膝关节类风湿关节炎MRI与X线平片对比

目的　评价MRI与X线平片在膝关节类风湿关节炎中的诊断价值。方法　 34个膝关节行MRI与X线检查 ,13例进行了MRI增强扫描。结果　MRI显示 34个膝均存在骨破坏 ,2 1个膝骨硬化 ,2 2个半月板有信号改变 ,15个膝关节软骨信号改变 ,10个膝胫骨移位 ,8个膝后交叉韧带拉直 ,13例MRI增强扫描显示血管翳附着、滑膜增殖和关节积液。X线显示 1个膝有骨破坏 ,11个膝伴骨硬化 ,16个膝关节间隙狭窄 ,8个膝胫骨移位。结论　MRI诊断膝关节类风湿关节炎优于X线平片     

Subchondral bone infractions in acute ligamentous knee injuries demonstrated on bone scintigraphy and magnetic resonance imaging.

Bone scintigraphy is used to detect radiographically silent fractures. Magnetic resonance imaging (MRI) is currently used to screen knee injuries for cartilage and ligament damage. MRI also delineates bone marrow and fractures. We investigated the bone scintigraphic findings in patients who had subchondral bone injuries demonstrated on MRI. Thirteen patients underwent MRI, three-phase bone scintigraphy with SPECT, and arthroscopic surgery after sustaining acute traumatic hemarthrosis of a knee. They all had clinically unsuspected subchondral bone injuries demonstrated on MRI with normal radiographs and normal overlying articular cartilage at arthroscopy, consistent with occult fractures. All showed focal bone repair on scintigraphy. Two of the 13 patients showed additional bone injuries only on bone scan. Two other patients scintigraphically showed focal bone repair at the medial femoral condyle due to avulsion of the medial collateral ligament. SPECT was easier to interpret than multi-view planar imaging. Bone scintigraphy confirms subchondral fractures demonstrated on MRI but also demonstrates ligament avulsion injuries and additional more subtle bone injuries.     

血友病性关节病的MRI分析

目的:探讨血友病性关节病的MRI表现及临床价值.方法:回顾性分析11例22个膝关节血友病性关节病患者的MRI表现.结果:22个膝关节均有积血,表现为关节腔、骨骼和/或软组织血肿,早期血肿在T1WI为等信号、T2WI呈高信号;中期血肿在T1WI呈略高信号或混杂信号,T2WI呈高信号或混杂信号;晚期血肿在T1WI和T2WI均表现为混杂信号,血肿逐渐被吸收.病变早期关节结构基本保持正常,中晚期关节结构均有损害,表现为关节软骨、骨皮质破坏吸收,关节间隙狭窄,骨端或骨骺增大变形.早中期滑膜、关节囊、肌肉及韧带肿胀,而晚期则萎缩、退变.结论:MRI能准确显示血友病性关节病的病理改变,对疾病分期、指导临床治疗及同位素放射治疗效果评价具有重要意义.     

膝类风湿关节炎的MRI与病理对照研究

目的通过对膝类风湿关节炎(RA)病人关节软骨、软骨下骨髓及半月板进行MR-病理对照分析,探讨膝RA的MRI特点及病变发生机制。方法收集我院2008年11月—2014年12月间确诊为膝RA并行全膝关节置换术的11例病人(共13只膝关节)资料。评价关节软骨、软骨下骨髓及半月板的MRI表现,并在显微镜下对观察膝RA病人膝关节各部位组织的病理学特点。当细胞成分不确定时,使用免疫组织化学方法确定细胞种类。对关节软骨损伤MRI分级和半月板损伤MRI分度以及不同部位关节软骨下骨髓水肿和关节软骨、半月板损伤的病理学表现分度进行分析,并采用Mann-Whitney U检验对位于裸区和远离裸区的软骨下骨髓水肿的病理学表现分度进行比较。结果本组膝RA病人中大部分病人的MRI关节软骨破坏程度为4级,半月板破坏程度为4度。MRI显示52处软骨下骨髓水肿的部位中有18处(34.6%)于骨髓水肿上方覆盖有关节软骨且远离裸区,而34处(65.4%)的骨髓水肿位于裸区且邻近滑膜。在软骨下骨髓水肿的病理学表现中,纤维化、骨小梁镶嵌样结构及淋巴细胞浸润为最常见的表现。位于裸区和远离裸区骨髓水肿的两组间各种病理学表现分度差异均无统计学意义(均P0.05)。在关节软骨破坏的病理学表现中,纤维环、关节软骨破坏变薄及关节软骨增生为最常见的镜下病理表现。在全部13只切除的膝关节共26个半月板标本中,仅发现5个(19.2%)残留半月板标本,在MRI上均表现为萎缩、变薄,信号不均,其最常见的病理学表现为纤维化和吞噬包裹钙化碎片。结论晚期膝RA病人半月板及关节软骨破坏严重,骨髓水肿可发生于关节裸区或远离裸区部位,提示膝RA可同时累及多个部位,导致病人关节功能严重减退甚至丧失。     

