Knee Joint Capsule Research Articles

Expression and significance of β-catenin and NF-κB signaling pathway in knee osteoarthritis synovial inflammation

To explore expression of β-catenin and NF-κB signaling pathway in synovial tissue of rats with different degrees of knee osteoarthritis (KOA). Forty-eight SPF male rats weighed (200±20) g were randomly divided into three groups, namely model group (32 rats), sham operation group (8 rats) and control group (8 rats). KOA model rats were established by Hulth method, and 8 rats were killed at 2, 4, 8, 12 weeks respectively after modeling, in order to establish KOA model rats with moderate, early, mild and severe degree. Sham operation group was only cut off capsule of knee joint and suture to exclude interference factor, control group was untreated. Behavior, synovial hyperplasia and cartilage degeneration of rats among each group were observed. Expression of NF-κB and signaling pathway and β-catenin in synovial tissue of rats were detected by real-time PCR. KOA rat model was successfully established, and synovial hyperplasia was observed in KOA model at mild and early degree, and then gradually decreased; while cartilage degeneration in the early moderate and severe KOA model was significantly expressed, and gradually aggravated with time. The results of PCR showed that expression of β-catenin in 4-week group (8.57±0.46) and 8-week group (4.23±0.09) were higher than those in control group (P<0.05); expression of TLR-2 in 2-week group (12.04±4.02) and 4-week group (8.54±2.13) were higher than those in control group(P<0.05), and TLR-4 in 2-week group(5.04±0.93), 4-week group (3.29±0.58) and 8-week group (1.63±0.12) were higher than those in control group; expression of NF-κB was significantly higher in 2-week group (10.15±2.04), 4-week group (15.97±4.17), 8-week group (7.69±1.48) and 12-week group (6.70±1.58) than that in control group (P<0.05), and expression of IL-1β was significantly higher in 4-week group (2.79±0.25) and 8-week group (2.46±0.32) than that of control group (P<0.05). On the RNA expression level, both of β-catenin and NF-κB signaling pathways are involved in synovial inflammation in KOA model rats, and they play a regulatory role in expression of IL-1β, degeneration of KOA.

Distribution of sensory nerves supplying the knee joint capsule and implications for genicular blockade and radiofrequency ablation: an anatomical study

Despite their emerging therapeutic relevance, there are many discrepancies in anatomical description and terminology of the articular nerves supplying the human knee capsule. This cadaveric study aimed to determine their origin, trajectory, relationship and landmarks for therapeutic purpose. We dissected 21 lower limbs from 21 cadavers, to investigate the anatomical distribution of all the articular nerves supplying the knee joint capsule. We identified constant genicular nerves according to their anatomical landmarks at their entering point to knee capsule and inserted Kirschner wires through the nerves in underlying bone at those target points. Measurements were taken, and both antero-posterior and lateral radiographs were obtained. The nerve to vastus medialis, saphenous nerve, anterior branch of obturator nerve and a branch from sciatic nerve provide substantial innervation to the medial knee capsule and retinaculum. The sciatic nerve and the nerve to the vastus lateralis supply sensory innervation to the supero-lateral aspect of the knee joint while the fibular nerve supplies its infero-lateral quadrant. Tibial nerve and posterior branch of obturator nerve supply posterior aspect of knee capsule. According to our findings, five constant genicular nerves with accurate landmarks could be targeted for therapeutic purpose. The pattern of distribution of sensitive nerves supplying the knee joint capsule allows accurate and safe targeting of five constant genicular nerves for therapeutic purpose. This study provides robust anatomical foundations for genicular nerve blockade and radiofrequency ablation.

Effects of losartan and atorvastatin on the development of early posttraumatic joint stiffness in a rat model.

