Lipid composition of the tissues of human knee joints. II. Synovial fluid in trauma

Synovial fluid was aspirated from the knees of 125 patients and lipid profiles were determined. The patients had knee injuries with or without fracture of bone; these lipid profiles were compared with "controls" (synovial fluid obtained at surgery from patients that did not have a knee injury). Floating lipid droplets were observed in some of the synovial fluid from patients with fractures. These lipid droplets could be separated as a well-defined supernatant layer after a few minutes of centrifugation (100 X g). This layer was found to consist mostly of triglycerides. The synovial fluid from patients with fracture and those with only soft-tissue trauma showed increases in total lipids and triglyceride content but had lower phospholipids when compared with nontraumatized knees. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, sphingomyelin, cholesterol, monoglycerides, diglycerides, triglycerides, and free fatty acids were present in all synovial fluids assayed. The large amount of triglycerides in the synovial fluid in many cases may be a good indicator of marrow leakage. Because the soft tissue surrounding the knee is also rich in triglycerides, a low phospholipid level in some cases may be an even better indicator of marrow leakage.     

Synovial lining macrophages mediate osteophyte formation during experimental osteoarthritis

OBJECTIVE: In human osteoarthritis (OA), various forms of pathology are observed. Besides cartilage damage and fibrosis, neogenesis of bone, osteophyte formation, also occurs. Osteophytes are thought to limit joint movement and cause pain. The objective of this study was to investigate whether synovial macrophages are involved in osteophyte formation in experimental OA, and if they are, to study which mechanism may be involved. DESIGN: Experimental OA was induced by two intra-articular injections of collagenase on alternate days into murine knee joints. The role of synovial lining macrophages in this model was studied by selective removal of these cells prior to OA induction using clodronate liposomes. After 1 and 2 weeks, knee joints were dissected and examined (immuno)histologically. RESULTS: At days 7 and 14 after induction of OA, osteophyte formation and fibrosis were observed. Depletion of synovial macrophages resulted in spectacular reduction of osteophyte formation, 84% and 66%, respectively, at days 7 and 14. Fibrosis and synovial activation, measured by MRP8/14 expression, were also ameliorated (40-60%). In addition, production of growth factors (TGFbeta, BMP-2 and BMP-4) in the lining was largely prevented but production of these growth factors in deeper layers of the synovium and the periosteum did not differ from controls. CONCLUSIONS: These results indicate the synovial macrophage to be a pivotal cell in the synovium mediating osteophyte formation and other OA-related pathology, like fibrosis, during experimental OA. Production of growth factors and induction of synovial activation by these cells may play a crucial role in this event.     

Microstructural and histomorphological features of osteophytes in late-stage human knee osteoarthritis with varus deformity

ObjectivesTo illustrate the microstructural and histomorphological characteristics of osteophytes in the human knee osteoarthritis (OA).MethodsTibial plateau specimens, including osteophytes and subchondral trabecular bone (STB) from weight-bearing and non-weight-bearing regions, were obtained from 81 patients with OA after total knee arthroplasty surgery. All the patients had varus deformity of the knee. Micro-CT was applied to evaluate the microstructure characteristics of the tibial plateau, which was segmented into 6 regions of interest (ROIs). After micro-CT scanning, decalcified and undecalcified bone histology were performed to assess histological features and bone remodeling status in these different ROIs.ResultsIn both medial and lateral plateaus, osteophytes exhibited a less sclerotic microstructure and higher bone remodeling level compared with STB from weight-bearing and non-weight-bearing regions. Moreover, the medial osteophyte tended to have a more sclerotic microarchitecture and a relatively low level of bone metabolism than its lateral counterpart. Osteophyte, which consists of mesenchymal connective tissue cap, cartilage and mineralized bone tissue, demonstrated evident chondrocyte hypertrophy and endochondral ossification in the cartilage-to-bone interface. Compared with the non-weight-bearing region, the weight-bearing region showed more severely deteriorated cartilage, and more sclerotic subchondral bone with high remodeling status.ConclusionOsteophytes exhibited a sparse microstructure and high bone remodeling level in knee OA, but demonstrating region-dependent variations. In addition, the microstructure, bone metabolism status and pathological alterations of osteochondral complex were distinct between weight-bearing and non-weight-bearing regions in the tibial plateau. Biomechanical stress might play a pivotal role in osteophyte formation and deterioration of osteochondral complex.     

