and MTP and report their radiologic features.     

Spontaneous osteonecrosis of the knee. Scintigraphic findings

Three cases of spontaneous osteonecrosis (SON) of the knee, comprised of two cases involving the medial tibial plateau and one involving the medial femoral condyle, are reported. Because of the relatively normal x-rays early in the course of the disease, the differential diagnosis of a painful knee is markedly shortened with the typical scintigraphic findings in SON. The scintigraphic findings represent a focal area of increased activity at the affected site on a three-phase bone scan.     

Osteonecrosis of the knee after arthroscopic surgery: diagnosis with MR imaging

Spontaneous osteonecrosis about the knee typically is a disease of the elderly characterized by an acute onset of pain. The exact cause of this condition has long been debated, although a causative relationship between meniscal tears and spontaneous osteonecrosis about the knee has been postulated. Seven patients with knee pain, meniscal tears, and chondromalacia without initial evidence of osteonecrosis at magnetic resonance (MR) imaging underwent arthroscopic surgery with meniscal recontouring or repair and cartilage shaving. These patients returned within 2-14 months with recurrent pain in the treated knee. MR imaging then demonstrated abnormalities consistent with osteonecrosis. Osteonecrosis of the femoral condyle or tibial plateau may be a late sequela of meniscal injury in association with chondromalacia and arthroscopic surgery. This diagnosis should be suspected in patients with recurrent knee pain after arthroscopic repair of meniscal tears. The precise relationship of this pattern of osteonecrosis to that previously described as spontaneous requires further investigation.     

Occult fracture patterns of the knee associated with anterior cruciate ligament tears: assessment with MR imaging.

One hundred consecutive magnetic resonance (MR) images of the knee in patients with acute complete anterior cruciate ligament (ACL) tears were reviewed to evaluate the prevalence and patterns of associated occult fractures. Eighty-nine occult fractures were identified in 56 knees. All occult fractures were in the posterior aspect of the lateral tibial plateau. Of these, occult fractures were isolated in 24 cases (43%) and were in combination with fractures in the middle aspect of the lateral femoral condyle in 26 (46%), with fractures in the posterior aspect of the medial tibial plateau in four (7%), and with fractures involving all three areas in one (2%). Disruption of the ACL under valgus stress leads to anterior translation of the tibia and relative external rotation of the femur. This allows impaction of the posterior portion of the lateral tibial plateau against the middle of the lateral femoral condyle and accounts for the unique pattern of occult fractures associated with ACL tears. An occult fracture of the posterior lateral tibial plateau with or without an associated fracture in the lateral femoral condyle ("kissing contusion") is a relatively frequent finding in acute ACL tears and, when present, is highly suggestive of such an associated tear.     

Spontaneous collapse of the tibial plateau: radiological staging

Objective This paper proposes a radiological staging system for necrosis of the tibial plateau, similar to those already developed for the hip and the medial femoral condyle.Design and patients We retrospectively studied the clinical case histories and radiographic findings of 14 patients (15 affected knees) with histologically proven osteonecrosis of the tibial plateau.Results Stage I was marked by normal radiograph, but increased uptake in bone scan and subchondral areas of abnormal marrow signal intensity in magnetic resonance imaging (MRI), as reported in other osteonecrosis sites. Stage II was characterised by cystic and sclerotic changes, and stage III fracture of the medial rim of the medial tibial plateau and tibial plateau collapse were present. Stage IV was marked by joint narrowing. These changes appeared earlier and were more pronounced when there was genu varum/valgum or involvement of the lateral tibial plateau.Conclusions The radiological evolution of the disease appears to follow a four-stage course over a period of roughly one year from the onset of symptoms.     

Spontaneous osteonecrosis of the knee associated with ipsilateral tibial plateau stress fracture: report of two patients and review of the literature

Two cases are presented of spontaneous osteonecrosis of the knee (SONK) associated with stress fractures of the tibial plateau. This association lends further credence to the postulate that SONK has a traumatic etiology. Received: 9 May 2000 Revision requested: 15 June 2000 Revision received: 31 August 2000 Accepted: 4 September 2000     

Frequency and topography of lesions of the femoro-tibial cartilage at spiral CT arthrography of the knee: a study in patients with normal knee radiographs and without history of trauma