BackgroundAfter a trauma, exuberant tissue healing with fibrosis of the joint capsule can lead to posttraumatic joint stiffness (PTJS). Losartan and atorvastatin have both shown their antifibrotic effects in different organ systems.ObjectiveThe purpose of this study was the evaluation of the influence of losartan and atorvastatin on the early development of joint contracture. In addition to joint angles, the change in myofibroblast numbers and the distribution of bone sialoprotein (BSP) were assessed.Study design and methodsIn this randomized and blinded experimental study with 24 rats, losartan and atorvastatin were compared to a placebo. After an initial joint injury, rat knees were immobilized with a Kirschner wire. Rats received either losartan, atorvastatin or a placebo orally daily. After 14 days, joint angle measurements and histological assessments were performed.ResultsLosartan increased the length of the inferior joint capsule. Joint angle and other capsule length measurements did not reveal significant differences between both drugs and the placebo. At cellular level both losartan and atorvastatin reduced the total number of myofibroblasts (losartan: 191±77, atorvastatin: 98±58, placebo: 319±113 per counting field, p<0.01) and the percentage area of myofibroblasts (losartan: 2.8±1.8% [p<0.05], atorvastatin: 2.5±1.7% [p<0.01], vs control [6.4±4%], respectively). BSP was detectable in equivalent amounts in the joint capsules of all groups with only a trend toward a reduction of the BSP-stained area by atorvastatin.ConclusionBoth atorvastatin and losartan reduced the number of myofibroblasts in the posterior knee joint capsule of rat knees 2 weeks after trauma and losartan increased the length of the inferior joint capsule. However, these changes at the cellular level did not translate an increase in range of motion of the rats´ knee joints during early contracture development.

Evaluation of the iPACK block injectate spread: a cadaveric study

Background and objectivesUltrasound-guided infiltration of the interspace between the popliteal artery and capsule of the knee (iPACK) block, a new regional analgesic technique, is believed to relieve posterior knee pain,...

Atraumatic Calf Swelling In Recreational Cyclist

HISTORY: 51 year-old male presented with intermittent left calf pain and swelling for the past 2 months. The pain and swelling became constant the week preceding his presentation. He had no known injury but first noticed the pain after a spin class 2 months ago. The pain was worse with cycling, jogging, and swimming and at the end of the day. He had no knee pain, ankle pain, or hip pain. He denied lower extremity weakness or numbness. The pain did not radiate. PHYSICAL EXAMINATION: There was a soft tissue enlargement in posterior medial aspect of left calf that was mildly tender to palpation, soft, and non-mobile. Transillumination of the area was positive. No overlying erythema or skin changes were noted. Calf musculature and strength were normal. There was no tenderness along the rest of the gastrocnemius or Achilles tendon and no pretibial edema was present. Neurovascular examination was unremarkable. DIFFERENTIAL DIAGNOSIS: 1. Deep Vein Thrombosis 2. Synovial Cyst 3. Abscess 4. Morel-Lavallée lesion 5. Lipoma 6. Hematoma TESTS AND RESULTS: - Knee x-rays: Grossly normal; generally preserved joint space, with osteophyte formation and mild patellofemoral arthritis - Bedside ultrasound of calf: Large, hypoechoic, cystic appearance; connected with a small stalk to the posterior knee joint capsule (popliteal); no vascularity seen on Color Flow Doppler - Fluid analysis: Yellow, hazy; no crystals seen; minimal nucleated cells FINAL/WORKING DIAGNOSIS: Synovial cyst connected to the popliteal aspect of the knee joint TREATMENT AND OUTCOMES: 1. Bedside ultrasound evaluation 2. Aspiration of popliteal cyst, 85cc of straw-colored fluid, sent for analysis 3. ACE wrap recommended in attempt to prevent re-accumulation of fluid 4. Orthopedic evaluation due to re-accumulation of fluid, recommended continued monitoring given asymptomatic nature 5. Could consider surgical excision if becomes symptomatic

Comparative morphofunctional and species-specific vascularization features of of the knee capsule of some mammals

The metabolic, reparative and plastic properties, as well as the functional activity of the multiorgan synovial environment of the knee joint, are organically and functionally related to their morphology and blood supply. The aim of our research was to determine the general biological and specific features of the structural organization and vascularization of the knee joint capsule in animals with different supports, locomotion and body weight. A complex of morphological research methods is used in this work: anatomical, histological, neurohistological. Used neurohistological method of impregnation in its own algorithm. The structural organization of synovial and fibrous capsule, histotopography of intraorganic vessels was studied on 43 objects of various groups of animals. The selection of animals was carried out according to the type of limb specialization to the substrate. Animals were taking into account the ecology, types of support, the nature of locomotion and the speed of movement – phalanoid animals – a domestic horse, a domestic bull and a finger animal – a domestic dog and a domestic cat. As a result of the complex comparative-morphological study the general patterns of the structural organization of the articular capsule, the general-biological and species-specific features of the angioarchitectonics and angiotopography were established. The zones of the most intense intraorganic vascularization and the topography of the vascular fields and glomeruli of the articular capsule are shown. The zones of intensive vascularization are localized: in the domestic bull – in the medial, dorsal, lateral parts, vascular glomeruli – in the lateral; in the domestic horse – in all parts of the capsule, vascular glomeruli – in the plantar area; in the domestic dog – in the medial, dorsal, plantar parts, vascular glomeruli – in the plantar area; in a domestic cat, the same type of angioarchitectonics is observed, the vascular fields and glomeruli are absent. The more intense angioarhitectonics in the capsule of the knee joint in phalanoid animals (horse, cattle) than in the finger (dog, cat) possibly due to the different nature of the support and type of locomotion, is determined. Key words: vascular fields, vascular glomeruli, angioarchitectonics, knee joint, joint capsule, domestic horse, domestic bull, domestic dog, domestic cat.