超声观察英夫利西单抗治疗强直性脊柱炎患者骨质改变的研究

目的 应用超声观察英夫利西单抗治疗前、后强直性脊柱炎患者骨质改变的情况,并探讨其临床意义。方法 48例活动性AS患者均满足1984年改良的纽约分类标准,并签署知情同意书,所有患者均接受6次infliximab 5 mg/kg 静脉输注。用高分辨率B超和能量型多普勒超声观察英夫利西单抗治疗前、后下肢关节及肌腱附着点的骨质形态学及血流供应的变化。并分别在0和30w记录背痛VAS评分,关节肿痛及CRP、ESR和BASDAI、BASFI、BASMI等指标。结果 48例AS患者完成试验,其中31例复查了超声检查。治疗前48例患者超声检查发现骨侵蚀有37处,骨赘有2处,肌腱增厚有17处,滑囊炎有15处,肌腱钙化1处,异常血流数有22处,关节积液11处,滑膜增生1处。英夫利西单抗治疗后30w,31例患者复查超声发现骨侵蚀8处,多普勒异常血流1处,与治疗前比较统计学有显著差异（P<0.01）,滑囊炎3处,与治疗前比较统计学有差异（P<0.05）。骨侵蚀中以股骨大转子肌腱点最多,有13处,治疗后只有2处;膝关节内侧副韧带有7处,治疗后为2处,与治疗前相比有统计学差异（P<0.05）。骨赘治疗前有2处,治疗后无进展,仍为2处,与治疗前相比无统计学差异（P>0.05）。治疗前后各临床指标均有明显好转,统计学有显著差异（P<0.01）。结论 超声可清晰显示肌腱附着点及关节的骨侵蚀、骨赘形成,并可发现肌腱增厚、滑囊炎、关节滑膜增生及异常血流等情况,能更实时反映AS患者骨质改变的过程及监测疗效。     

Asporin and knee osteoarthritis in patients of Greek origin

Ostearthritis (OA) is characterized by focal areas of loss of the articular cartilage in synovial joints, associated with varying degrees of osteophyte formation, subchondral bone change and synovitis. The Asporin (ASPN) gene which encodes a protein of the extracellular cartilage matrix contains a triplet repeat encoding for aspartic acid (D) within exon 2 The D14 allele was found associated with knee and hip osteoarthritis in case-control study in the Japanese population. Genotyping Greek knee OA patients for the D repeats we determined that the D15 allele could be considered a risk allele for our population.     

Free synovium grafting for the repair of the avascular portion of canine knee joint meniscus]

To evaluate the effect of free synovium on repair of avascular portion of the meniscus in the knee, two round full-thickness defects of 2 mm phi were made in the medial menisci of 57 dogs, followed by transplantation of free synovium or blood clots in the holes. Defects with no grafting served as control. Specimens were evaluated histologically at intervals from 1 day to 12 weeks after grafting. The portions of the medial menisci filled with blood clots gradually retracted after surgery and showed no complete repair 6 and 12 weeks after the operation as in the control. In the group which received synovial graft, however, fibrous reparation was observed in 62% of total 13 defects 3 weeks after grafting. Six and 12 weeks after the synovial transplantation, complete reparation by fibrocartilaginous tissue with no signs of tissue retraction was observed in more than 65% of total 17 defects. Therefore, synovial grafting seemed to be a potential method for the repair of the avascular portion of the canine knee joint meniscus.     