Diagnostic performance of in vivo 3-T MRI for articular cartilage abnormalities in human osteoarthritic knees using histology as standard of reference

The purpose of this study was (1) to evaluate the sensitivity, specificity and accuracy of sagittal in vivo 3-T intermediate-weighted fast spin-echo (iwFSE) sequences in the assessment of knee cartilage pathologies using histology as the reference standard in patients undergoing total knee replacement, and (2) to correlate MR imaging findings typically associated with osteoarthritis such as bone marrow edema pattern (BMEP) and cartilage swelling with histological findings. Tibial plateaus and femoral condyles of eight knees of seven patients were resected during surgery, and sagittal histological sections were prepared for histology. Preoperative MRI findings were compared to the corresponding region in histological sections for thickness, surface integrity and signal pattern of cartilage, and histological findings in areas of BMEP and swelling were documented. The overall sensitivity, specificity and accuracy were 72%, 69% and 70% for thickness, 69%, 74% and 73% for surface and 36%, 62% and 45% for intracartilaginous signal pattern. For all cases of BMEP on MRI subchondral ingrowth of fibrovascular tissue and increased bone remodeling were observed. MRI using fat-saturated iwFSE sequences showed good performance in assessing cartilage thickness and surface lesions, while signal changes of cartilage were not suited to characterize the severity of cartilage degeneration as validated by histology.     

Subchondral bone marrow edema in patients with degeneration of the articular cartilage of the knee joint

PURPOSE: To retrospectively determine at magnetic resonance (MR) imaging the prevalence of subchondral bone marrow edema beneath arthroscopically proved articular cartilage defects. MATERIALS AND METHODS: The study was performed in compliance with HIPAA regulations, and a waiver of informed consent was obtained from the institutional review board before the study was performed. The study consisted of 132 patients (70 men, 62 women; average age, 53 years) with articular cartilage defects of the knee joint who underwent MR imaging of the knee and subsequent arthroscopic knee surgery. At the time of arthroscopy, each articular cartilage lesion was graded by using the Noyes classification system. MR examinations were retrospectively reviewed to determine the size, depth, and location of subchondral bone marrow edema without knowledge of the arthroscopic findings. Pairwise Fisher exact tests and two-sample t tests were used to correlate MR imaging findings of subchondral bone marrow edema with the arthroscopic grade of articular cartilage degeneration. RESULTS: Subchondral bone marrow edema was seen beneath 105 (19%) of 554 articular cartilage defects identified at arthroscopy. It was not observed beneath any of the six grade 1 cartilage defects but was observed beneath eight (4.9%) of 163 grade 2A defects, 40 (14.4%) of 278 grade 2B defects, 54 (55.1%) of 98 grade 3A defects, and three (33.3%) of nine grade 3B defects. Subchondral bone marrow edema was also seen beneath four (1.4%) of 238 articular surfaces that appeared normal at arthroscopy. The mean depth and cross-sectional area of subchondral bone marrow edema increased with increasing grade of the articular cartilage lesion. CONCLUSION: Higher grades of articular cartilage defects are associated with higher prevalence and greater depth and cross-sectional area of subchondral bone marrow edema.     