A Mini-Invasive Internal Fixation Technique for Studying Immobilization-Induced Knee Flexion Contracture in Rats.

Joint contracture, resulting from a prolonged joint immobilization, is a common complication in orthopedics. Currently, utilizing an internal fixation to restrict knee joint mobility is a widely accepted model to generate experimental contracture. However, implanting application will inevitably cause surgical trauma to the animals. Aiming to develop a less invasive approach, we combined a muscle-gap separation modus with a previously reported mini-incision skill during the surgical procedure: Two mini skin incisions were made on the lateral thigh and leg, followed by performing muscle-gap separation to expose the bone surface. The rat knee joint was gradually immobilized by a preconstructed internal fixation at approximately 135° knee flexion without interfering essential nerves or blood vessels. As expected, this simple technique permits rapid postoperative rehabilitation in animals. The correct position of the internal fixation was confirmed by an x-ray or micro-CT scanning analysis. The range of motion was significantly restricted in the immobilized knee joint than that observed in the contralateral knee joint demonstrating the effectiveness of this model. Besides, histological analysis revealed the development of fibrous deposition and adhesion in the posterior-superior knee joint capsule over time. Thus, this mini-invasive model may be suitable for mimicking the development of immobilized knee joint contracture.

Ultrasound elastographic assessment of the stiffness of the anteromedial knee joint capsule at varying knee angles.

In vivo evaluation of the elastic properties of the knee joint capsule has not been adequately performed. To establish a methodology to assess the stiffness of the normal knee joint capsule over a range of knee flexion angles using ultrasound elastography. Ultrasound elastography with an acoustic coupler was used to assess the stiffness of the anteromedial capsule of the knee joints of 10 male (mean age 22.63 ± 1.02 years) and 10 female (mean age 21.6 ± 0.8 years) subjects at static knee flexion angles of 0°, 45°, 90°, and 120°. Relative stiffness of the capsule was obtained using the strain ratio (SR), defined as the ratio of the strain in the capsule to that in the acoustic coupler. The intraclass correlation coefficient (1, 3) ranged from 0.95 to 0.96, and the correlation coefficient between examiners (2, 3) was 0.94. SR values decreased significantly as the flexion angle increased (P <0.01). At 90° and 120°, it was significantly higher in female than in male subjects (P <0.01). This study established a feasible and reproducible method to obtain the stiffness characteristics of the anteromedial knee joint capsule using ultrasound elastography with an acoustic coupler.

The anatomy of the anterolateral structures of the knee — A histologic and macroscopic approach

BackgroundThe anatomy of the anterolateral structures of the knee is complex and still controversial. The aim of our study was to analyze this anatomy by histologic and macroscopic evaluation, with a particular emphasis on the anterolateral ligament (ALL). Material and methodsTwenty-three cadaveric knee joints were dissected followed by a qualitative and quantitative anatomic analysis of the anterolateral knee structures. Histology and comparison of different anterolateral structures was performed in addition. ResultsThe ALL was identified in all of the dissected cadaveric knee specimens. It runs in an oblique course from its proximo-dorsal insertion at the distal femur into a ventro-distal direction to the anterolateral tibia. The femoral insertion site was found to be posterior and slightly proximal to the lateral femoral epicondyle and the femoral attachment of the lateral collateral ligament (LCL). The femoral insertion of the ALL overlapped the LCL in all dissected knees. The tibial insertion site was midway between Gerdy's tubercle (GT) and the tip of the fibular head (FH). In 15 of the dissected 23 knee joints, thin attachments to the lateral meniscus were observed. Histology confirmed differences in the composition of the anterolateral knee joint capsule, the ALL and the iliotibial band (ITB). ConclusionsThe ALL occurs as a regular separate anterolateral ligamentous structure. It is distinguishable from the ITB and the anterolateral joint capsule in both embalmed and non-embalmed specimens. Histology of the ALL indicates typical ligamentous tissue which clearly differs from the anterolateral knee joint capsule and the thicker ITB. Level of evidenceLevel II, descriptive anatomic study.