The natural course of osteoarthritis of the hip. Indication of conservative treatment in relation to osteophyte formation at the acetabular rim

One hundred and eighty-five hips from 152 patients with primary or secondary osteoarthritis were studied in an attempt to assess the degrees of hip pain in contrast to radiological and other clinical findings. In 30.8% and 26.4% of the primary and secondary osteoarthritic hips respectively, hip pain showed some gradual decrease as time elapsed. Pain relief probably in association with osteophyte formation at the craniolateral acetabular rim occurred in 62.5% and 33.3% of the primary and secondary osteoarthritic hips respectively. Significant parameters observed in the primary osteoarthritic cases of the decreasing pain group were as follows: A lesser extent of cranial displacement of the femoral head, poor capital drop development, well developed floor osteophyte. On the other hand significant parameters in the decreasing pain group of secondary osteoarthritis were as follows: Well developed floor osteophyte, a small size of cyst in both the femoral head and the acetabulum, few "b" or "d" type of bony sclerosis in the acetabulum. Careful observation of radiographic changes (cyst and sourcil) would be most important, especially in secondary osteoarthritis, to decide the indication of surgery. On the basis of histological studies of osteophyte at the craniolateral acetabular rim obtained at the operation, it was assumed that the osteophyte formation had initiated from metaplasia of the labrum or synovial membrane and progressed by a form of chondral ossification after the process of fibrous tissue formation. A well developed trabecular density in the osteophyte at the craniolateral acetabular rim was determined by the use of Muto digigrammer system, Model G-002.     

Early joint tissue changes are highly correlated with a set of inflammatory and degradative synovial biomarkers after ACL autograft and its sham surgery in an ovine model

While impossible in humans, the mechanisms of early cartilage, bone and meniscal damage can be quantified after anterior cruciate ligament (ACL) injury in animal models. We utilized an ovine model to determine if the mRNA expression of inflammatory and degradative molecules (IL‐1β, IL‐6, MMP‐1, 2, 3, and 13) in the synovium correlated to changes in joint tissues 2 weeks post‐ACL surgery, to test the hypothesis that synovial inflammation is a marker of these changes and possibly their originator. Nine “idealized” ACL autografts were performed and compared with three sham and six normal animals. Using validated protocols, early osteophyte formation, articular cartilage, and meniscal damage were quantified. Synovium was harvested and mRNA expression quantified using qPCR. Multiple linear regression analysis (MLRA) was utilized to correlate synovial mRNA expression in treated and contra‐lateral limbs, from all treatment groups with corresponding joint scores. Synovial mRNA expression was significantly elevated in all experimental and sham joints. The MLRA model was a significant predictive tool (p = 0.001, R² = 0.70) of gross tissue scores with significant contributions from IL‐1β, IL‐6, and MMP‐3. Findings suggest that this set of synovial biomarkers is predictive (p < 0.009) of early gross changes of joint tissues after arthrotomy and likely directly involved in the relevant mechanisms, particularly early osteophyte formation, in vivo. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1185–1192, 2011     

Specific mechanism of the knee joint preventing tumor invasion

Tumor extension from the anterior aspect of the distal femur into the knee joint was examined histologically and with MRI in 10 patients with primary malignancy of bone. Histologically, 1 tumor had invaded the joint with destruction of the transitional area between the articular cartilage and bone. In another case, the transitional area had been destroyed by mechanical traction of the periosteum by the tumor without invasion. The fatty connective tissue and superficial synovial layer were detached from the femoral cortex and elevated upwards by tumor growth without destruction in 7 tumors but were unchanged in 3 tumors. Tl-weighted MRI clearly revealed high signal intensity of the connective tissue and synovium in the 7 tumors with elevation. The average elevation of this detachment of the fatty connective tissue and synovium from the femoral cortex calculated from MR images was 12 mm. Destruction of the transitional area between the articular cartilage and bone was detected in 2 tumors on Tl-weighted MR images. Our results indicate that fatty connective tissue and the superficial synovial layer are easily detached and elevated by tumors. This mechanism probably prevents tumor extension into the joint space.     