Treatable chondral injuries in the knee: frequency of associated focal subchondral edema

OBJECTIVE: In the knee, chondral flaps and fractures are radiographically occult articular cartilage injuries that can mimic meniscal tears clinically; once correctly diagnosed, these injuries can be treated surgically. We investigated an associated MR imaging finding--focal subchondral bone edema--in a series of surgically proven lesions. MATERIALS AND METHODS: Two musculoskeletal radiologists retrospectively reviewed the MR studies of 18 knees with arthroscopically proven treatable cartilage infractions, noting articular surface defects and associated subchondral bone edema; subchondral edema was defined as focal regions of high signal intensity in the bone immediately underlying an articular surface defect on a T2-weighted or short inversion time inversion recovery (STIR) image. RESULTS: The first observer saw focal subchondral edema deep relative to a cartilage surface defect in 15 (83%) of the 18 cases; in two additional cases a surface defect was seen without underlying edema. The second observer identified 13 knees (72%) with surface defects and associated subchondral edema and three with chondral surface defects and no associated edema. Subchondral edema was seen more frequently on fat-suppressed images and on STIR images than non-fat-suppressed images. CONCLUSION: Focal subchondral edema is commonly visible on MR images of treatable, traumatic cartilage defects in the knee; this MR finding may prove to be an important clue to assist in the detection of these traumatic chondral lesions.     

A capsular incision leads to a fast osteoarthritic response, but also elevated levels of activated osteogenic protein-1 in rabbit knee joint cartilage

We studied whether a small capsular incision alone, or combined with meniscectomy could induce early osteoarthritic changes in the rabbit knee. Thirty-one rabbits were operated on with a capsular incision in the left knee and meniscectomy in the right knee. Another 12 rabbits were used as controls. The rabbits were killed 3, 6 and 12 weeks after surgery. Osteoarthritic changes in the articular cartilage were evaluated by the modified Mankin score. The subchondral bone was evaluated by scintimetry ((99m)Tc-HDP) and semiquantitative grading of histological changes. Osteogenic protein (OP-1) in its mature and pro-form was examined by immunohistochemistry. Both a capsular incision and meniscectomy induced articular cartilage fibrillation and increased bone metabolic activity during the initial weeks after surgery. Capsular incision led to lesser changes than meniscectomy. Mature OP-1 was elevated, and its pro-form reduced, in meniscectomized knees. A similar pattern was observed in knees with capsular incision. Already 3 weeks after surgery, the articular cartilage and subchondral bone showed typical signs of early osteoarthritis (OA), and a reparative response was suggested by increased intensity of OP-1 staining. As these signs were also found in knees with capsular incision only, it appears that trauma-related factors such as increased bleeding and inflammation are critical for the development of OA.     

MRI demonstration of hypertrophic articular cartilage repair in osteoarthritis

Transection of the anterior cruciate ligament in the dog produces changes in the unstable joint typical of osteoarthritis, although full-thickness cartilage ulceration is rare. Information concerning the late fate of the cartilage after transection is meager. In the present study magnetic resonance imaging (MRI) was used to evaluate cartilage abnormalities 3 years after transection. Plain radiographs of the osteoarthritic and contralateral knees were obtained serially. MRI was performed 3 years after anterior cruciate ligament transection, at which time all three animals exhibited knee instability. Radiographs of the osteoarthritic knees showed osteophytes and subchondral sclerosis with progression between 2 and 3 years. On MRI, articular cartilage margins in the knee were indistinct, and the cartilage was thicker than that in the contralateral knee (maximum difference= 2.7 mm). This increase in thickness is consistent with biochemical data from dogs killed up to 64 weeks after creation of knee instability, which showed marked increases in cartilage bulk and in proteoglycan synthesis and concentration. The findings emphasize that increased matrix synthesis after anterior cruciate ligament transection leads to functional cartilage repair sustained even in the presence of persistent alteration of joint mechanics.     

An efficient subset of morphological measures for articular cartilage in the healthy and diseased human knee

The relationship between three‐dimensional, MRI‐based morphologic measurements commonly taken of knee cartilage was examined to determine whether a subset of variables fully reflects differences observed in cartilage in cross‐sectional and longitudinal studies. The benefits of a subset of measures include increased statistical power due to reduced multiple comparisons, improved understanding of relationships between the morphologic measures of articular knee cartilage, and greater efficiency in reporting results. One hundred fifty‐two women (77 healthy and 75 with knee osteoarthritis) had coronal 3‐T MR images of the knee acquired at baseline and at 24 months. Measures of femorotibial cartilage morphology (surface area, thickness, volume, etc.) were determined in the medial and lateral tibia and femur. Cartilage thickness (mean cartilage thickness over the total area of the [subchondral] bone), total subchondral bone area, and percentage of denuded area of the subchondral bone were found to explain over 90% of the cross‐sectional and longitudinal variation observed in other measures of cartilage morphology commonly reported in knee osteoarthritis. Hence, these three measures of cartilage morphology explain nearly all variation in a larger set of common cartilage morphology measures both cross‐sectionally and longitudinally, both in healthy and in osteoarthritic knees. These variables hence define an efficient subset for describing structural status and change in osteoarthritic cartilage. Magn Reson Med 63:680–690, 2010. © 2010 Wiley‐Liss, Inc.     