OBJECTIVE: To determine the frequency and topography of cartilage lesions involving the femoro-tibial joints in patients with normal knee radiographs and without a remembered history of trauma. DESIGN AND PATIENTS: A radiologist retrospectively reviewed the dual-detector spiral CT knee arthrograms performed in 209 consecutive patients (mean age 37.6 years) with normal knee radiographs. Images were analyzed for the presence, grade (Noyes classification system) and location of cartilage lesions, the location being designated by dividing each articular surface into a grid of 16 parts. RESULTS: Fifty-three percent of knees had cartilage lesions of grade 2A or higher that involved articular surfaces to a variable extent: lateral tibial plateau (31%), medial femoral condyle (27%), medial tibial plateau (14%) and lateral femoral condyle (5%). Areas of the posterior half of the lateral tibial plateau and of the inner half of the medial femoral condyle were statistically more frequently involved than their counterparts (P<0.0001). The bare area of the medial tibial plateau, but not that of the lateral tibial plateau, was more frequently involved than the corresponding meniscus-covered area (P<0.0001). CONCLUSION: Cartilage lesions of grade 2A or higher, detected at spiral CT arthrography in 53% of the knees, predominantly involved the posterior half of the lateral tibial plateau, the inner half of the medial femoral condyle and the bare area of the medial tibial plateau.     

Artificial bone grafting [calcium hydroxyapatite ceramic with an interconnected porous structure (IP-CHA)] and core decompression for spontaneous osteonecrosis of the femoral condyle in the knee

We employed a new surgical method for the treatment of spontaneous osteonecrosis of the medial femoral condyle of the knee joint. Twelve spontaneous osteonecrosis patients of Koshino's classification stage 2 or 3 underwent core decompression curettage with an artificial bone graft [hydroxyapatite ceramic with an interconnected porous structure (IP-CHA)]. The mean age at surgery was 69.6 years and the mean follow-up term was 24.6 months. All patients reported a decrease in knee pain, immediately after surgery. The Japanese Orthopaedic Association (JOA) scores of all the patients also improved post-surgery; X-ray and MR imaging indicated no worsening of the osteoarthritis, and smooth surfaces at the grafted areas of the artificial bone. No severe complications appeared in the patients. Our procedure was, therefore, less invasive and achieved results comparable to those involving traditional, more invasive methods. We recommend our novel procedure as a treatment for spontaneous osteonecrosis of the femoral condyle.     

Tibial plateau stress fracture after unicondylar knee arthroplasty using a navigation system: two case reports

Satisfactory alignments of components in total knee arthroplasty have been reported since the introduction of navigation systems. And thus, such techniques have been introduced for minimally invasive unicondylar knee arthroplasty (UKA). Several intraoperative fractures of the tibial plateau have been reported in association with minimally invasive UKA and some stress fractures of tibial plateau associated with design of instrument have been reported. Here, we report on two cases of stress fracture of the tibial medial plateau after minimally invasive UKA was performed using a navigation system.     

Prayer's fracture: rare cases of knee insufficiency fracture in non-weight-bearing femoral condyle

Insufficiency fractures are a relatively common sub-type of stress fractures and occur as a result of decreased bone resistance due to underlying conditions such as osteoporosis. Insufficiency fractures of the knee most commonly occur at the central weight-bearing zone of the medial femoral condyle. We present five unusual cases of insufficiency fractures occurring at the posterior non-weight-bearing zone of condyles. After investigating commonalities between these patients, we discovered that all of these patients performed the daily practice of prayer rituals that include high knee flexion. We have chosen to coin this type of fracture a “Prayer's fracture”. Considering the mechanics of high knee flexion, transient changes in the weight-bearing zone of knee explain the unusual location of this fracture. We describe these cases, the characteristic imaging appearance, and the probable biomechanics that we believe predispose patients to this type of injury.     

Prayer's fracture: rare cases of knee insufficiency fracture in non-weight-bearing femoral condyle

Insufficiency fractures are a relatively common sub-type of stress fractures and occur as a result of decreased bone resistance due to underlying conditions such as osteoporosis. Insufficiency fractures of the knee most commonly occur at the central weight-bearing zone of the medial femoral condyle. We present five unusual cases of insufficiency fractures occurring at the posterior non-weight-bearing zone of condyles. After investigating commonalities between these patients, we discovered that all of these patients performed the daily practice of prayer rituals that include high knee flexion. We have chosen to coin this type of fracture a “Prayer's fracture”. Considering the mechanics of high knee flexion, transient changes in the weight-bearing zone of knee explain the unusual location of this fracture. We describe these cases, the characteristic imaging appearance, and the probable biomechanics that we believe predispose patients to this type of injury.     