99mTc-DPD uptake in juvenile hemarthrosis. Scintimetry and autoradiography of the knee in dogs

The pathogenesis of subchondral bone lesions and growth plate affection in hemophilic arthropathy was studied in puppies by means of repeated regional 99mTc-diphosphonate scintimetry and contact autoradiography. Unilateral hemarthrosis of the knee was induced by biweekly intraarticular injections of autologous blood for 12 weeks. Hemarthrosis caused an early (2 to 4 weeks) decrease in uptake of 99mTc-diphosphonate in the juxtaarticular growth plates (ratio 0.7) and a delayed (8 to 10 weeks) increase in epiphyseal uptake (ratio 1.5). In a recovery phase after hemarthrosis, growth plate uptake returned to normal, while the epiphyseal uptake remained elevated for 8 to 10 weeks. By contact autoradiography, the growth plate uptake was localized to the calcification layer at the metaphyseal aspect of the growth plates, while the epiphyseal uptake mainly was seen in the thin subchondral and subsynovial bone layer and around osteophytes. The changes in uptake of 99mTc-diphosphonate following hemarthrosis for 3 months were reversible and could be ascribed to the presence of synovial inflammation.     

Poor outcome after a surgically treated chondral injury on the medial femoral condyle: early evaluation with dGEMRIC and 17-year radiographic and clinical follow-up in 16 knees

Background and purpose — The optimal treatment for traumatic cartilage injuries remains unknown. Contrast-enhanced MRI of cartilage (dGEMRIC) evaluates cartilage quality and a low dGEMRIC index may predict radiographic osteoarthritis (OA). The purpose of this study was (a) to explore the results 17 years after surgical treatment of an isolated cartilage knee injury and (b) to evaluate the predictive value of dGEMRIC.

Patients and methods — 16 knees with an isolated traumatic cartilage injury of the medial femoral condyle had cartilage repair surgery either by microfracture or autologous cartilage implantation. dGEMRIC of the injured knee was performed 2 years after surgery and radiographic examinations were performed 17 years after the operation.

Results — Radiographic OA was present in 12 of 16 knees. Irrespective of surgical method, the dGEMRIC index was lower in repair tissue compared with adjacent cartilage in the medial compartment, 237?ms vs. 312?ms (p < 0.001), which in turn had lower value than in the non-injured lateral cartilage, 312?ms vs. 354?ms (p < 0.008). The dGEMRIC index in the cartilage adjacent to the repair tissue correlated negatively with radiographic osteophyte score, r = –0.75 (p = 0.03).

Interpretation — A traumatic cartilage injury is associated with a high prevalence of OA after 17 years. The low dGEMRIC index in the repair tissue 2 years postoperatively indicates fibrocartilage of low quality. The negative correlation between the dGEMRIC index in the adjacent cartilage and future OA suggests that the quality of the surrounding cartilage influences outcome after cartilage repair surgery.     

Haemodynamics in acute arthritis of the knee in puppies

In order to study the haemodynamic changes of the juvenile knee in acute arthritis, an experimental model was developed in puppies by unilateral intra-articular injections of Carragheenin solution into the knee. Tissue blood flow was studied by the tracer microsphere technique in eight dogs and simultaneous intra-articular and intraosseous pressure recordings were performed in seven other dogs. The intra-articular pressure was elevated in all arthritic knees. Hyperaemia was found in the knee-joint capsule and distal femoral metaphysis, whereas juxta-articular epiphyseal blood flow rates were not significantly changed. A decrease of femoral muscle blood flow was encountered. Intraosseous pressure recordings during venous tamponade of the knee-joint capsules suggested a qualitative change of bone vasculature in acute arthritis. The juxta-articular bone blood flow in arthritis appears to be influenced by synovial hyperaemia, synovial effusion pressure, an "inflammatory resistance factor" and the anatomical relationship of the epiphyseal vessels to the knee-joint capsule.     