MRI对急性膝关节软骨损伤的评价

目的 分析急性膝关节软骨损伤的MRI表现，以达到准确评价关节软骨损伤的范围及程度。方法 分析34例在15d内有膝关节损伤病史，且经关节镜和手术证实为关节软骨损伤患者的膝关节MRI所见，着重观察关节软骨和软骨下骨的改变，并与关节镜和手术结果对照分析。结果 34例急性损伤膝关节中有29例在MRI上表现异常，其中软骨信号异常改变4例，软骨局限性变薄3例，骨软骨压迹3例，软骨凹凸不平(皱褶)3例，软骨连续性中断13例，软骨缺损2例，软骨缺损伴关节内游离软骨体1例。MRI还发现关节镜无法观察到的骨挫伤、隐匿性骨折等改变。结论 MRI对急性关节软骨损伤的显示准确，MRI结合关节镜检查可准确评价急性膝关节损伤的范围、程度，可决定治疗方案.     

MRI appearance of chondral delamination injuries of the knee

OBJECTIVE: We describe the MRI appearance of five cases of chondral delamination of the knee. CONCLUSION: Chondral delamination injuries of the knee show increased linear signal abnormality at the junction of the articular cartilage and subchondral bone on T2-weighted (fast spin-echo) images of the knee. Identifying and treating these lesions results in an improved prognosis for patients with this injury.     

Knee in early juvenile rheumatoid arthritis: MR imaging findings

PURPOSE: To determine the magnetic resonance (MR) imaging findings in the knee in early juvenile rheumatoid arthritis. MATERIALS AND METHODS: MR imaging (1.5 T) was performed in the more symptomatic knee in 30 children with juvenile rheumatoid arthritis with a symptom duration 1 year or less. Conventional, fast spin-echo, three-dimensional gradient-echo, and gadolinium-enhanced T1-weighted images were assessed. Two radiologists independently read the images, and a third resolved disagreements. These images were compared with knee radiographs in 27 children. RESULTS: Mean maximal synovial thickness was 4.8 mm +/- 2.4 (SD). Mean synovial volume was 15.4 mL +/- 10.8. Suprapatellar joint effusions were seen in 26 (87%) of 30 knees, meniscal hypoplasia in 11 (37%) of 30 knees, and abnormal epiphyseal marrow in eight (27%) of 30 knees. Three knees had articular cartilage contour irregularity, fissures, and/or thinning. One knee had a bone erosion. Knee radiographs showed suprapatellar fullness in 78% of the knees, joint space narrowing in one knee, and no bone abnormalities. CONCLUSION: Synovial hypertrophy and joint effusions are the most frequent MR imaging findings of knees in early juvenile rheumatoid arthritis. Early in the disease, radiographically occult cartilage and bone erosions are uncommonly seen at MR imaging. The potential relationship of synovitis to cartilage abnormalities deserves further study.     

Correlation between radiographic findings of osteoarthritis and arthroscopic findings of articular cartilage degeneration within the patellofemoral joint