The effect of posterior cruciate ligament deficiency on knee kinematics

BACKGROUND: Alteration of the kinematics of the PCL-deficient knee might be a factor in producing the articular damage. Very little is known about the in vivo weightbearing kinematics of the PCL-deficient knee. HYPOTHESIS: Isolated rupture of the posterior cruciate ligament alters knee kinematics, predisposing the patient to development of early osteoarthritis. STUDY DESIGN: Case series. METHODS: Tibiofemoral motion was assessed using open-access magnetic resonance imaging, weightbearing in a squat, through the arc of flexion from 0 degrees to 90 degrees in 6 patients with isolated rupture of the posterior cruciate ligament in one knee and a normal contralateral knee. Passive sagittal laxity was assessed by performing the posterior and anterior drawer tests while the knees were scanned, again using the same magnetic resonance imaging scanner. The tibiofemoral positions during this stress magnetic resonance imaging examination were measured from midmedial and midlateral sagittal images of the knees. RESULTS: Rupture of the posterior cruciate ligament leads to an increase in passive sagittal laxity in the medial compartment of the knee (P < .006). In the weightbearing scans, posterior cruciate ligament rupture alters the kinematics of the knee with persistent posterior subluxation of the medial tibia so that the femoral condyle rides up the anterior upslope of the medial tibial plateau. This fixed subluxation was observed throughout the extension-flexion arc and was statistically significant at all flexion angles (P < .018 at 0 degrees , P < .013 at 20 degrees , P < .014 at 45 degrees , P < .004 at 90 degrees ). The kinematics of the lateral compartment were not altered by posterior cruciate ligament rupture. The posterior drawer test showed increased laxity in the medial compartment. CONCLUSION: Posterior cruciate ligament rupture alters the kinematics of the medial compartment of the knee, resulting in "fixed" anterior subluxation of the medial femoral condyle (posterior subluxation of the medial tibial plateau). This study helps to explain the observation of increased incidence of osteoarthritis in the medial compartment, and specifically the femoral condyle, in posterior cruciate ligament-deficient knees.     

膝关节色素沉着绒毛结节性滑膜炎的影像学诊断

目的 探讨膝关节色素沉着绒毛结节性滑膜炎(PVNS)的影像学表现。方法 回顾分析9例经手术及病理证实的色素沉着绒毛结节性滑膜炎影像学资料并进行总结。9例膝关节病变均行MR检查，其中3例增强扫描；X线平片检查6例；CT平扫5例。结果 (1)X线表现：6例中关节间隙5例正常，1例增宽；股骨髁破坏1例；胫骨平台破坏4例；共9个病灶，其中7个病灶周围见硬化环。(2)CT表现：5例PVNS均显示关节腔积液；股骨髁合并胫骨平台破坏1例，胫骨平台单发或多发破坏4例，共12个病灶，所有病灶周围均见硬化环。2例合并胭窝内软组织密度肿块。(3)MRI表现：9例中弥漫型7例，局灶型2例。7例弥漫型PVNS均见关节腔积液，其中3例髌上囊积液中见低信号结节，3例前、后交叉韧带表面可见不规则增厚的低信号滑膜覆盖，6例伴有股骨髁或胫骨平台骨质破坏，共15个病灶，其中13个病灶周围绕以低信号硬化环。3例增强扫描显示增厚的滑膜和结节均明显强化。2例局灶型PVNS表现为单发性肿块伴关节腔积液。结论 膝关节色素沉着绒毛结节性滑膜炎的MRI表现较CT、X线表现具有特征性，能够作出正确诊断。     

Spontaneous osteonecrosis of the knee and medial meniscal tears

Several factors may play a role in the etiology of "spontaneous" osteonecrosis of the medial femoral condyle. Corticosteroids are known to induce osteonecrosis, and 45% of the patients in this study received steroids parenterally or by intra-articular injection. Another factor, heretofore given little attention, is the association of medial meniscal tears and "spontaneous" osteonecrosis. Twenty-one (78%) of 27 knees examined by arthrography demonstrated meniscal tears. Stress concentration over the edge of the meniscal fragment may result in ischemic necrosis of the femoral condyle. Early detection of a medial meniscal tear by arthrography in older patients and prompt treatment may be important in avoiding the late changes of "spontaneous" osteonecrosis.     

Subchondral insufficiency fracture of the femoral head and medial femoral condyle

This case report documents the clinical, radiographic, and histologic findings in a 69-year-old obese man, who had subchondral insufficiency fracture both in the femoral head and medial femoral condyle. On plain radiographs, both lesions underwent subchondral collapse. Magnetic resonance images of the left hip showed a bone marrow edema pattern with associated low-intensity band on T1-weighted images, which was convex to the articular surface. The histopathologic findings in the hip and knee were characterized by the presence of a subchondral fracture with associated callus and granulation tissue along both sides of a fracture line. There was no evidence of antecedent osteonecrosis. To our knowledge, this is the first case report to describe the multiple occurrence of collapsed subchondral insufficiency fracture. Received: 22 May 1999 Revision requested: 5 August 1999 Revision received: 13 September 1999 Accepted: 15 September 1999     