Comparison of loading rate‐dependent injury modes in a murine model of post‐traumatic osteoarthritis

Post‐traumatic osteoarthritis (PTOA) is a common long‐term consequence of joint injuries such as anterior cruciate ligament (ACL) rupture. In this study we used a tibial compression overload mouse model to compare knee injury induced at low speed (1 mm/s), which creates an avulsion fracture, to injury induced at high speed (500 mm/s), which induces midsubstance tear of the ACL. Mice were sacrificed at 0 days, 10 days, 12 weeks, or 16 weeks post‐injury, and joints were analyzed with micro‐computed tomography, whole joint histology, and biomechanical laxity testing. Knee injury with both injury modes caused considerable trabecular bone loss by 10 days post‐injury, with the Low Speed Injury group (avulsion) exhibiting a greater amount of bone loss than the High Speed Injury group (midsubstance tear). Immediately after injury, both injury modes resulted in greater than twofold increases in total AP joint laxity relative to control knees. By 12 and 16 weeks post‐injury, total AP laxity was restored to uninjured control values, possibly due to knee stabilization via osteophyte formation. This model presents an opportunity to explore fundamental questions regarding the role of bone turnover in PTOA, and the findings of this study support a biomechanical mechanism of osteophyte formation following injury. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:79–88, 2014.     

Inflammatorische Reaktion auf Abriebpartikel von Endoprothesen in vivo

Although it is now widely recognized that the inflammatory response to implant wear particles plays an important role in aseptic loosening of total joint replacements, the precise mechanisms of this process remain unclear. The aim of this study was to establish an animal model for the study of the adverse response to particulate wear debris and the effects on the synovial microcirculation as well as the leukocyte-endothelial cell interaction in the murine knee joint in vivo. Balb/c mice were injected with 50 microl of a 0.5-microm polystyrene particle suspension (0.1% v/v) into the knee joint. The severity of the inflammatory response was evaluated at days 1, 2, 3, 5, 7 (acute), 21 (intermediate), and 63 (chronic) after particle injection. Histological examination as well as assessment of the synovial microcirculation using intravital microscopy was performed. For the intravital microscopy measurements, the patella tendon was partially resected for visualization of the synovial tissue of the knee joint and the fluorescent markers FITC-dextran and rhodamine 6G were injected intravenously. There was a significantly enhanced leukocyte-endothelial cell interaction beginning at day 3 after particle injection with a maximum in the acute phase (days 5-7) and a subsequent decline in the intermediate (day 21) and chronic (day 63) phases. Functional capillary density was significantly increased from day 3 until day 21 after particle application. The histological examination showed an inflammatory reaction that complied widely with the temporal course of the microvascular parameters and resembled the histological appearance of the synovial-like membrane around loose joint prostheses. A novel model was established for the qualitative and quantitative investigation of the particle-induced inflammatory response in the joint environment. It was shown for the first time that there is a significantly enhanced leukocyte-endothelial cell interaction in the synovial tissue after intra-articular particle injection. This model seems to be suitable for further investigations, e.g., dealing with the biocompatibility of different particle materials.     

C-reactive protein levels after 4 types of arthroplasty

Background and purpose Postoperative C-reactive protein (CRP) levels in serum appear to reflect surgical trauma. We examined CRP levels after 4 types of arthroplasty.Material and methods We investigated 102 patients who had total knee arthroplasty (TKA), computer navigation-assisted total knee arthroplasty (NAV-TKA), hip resurfacing arthroplasty (metal on metal, MMSA) and total hip arthroplasty (THA), respectively. CRP levels were estimated before surgery and postoperatively at 2 and 7 days.Results Postoperatively, the peak CRP levels were highest on the second day after surgery in each of the groups. The peak CPR levels after hip resurfacing were lower than those after conventional primary THA. The peak CRP levels after computer navigation-assisted TKA were lower than those after conventional primary TKA.Interpretation The extent of bone and bone marrow injury rather than the region of surgery or the amount of soft tissue damage appears to determine the extent of the postoperative CRP response.     