Objectives To correlate radiographic findings of osteoarthritis on axial knee radiographs with arthroscopic findings of articular cartilage degeneration within the patellofemoral joint in patients with chronic knee pain.Subjects and methods The study group consisted of 104 patients with osteoarthritis of the patellofemoral joint and 30 patients of similar age with no osteoarthritis of the patellofemoral joint. All patients in the study group had an axial radiograph of the knee performed prior to arthroscopic knee surgery. At the time of arthroscopy, each articular surface of the patellofemoral joint was graded using the Noyes classification system. Two radiologists retrospectively reviewed the knee radiographs to determine the presence of marginal osteophytes, joint-space narrowing, subchondral sclerosis, and subchondral cysts. The sensitivity and specificity of the various radiographic features of osteoarthritis for the detection of articular cartilage degeneration within the patellofemoral joint were determined.Results The sensitivity of marginal osteophytes, joint-space narrowing, subchondral sclerosis, and subchondral cysts for the detection of articular cartilage degeneration within the patellofemoral joint was 73%, 37%, 4%, and 0% respectively. The specificity of marginal osteophytes, joint-space narrowing, subchondral sclerosis, and subchondral cysts for the detection of articular cartilage degeneration within the patellofemoral joint was 67%, 90%, 100%, and 100% respectively.Conclusion Marginal osteophytes were the most sensitive radiographic feature for the detection of articular cartilage degeneration within the patellofemoral joint. Joint-space narrowing, subchondral sclerosis, and subchondral cysts were insensitive radiographic features of osteoarthritis, and rarely occurred in the absence of associated osteophyte formation.     

Osteochondral autograft transplantation in the porcine knee

BACKGROUND: Knee articular cartilage defects are not an uncommon problem. Because articular cartilage is limited in its ability to heal, these defects are difficult to manage. HYPOTHESIS: Osteochondral autografts will provide less of a cavitary defect and more viable hyaline articular cartilage than will control knees. STUDY DESIGN: Controlled laboratory study. METHODS: Osteochondral autografts were grossly and microscopically evaluated in the porcine knee and compared with a control at 6 weeks, 3 months, and 6 months. In 18 porcine specimens, a 1-stage surgical procedure was performed to harvest an osteochondral graft from a nonweightbearing articular cartilage surface, and the graft was transplanted into a defect created in the weight-bearing region of the medial femoral condyle. In the opposite control knee, a similar defect was created in the medial femoral condyle; an osteochondral transplant was not performed. Six pigs each were sacrificed at 6 weeks, 3 months, and 6 months. RESULTS: Gross inspection of the control knees showed a cavitary defect. The defect grossly decreased in size with fibrous ingrowth seen on microscopic analysis. An increasing amount of fibrous tissue and fibrocartilage was present at the 3 time periods. Gross inspection of the graft knee showed a healed osteochondral plug with no obvious displacement, cavitary defects, or surrounding necrotic tissue at each time interval. Microscopic analysis revealed the graft knee contained viable hyaline cartilage and healed viable subchondral bone. At all time intervals, 75% to 100% of the hyaline cartilage was viable in all specimens. In 6-month specimens, bridging cartilage at the autograft-host junction was incomplete in 50%, partial in 33%, and complete in 17%. CONCLUSION: Osteochondral autografts in the porcine knee resulted in viable hyaline cartilage for up to 6 months; there was inconsistent bridging hyaline cartilage at the periphery. Grafts appeared to heal into existing subchondral bone without displacement or evidence of necrosis. CLINICAL RELEVANCE: This type of osteochondral transplant can be used as a reliable reconstructive alternative for osteochondral defects.     

移植基质诱导的自体软骨细胞修复关节软骨缺损临床研究

 目的 探讨基质诱导的自体软骨细胞移植修复关节软骨缺损的方法与疗效.方法 2004年11月～2006年11月,对7例膝关节软骨炎患者行关节镜取软骨、基质诱导自体软骨细胞移植(Matrix-induced Autologous chondrocyte implantation,MACI)膜植入术.对患者行MRI检查确定损伤位置,并进行IKDC2000评分.术后按照特定的康复计划进行循序渐进的功能锻炼.结果 随访时间6个月到24个月.术后半年多数患者各项症状逐渐消失,IKDC2000评分大部分增高.复查MRI和关节镜,显示原来缺损的关节软骨已基本修复,并伴有软骨下骨的修复.结论 与传统自体软骨细胞移植(Autologous chondrocyte implantation,ACI)技术相比,利用MACI技术修复软骨缺损具有术后恢复时间短、操作简便、创伤小、生成更多透明软骨等优点,具有良好的应用前景.     