严重急性呼吸综合征康复者髋、膝关节骨坏死与激素治疗的关系

目的了解严重急性呼吸综合征（SARS）康复者下肢骨缺血与激素治疗的关系。资料与方法对来自广州市5所医院的148例SARS康复医务人员下肢骨包括双侧髋关节及膝关节进行MRI检查。148例中42例未使用激素治疗,106例使用不同剂量的激素治疗。MRI检查分为筛查与详查。筛查包括T1WI及短反转时间反转恢复序列（STIR）冠状位成像。筛查有阳性发现者则进行详查,在筛查的基础上加用横断位、冠状位T2WI及STIR成像。结果42例未使用激素治疗者未发现下肢骨坏死。106例使用激素治疗康复者中,共发现8例骨缺血改变,其中1例为双侧股骨头缺血坏死,2例为单侧股骨头缺血坏死,1例为双侧股骨头、胫骨髁及单侧股骨髁缺血坏死,1例单侧股骨髁缺血坏死,1例单侧股骨颈骨梗死并钙化,2例双侧股骨、胫骨骨髓水肿。多因素Logistic回归分析显示激素累积剂量是骨缺血性坏死最重要的危险因素（P=0．001）。结论使用激素治疗的SARS康复者中,少数发生下肢骨缺血坏死,而激素累积剂量与骨缺血性坏死关系密切。     

Spontaneous osteonecrosis of the knee Treatment and evolution

We performed a retrospective study on 21 patients affected by unilateral spontaneous osteonecrosis of the femoral condyle. Fifteen were women and 6 men. Their average age was 66.9 years. In ten cases the onset of pain was sudden, with a clear previous history of trauma in two of them. Gait pain, effusion, and joint locking were the most frequent clinical symptoms. At the time of diagnosis, 7 patients presented with grade I necrosis, 8 grade II, 1 grade III, and 5 grade IV, following Koshino’s classification [11]. The average percentage of osteonecrosis was 36.8%. Six patients underwent conservative treatment with physical exercises and nonsteroidal anti-inflammatory drugs. We performed arthroscopy alone in 4 patients, arthroscopy and drilling in 8, valgus high tibial osteotomy in 2, and total knee arthroplasty in 1. The overall results after an average follow-up of 41 months were excellent and good in 76.2% of the cases, fair in 14.3%, and poor in 9.5%. An associated medial meniscus tear was found in half of the patients who underwent surgery. In patients diagnosed with grade III and IV osteonecrosis, no increase in the percentage of necrosis was observed. Received: 10 May 1996 Accepted: 7 April 1997     

Prevalence of spontaneous osteonecrosis of the medial femoral condyle in elderly patients

Aseptic osteonecrosis of the medial femoral condyle has recently been reported as a complication of arthroscopic surgery. The time interval between the onset of symptoms and pathognomonic MRI changes (diagnostic window) is not known for osteonecrosis of the knee. To determine the prevalence of early-stage spontaneous osteonecrosis of the knee (SONK) we prospectively examined 176 patients by MRI between May 1998 and December 1999. In six patients MRI revealed a bone marrow edema pattern and subtle subchondral bone changes in the medial condyle consistent with early-stage SONK (prevalence of 3.4%); in the 53 patients older than 65 years the prevalence was 9.4%. In 10 patients (5.7%) the bone and marrow changes on MRI imaging either resolved on follow-up MRI and were regarded as transient epiphyseal lesions or were considered to be reactive changes due to underlying degenerative articular disease. Including MRI in the preoperative diagnostic procedures could avoid missing the diagnosis of avascular necrosis before planning an operative treatment of suspected meniscal tears in elderly patients.     

Spectrum of T2* values in knee joint cartilage at 3 T: a cross-sectional analysis in asymptomatic young adult volunteers

Objective

To establish baseline T2* values in healthy knee joint cartilage at 3 T.

Materials and Methods

Thirty-four volunteers (mean age: 24.6?±?2.7 years) with no history or clinical findings indicative of any knee joint disease were enrolled. The protocol included a double-echo steady-state (DESS) sequence for morphological cartilage evaluation and a gradient-echo multi-echo sequence for T2* assessment. Bulk and zonal T2* values were assessed in eight regions: posterior lateral femoral condyle; central lateral femoral condyle; trochlea; patella; lateral tibial plateau; posterior medial femoral condyle; central medial femoral condyle; and medial tibial plateau. Statistical evaluation comprised a two-tailed t test and a one-way analysis of variance to identify zonal and regional differences.

Results

T2* mapping revealed higher T2* values in the superficial zone in all regions (P values?≤?0.001) except for the posterior medial femur condyle (P?=?0.087), and substantial regional differences demonstrating superior values in trochlear cartilage, intermediate values in patellar and central femoral condylar cartilage, and low T2* values in posterior femoral condylar cartilage and tibial plateau cartilage.

Conclusion

Substantial regional differences in T2* measures should be taken into consideration when conducting T2* mapping of knee joint cartilage.