Meniscus transplantation using a cryopreserved allograft--an experimental study in the rabbit

In twenty rabbits with completion of bone growth, the medial meniscus was replaced with an allograft meniscus that had been preserved at -80 degrees C for 6 to 14 days. As a control, the medial meniscus was removed and reattached without cryopreservation in 14 rabbits. Replaced menisci were examined histologically and microangiographically. Allografted menisci were found to attach to the capsule at 4 weeks. However, the attachments of the anterior and posterior horns were not stable in the majority of rabbits, because the nylon thread for anchoring was broken in these cases. There was osteophyte formation on the medial tibial plateau and the medial femoral condyle. Histological examinations revealed proliferation of vascularized synovial tissue along the meniscal surface and invasion of para-meniscal connective tissue into the meniscal substance. Chondrocytes showed regeneration in the superficial layer at 12 weeks. This study has demonstrated that cryopreserved meniscal allograft was capable of regeneration. The osteophyte formation of the medial femoral condyle and the tibial plateau appears to be produced by the abnormally unstable transplanted meniscus resulting from the insufficient anchorage of anterior and/or posterior horns.     

Editorial Commentary: Stem Cells. They Are in the Fat Tissue,Bone Marrow,and Even in the Synovial Fluid of the Knee Joint

Adult stem cells have been isolated in bone marrow and adipose tissue. These mesenchymal stromal cells (MSCs) have the ability to differentiate into osteogenic, chondrogenic, and adipogenic cell lines. The study by Branch et al. has identified MSCs in the synovial fluid of the knee in patients after anterior cruciate ligament injury and in patients with osteoarthritis of the knee. When mixing synovial fluid with whole blood and using a commercially available platelet-rich plasma–processing system, the total number of MSCs doubled in both groups when compared with the cell count in synovial fluid only. However, it is not clear whether the MSCs in the processed synovium–whole blood mix include synovial MSCs versus MSCs from only the blood. In addition, cell counts were substantially lower when compared with the typical concentrations of MSCs in bone marrow aspirate. The clinical application is yet to be defined.     

Synovial fluid biomarker levels predict articular cartilage damage following complete medial meniscectomy in the canine knee.

The purposes of this study were to document the histological changes present in the tibial plateaus 12 weeks after complete medial meniscectomy in dogs and to determine if synovial lavage fluid biomarker levels are predictive of the severity of joint damage. Twelve adult dogs underwent complete unilateral medial meniscectomy and synovial lavage fluid biomarker levels, including cartilage oligomeric matrix protein (COMP), keratan sulfate (5D4). 3B3(-), and 3B3(+), were measured serially at 4-week intervals. The dogs were euthanized 12 weeks after surgery and each medial and lateral tibial plateau from the meniscectomized and contralateral knees was graded histologically. Histological data were analyzed using principal components analysis, which resulted in 4 factors that explained 70% of the variation in the data. Factor 2 (weighted most heavily by subchondral bone thickness) and Factor 3 (representative of articular cartilage damage) were significantly affected by compartmental site (P < 0.01 for both). Both of these factors were highest in the medial tibial plateau of the meniscectomized knee, and Factor 3 was significantly higher in this site than in the medial tibial plateau of the contralateral knee (P < 0.01). Peak levels of all 4 synovial lavage fluid biomarkers occurred at 4 weeks post-meniscectomy and 4-week minus baseline levels of all biomarkers were significantly correlated with the Factor 3 scores. This study demonstrates that significant articular cartilage damage occurs relatively quickly following complete medial meniscectomy in dogs and establishes the content and criterion validity for these synovial fluid lavage biomarkers in canine meniscectomy as surrogate measures of articular cartilage damage.     