Analgesic strategies for day-case knee surgery.

Analgesic strategies for day-case knee surgery.

Anatomical study of the innervation of posterior knee joint capsule: implication for image-guided intervention

Background and objectivesPeripheral nerve block is an important component of the multimodal analgesia for total knee arthroplasty. Novel interventional techniques of ultrasound-guided nerve block supplying the posterior knee joint capsule...

Stiffness of knee joint capsule using strain ultrasound elastography

Stiffness of knee joint capsule using strain ultrasound elastography

The effects of barbed suture on watertightness after knee arthrotomy closure: a cadaveric study

BackgroundWound closure is one of the crucial aspects of total knee arthroplasty (TKA) for patients who perform high-flexion activities of daily living, because the joint capsule is highly stretched and integrity of the arthrotomy closure must be maintained. Watertightness of the knee joint is a different aspect of the repair integrity of arthrotomy closure and is being noticed with increasing usage of the drain clamp method for blood management after TKA. Recently, the barbed knotless suture has been growing in popularity as a strong, secure closure appropriate for high-tension areas, such as the fascia and joint capsule. The purpose of this study was to compare the barbed knotless suture with simple interrupted suture in cadaveric knees.MethodsNine fresh-frozen cadaveric lower extremities were used. After placing a parapatellar incision and setting a closed suction drain, arthrotomies were closed randomly using three suture materials: simple interrupted absorbable suture (No. 0 PDS, group C); or a single running knotless barbed suture Stratafix with 8N (group BS-8N) or 15N (group BS-15N) of tension. After arthrotomy closure, saline was injected in a retrograde manner into the joint through a drain until saline started to leak from the joint. Peak values for intra-articular pressure and infusion volume in each group were recorded and compared.ResultsMean infusion volumes were 13.0 ± 7.2 ml, 38.6 ± 10.7 ml, and 5.1 ± 2.5 ml in groups BS-8N, BS-15N, and C, respectively. Mean intra-articular pressures were 0.67 ± 0.47 kPa, 9.44 ± 4.55 kPa, and 0.56 ± 0.44 kPa in groups BS-8N, BS-15N, and C, respectively. Infusion volume and joint internal pressure were significantly higher in group BS-15N than in groups BS-8N (p = 0.008) or C (p = 0.04).ConclusionsBarbed suture with 15N appears appropriate for maintaining maximal watertightness after knee joint capsule closure, offering successful drain clamping, higher resistance to early mobilization protocols, and subsequent achievement of early deep knee flexion after TKA.

The effect of a fibrin sealant on knee function after total knee replacement surgery. Results from the FIRST trial. A multicenter randomized controlled trial.

BackgroundTotal knee replacement (TKR) is increasingly performed in short term hospital stay, making same day mobilization an important issue is after surgery. This implies little joint effusion by reducing intra-articular blood loss, which will enhance knee range of motion. The application of a topical fibrin sealant on the intraoperative bare bone and synovial tissue may contribute to better early full mobilization and thus improved functional outcomes. Since ambulation with a fully extended knee is less strenuous, we hypothesized that patients who received fibrin sealant would demonstrate improved early knee extension after six weeks compared to patients who received standard care.MethodsA multicenter randomized controlled trial in a consecutive series of osteoarthritis patients scheduled for TKR surgery. Participants were randomized to receive fibrin sealant or not before closing the knee joint capsule. Primary outcome was change in knee extension angle(°) at short term (2 weeks) follow-up (cExt). Secondary outcomes were 6-week extension angle, knee flexion angle, hemoglobin loss, blood transfusion rates, complication rates, the Knee Society Score, and the KOOS and EQ5D questionnaires.ResultsWhen data on primary outcome became available from 250 patients, an interim analysis was performed by an independent Data Safety Monitoring Board for safety and effectivity assessment. This analysis showed that sufficient patients were included to detect a cExt of 10° between both groups. Inclusion was stopped however, all in the meantime included patients were treated according to their randomization. A total of 466 were available for analysis. Both groups were comparable in terms of baseline characteristics. The estimated mean cExt difference was 0.2° (95%CI -0.5 to 0.9). No differences in secondary outcomes were found.ConclusionsNo beneficial effects or side effects were found of a topically applied fibrin sealant during TKR surgery. These results discourage the clinical use of a fibrin sealant in TKR.Trial registrationDutch Trial Register, NTR2500.