1.5-T surface-coil MRI of the knee

Five normal knees and 20 knees with suspected abnormalities involving the menisci or articular surfaces were examined with high-resolution surface-coil MRI. Surgical correlation was available in 15 cases. Signal-to-noise ratios were optimized using a field strength of 1.5 T and a round 7.6-cm surface coil. Spatial resolution was maximized by using fields of view reduced to as small as 8 cm. Separate examinations of the medial and lateral joint compartments were performed with the surface coil positioned vertically adjacent to the meniscus of interest. Ten meniscal tears were identified using sagittal and coronal images. T1-weighted images were adequate to detect most meniscal tears, and T2-weighted images were useful for providing an "arthrogram effect" in the presence of a joint effusion. Extrameniscal lesions that were examined included osteonecrosis of the femoral condyle, subchondral cysts, rheumatoid arthritis, degenerative arthritis, and anterior cruciate ligament tears. MRI was useful in determining the integrity of articular cartilage overlying defects in the subchondral bone and in detecting gross cartilage lesions in arthritis, but was less sensitive than arthroscopy in evaluating moderate changes in the hyaline cartilage.     

Evaluation of the articular cartilage of the knee joint with vastly undersampled isotropic projection reconstruction steady-state free precession imaging

PURPOSE: To determine the feasibility of the vastly undersampled isotropic projection reconstruction steady-state free precession (VIPR-SSFP) sequence for evaluating the articular cartilage of the knee joint. MATERIALS AND METHODS: A magnetic resonance (MR) examination of the knee was performed on 33 subjects using a GE 1.5T scanner and a phased-array extremity coil. VIPR-SSFP, proton density-weighted fast spin-echo (PD-FSE), fat-suppressed T2-weighted fast spin-echo (T2-FSE), and three-dimensional fat-suppressed spoiled gradient recall-echo (SPGR) sequences were performed on three asymptomatic volunteers and 10 patients with osteoarthritis of the knee joint. Signal-to-noise efficiency, and contrast-to-noise ratio (CNR) measurements were calculated for all sequences and compared with the use of paired t-tests. The VIPR-SSFP sequence was then performed on 20 consecutive patients who were undergoing a routine MR examination of the knee. RESULTS: The cartilage signal-to-noise efficiency of the VIPR-SSFP sequence was not significantly different from that of the PD-FSE and SPGR sequences. The cartilage signal-to-noise efficiency of the VIPR-SSFP sequence was significantly higher (P < 0.05) than that of the T2-FSE sequence. The VIPR-SSFP sequence produced images with significantly higher (P < 0.05) CNR between cartilage and synovial fluid than the PD-FSE and SPGR sequences, and significantly higher (P < 0.05) CNR between cartilage and subchondral bone than the T2-FSE sequence. The VIPR-SSFP sequence allowed excellent visualization of the articular cartilage of the knee joint in all subjects. All articular cartilage defects identified on the PD-FSE, T2-FSE, and SPGR images were well visualized on the VIPR-SSFP images. CONCLUSION: VIPR-SSFP images had high cartilage signal-to-noise efficiency and high CNR between cartilage and adjacent synovial fluid and subchondral bone; therefore, the sequence is well suited for evaluating the articular cartilage of the knee joint.     

MR cartilage imaging in assessment of the regenerative power of autologous peripheral blood stem cell injection in knee osteoarthritis

Background

Osteoarthritis (OA) describes an age-related, heterogeneous group of disorders characterized pathologically by focal areas of loss of articular cartilage in synovial joints, associated with varying degrees of osteophyte formation, subchondral bone change, and synovitis. Currently, cartilage repair remains a major challenge for physicians, being avascular with limited regenerative capacity. Stem cell therapy opened new horizons for hyaline cartilage repair. Peripheral blood stem cells (PBSC) due to their multi-lineage potential, immunosuppressive activities, and limited immunogenicity, were tried as an intra articular injection.

Aim of study

To find out the regenerative effect of repeated intra articular injections of autologous PBSC in knee joints of OA patients using MR cartilage imaging.

Methods

10 patients (3 males and 7 females) diagnosed with bilateral knee joints OA were included in this study, they underwent history taking, clinical examination and MR cartilage imaging using the semi-quantitative whole joint assessment score of knee for OA (MOAKS). Three intra articular injections of 8 ml of autologous PBSC in each knee were administered. Clinical and MRI assessments were repeated after 1 year.

Results

A significant reduction was seen in all parameters post injection. MR images analysis showed increased cartilage thickness in 65 knee joint compartments out of 160 affected compartments.

Conclusion

Limited good level of evidence showed that repeated intra-articular injections of autologous PBSC resulted in an improvement of the quality of articular cartilage repair and physical function as observed by MRI and clinical assessment.