Effect of low-dose N-acetyl-cysteine infusion on tourniquet-induced ischaemia-reperfusion injury in arthroscopic knee surgery

BACKGROUND: Temporary occlusion of blood flow is used during arthroscopic knee surgery in order to provide a bloodless surgical field. The resulting ischaemia-reperfusion causes lipid peroxidation, which contributes to tissue injury. The aim of the study was to investigate the effect of low-dose n-acetyl cysteine (NAC) infusion on oxidative stress by determining malondialdehyde (MDA) levels during arthroscopic knee surgery. METHODS: Thirty patients, ASA I - II, undergoing arthroscopic knee debridement under a tourniquet were divided into NAC and control groups. Anaesthesia was induced with propofol, fentanyl and vecuronium bromide and maintained with desflurane in an equal parts O(2)-N(2)O mixture. In the NAC group, an infusion of NAC, 5 mg kg(-1).h(-1), was started after intubation, and continued until extubation. An equal volume of saline was infused to the control group. Duration of ischaemia, anaesthesia time, total dose of NAC infused were also recorded. Venous blood and synovial membrane tissue samples were obtained 10 min after the onset of NAC infusion but before tourniquet inflation (t1), after 30 min of ischaemia (t2), and after 5 min of reperfusion following tourniquet release (t3). RESULTS: Plasma MDA levels were significantly lower in the NAC group on reperfusion. There were no differences between the groups in tissue MDA levels at ischaemia and reperfusion times. CONCLUSION: Low-dose n-acetyl cysteine infusion attenuates lipid peroxidation and ischaemia-reperfusion injury in arthroscopic knee surgery requiring tourniquet application.     

Early recovery after fast-track Oxford unicompartmental knee arthroplasty. 35 patients with minimal invasive surgery

Background and purpose

After total knee arthroplasty with conventional surgical approach, more than half of the quadriceps extension strength is lost in the first postoperative month. Unicompartmental knee arthroplasty (UKA) operated with minimally invasive surgery (MIS) results in less operative trauma. We investigated changes in leg-extension power (LEP) in the first month after MIS Oxford UKA and its relation to pain, knee motion, functional performance, and knee function.

Patients and methods

In 35 consecutive Oxford UKA patients, LEP was measured 1 week before and 1 month after surgery together with knee motion, knee swelling, the 30-second chair-stand test, and Oxford knee score. Assessment of knee pain at rest and walking was done using a visual analog scale.

Results

30 patients were discharged on the day after surgery, and 5 on the second day after surgery. LEP and functional performance reached the preoperative level after 1 month. Only slight postoperative knee swelling was observed with rapid restoration of knee flexion and function. A high level of pain during the first postoperative night and day fell considerably thereafter. None of the patients needed physiotherapy supervision in the first month after discharge.

Interpretation

Fast-track MIS Oxford UKA with discharge on the day after surgery is safe and leads to early recovery of knee motion and strength even when no physiotherapy is used.After total knee arthroplasty (TKA), more than half of the preoperative quadriceps strength is lost in the first month after surgery (Mizner et al. 2005). TKA surgery with minimally invasive surgery (MIS) may lead to less postoperative pain, shorter length of stay in hospital, and greater knee flexion (Chen et al. 2006), and the MIS approach may result in better outcome with regard to maintaining extensor strength than the conventional surgical approach (Kim et al. 2010). In unicompartment knee arthrosis, the Oxford Group recommend unicompartmental knee arthroplasty (UKA) operated with MIS, since recovery is twice as fast as after the conventional approach and damage to the soft tissue of the joint is greatly diminished (Price et al. 2001). Althrough fast-track UKA with length of stay of about 1.5 days has been described (Reilly et al. 2005), there have been few reports on quadriceps strength after UKA (Mancher et al. 2002) and to our knowledge there have been no reports on early leg-extension power (LEP) after UKA.We studied changes in LEP within the first month after fast-track MIS Oxford Phase III medial UKA in relation to pain, knee motion, functional performance, knee function, and the need for physiotherapy after discharge.