Strategy for wound repair of skin and soft tissue defect and systematic rehabilitation treatment for functional reconstruction of patients with severe burn or trauma on knees

Objective: Strategy for wound repair of skin and soft tissue defect and systematic rehabilitation treatment for functional reconstruction of patients with severe burn or trauma on knees. Methods: From January 2015 to October 2016, 26 patients with skin and soft tissue defect on knees after severe burn or trauma were hospitalized in our unit. Among these patients, 14 patients had patellar ligament defect, and 16 patients had knee joint capsule defect. Wound debridement was operated on 1 to 3 days after admission. After debridement, the area of skin and soft tissue defect ranged from 10 cm×7 cm to 42 cm×18 cm. Vacuum sealing drainage (VSD) treatment was performed after debridement, and flap transplantation operation was performed after VSD treatment for 5 to 7 days. Defects of nine patients were treated with local rotation flaps. Seven patients with skin and soft tissue defects on knees and knee joint capsule defects of 5 cm×3 cm to 9 cm×7 cm were treated with free anterolateral femoral flaps combined with fascia lata. Ten patients with skin and soft tissue defects on knees and patellar ligament defects of 6 cm×3 cm to 12 cm×4 cm were treated with free anterolateral femoral flaps combined with iliotibial tract. The area of flaps ranged from 11 cm×9 cm to 22 cm×15 cm. After flap transplantation operation, functional reconstruction of knee joint was carried out according to early, continuous, and sequential systematic rehabilitation treatment strategy. The pain degree and function of knee joint of patients were scored by the International Knee Documentation Committee (IKDC) Knee Evaluation Form before operation and 12 months after operation. The knee joint flexion and extension degrees of patients were measured by joint protractor in 2 weeks and 12 months after operation. The color Doppler ultrasound was used to evaluate integrity of knee joint capsule and continuity of patellar ligament of patients in 6 and 12 months after operation. Results: All flaps of 26 patients survived well, and wounds healed completely after the operation. Distal parts of flaps of 2 patients treated with free anterolateral femoral flaps had local necrosis after the operation, and their wounds healed after debridement and transplantation of autologous intermediate split-thickness skin graft of thigh. The IKDC Knee Evaluation Form score of patients was (79±8) points in 12 months after operation, which was significantly higher than (64±7) points before operation (t=7.20, P<0.05). The flexion degree of knee joint of patients was (117±10)° in 12 months after operation, which was significantly larger than (35±8)° in 2 weeks after operation (t=32.65, P<0.05). The extension degree of knee joint of patients was (12±9)° in 12 months after operation, which was significantly smaller than (61±9)° in 2 weeks after operation (t=19.63, P<0.05). In 6 and 12 months after operation, 9 patients treated with local rotation flaps had good integrity of knee joint capsule and continuity of patellar ligament; 7 patients treated with free anterolateral femoral flaps and fascia lata had good integrity of knee joint capsule; 10 patients treated with free anterolateral femoral flaps and iliotibial tract had good continuity of patellar ligament. During follow-up of 12 months, all flaps survived well; knees of all patients had good appearance; knee joints functioned normally. Conclusions: Good appearance and function of knees can be achieved by repairing wound of skin and soft tissue defect on knees after severe burn or trauma with local rotation flaps or free anterolateral femoral flaps with fascia lata or iliotibial tract plus systematic rehabilitation treatment of knee joint in early stage after flap transplantation operation.

Anatomical Study of the Innervation of Anterior Knee Joint Capsule: Implication for Image-Guided Intervention.

The knee joint is the most common site of osteoarthritis. While joint replacement is considered an ultimate solution, radiofrequency denervation may be contemplated in some cases. Radiofrequency ablation requires precise localization of the articular branches innervating the joint capsule. The objective of this cadaveric study was to determine the source, course, relationships, and frequency of articular branches innervating the anterior knee joint capsule. Fifteen knees were meticulously dissected. The number and origin of the articular branches were recorded, and their distribution defined by quadrants. Their relationships to anatomical landmarks were identified. The articular branches terminated in 1 of the 4 quadrants with minimal overlap. In all specimens, the superolateral quadrant was innervated by the nerve to vastus lateralis, nerve to vastus intermedius, superior lateral genicular and common fibular nerves; inferolateral by the inferior lateral genicular and recurrent fibular nerves; superomedial by the nerve to vastus medialis, nerve to vastus intermedius and superior medial genicular nerve; and inferomedial by the inferior medial genicular nerve. In 3 specimens, the inferomedial quadrant also received innervation from the infrapatellar branch of saphenous nerve. All articular branches except the nerves to vastus lateralis and medialis course at the periosteal level. The frequency map of the articular branches provides an anatomical basis for the development of new clinical protocols for knee radiofrequency denervation and perioperative pain management.

Cadaveric study of the infrapatellar branch of the saphenous nerve: Can damage be prevented in total knee arthroplasty?

BackgroundThe infrapatellar branch of the saphenous nerve (IPBSN) is a purely sensory nerve innervating the anteromedial aspect of the knee and anteroinferior knee joint capsule. Total knee arthroplasty (TKA) is commonly used to treat end-stage arthritis, but the IPBSN is often injured and results in numbness around the anteromedial knee. The aim of this cadaveric study was to describe the course and variability of the IPBSN and to assess whether it is possible to preserve during a standard midline surgical approach in TKA. MethodsTen fresh-frozen cadaver legs were dissected using a midline approach to the knee. Skin and subcutaneous flap were reflected to expose both the saphenous nerve and its branches. The branches of the IPBSN were identified, and their vertical distances above the tibial tuberosity (TB) were recorded: TB to inferior branch, to middle branch, and to superior branch. ResultsThere were 10 left-sided specimens (6 female, 4 male) with a mean age of 79.9 ± 9.8 years. 8 (80%) specimens had 2 branches of IPBSN while 2 (20%) specimens had 3 branches. The average distance from TB to the inferior branch was 16.8 ± 8.3 mm (3.0–28.0); middle branch, 24.0 ± 1.4 mm (23.0–24.9); and superior, 45.9 ± 7.7 mm (32.0–54.5). ConclusionOur cadaveric study found no consistent way to preserve the IPBSN using a standard midline approach in TKA. It is important to provide proper patient education on this complication, and surgeons should be aware of approximate locations and variations of IPBSN while performing other knee procedures.

Measurement of Stiffness of Knee Joint Capsule Using Ultrasound Elastography

Measurement of Stiffness of Knee Joint Capsule Using Ultrasound Elastography

Molecular pathology of total knee arthroplasty instability defined by RNA-seq

Total knee arthroplasty (TKA) is a durable and reliable procedure to alleviate pain and improve joint function. However, failures related to flexion instability sometimes occur. The goal of this study was to define biological differences between tissues from patients with and without flexion instability of the knee after TKA. Human knee joint capsule tissues were collected at the time of primary or revision TKAs and analyzed by RT-qPCR and RNA-seq, revealing novel patterns of differential gene expression between the two groups. Interestingly, genes related to collagen production and extracellular matrix (ECM) degradation were higher in samples from patients with flexion instability. Partitioned clustering analyses further emphasized differential gene expression patterns between sample types that may help guide clinical interpretations of this complication. Future efforts to disentangle the effects of physical and biological (e.g., transcriptomic modifications) risk factors will aid in further characterizing and avoiding flexion instability after TKA.

An anatomic study on the attachment of the joint capsule to the tibia in the lateral side of the knee.

The purpose of the current study was to examine the width, area, and histological characteristics of the capsular attachment to the tibia in the lateral side of the knee. A total of 27 knees were used in this study. The joint capsule of the knee was peeled away from the tibia and the width of the capsular attachment to the tibia was measured by two independent observers using a caliper. Interclass correlation coefficients for each value were calculated to evaluate the validity of the measurement. The capsular attachment to the tibia of the seven knees was histologically analyzed using Masson's trichrome staining. At the posterior border of Gerdy's tubercle, the capsular attachment was wide; the average width was 8.6mm (SD 3.0). Toward the posterolateral aspect of the knee, the capsular attachment gradually tapered. Finally, the capsular attachment was linear at the apex of the head of the fibula. Histological analysis at the posterior border of Gerdy's tubercle revealed developed uncalcified fibrocartilage on the capsular attachment. In contrast, at the apex of the head of the fibula, the joint capsule was adhered to the capsule of the proximal tibiofibular joint. Fibrous connective tissue was directly attached to the calcified fibrocartilage. The attachment width of the knee joint capsule at the lateral side varied according to location. We consider that this finding on the capsular attachment will facilitate an understanding of the pathology or mechanism of diseases on the lateral side of the knee joint.