Articular Cartilage Wear

Young patients with early osteoarthritis (OA) represent a challenging population due to a combination of high functional demands and limited treatment options. Conservative measures such as injection and physical therapy can provide short-term pain relief but are only palliative in nature. Joint replacement, a successful procedure in the older population, is controversial in younger patients, who are less satisfied and experience higher failure rates. Therefore, while traditionally not indicated for the treatment of OA, cartilage repair has become a focus of increased interest due to its potential to provide pain relief and alter the progression of degenerative disease, with the hope of delaying or obviating the need for joint replacement. The field of cartilage repair is seeing the rapid development of new technologies that promise greater ease of application, less demanding rehabilitation and better outcomes. Concurrent procedures such as meniscal transplantation and osteotomy, however, remain of crucial importance to provide a normalized biomechanical environment for these new technologies. Level of evidence Systematic review, Level II.

Physiochemical properties of biomaterials play critical roles in dictating types of cell behaviour. In this study, a series of poly(ε-caprolactone) (PCL)-derived polymers bearing different small chemical groups was employed as a platform to evaluate chondrogenesis of different cell types. Thin films were prepared by spin-coating PCL derivatives. Rabbit articular chondrocytes (rACs) and rabbit bone marrow-derived mesenchymal stem cells (rMSCs) were seeded on to the films, and cell adhesion, proliferation, extracellular matrix production and gene expression were evaluated. The presence of hydrophilic groups (-NH2 , -COOH, -OH and -C=O) promoted adhesion and proliferation of primary rACs and rMSCs. On these polymeric films, chondrogenesis of primary rACs depended on culture time. For passaged cells, re-differentiation was induced on these films by chondrogenic induction, but less for cells of passage 5 compared to passage 3. While films with hydrophilic groups favoured chondrocytic gen...

Background: Understanding the acute response of healthy knee cartilage to running may provide valuable insight into functional properties. In recent years, quantitative magnetic resonance (MR) imaging techniques (T1 r and T2 relaxation measurement) have shown tremendous potential and unique ability to noninvasively and quantitatively determine cartilage response to physiologic levels of loading occurring with physiologic levels of exercise.

Physiological studies have shown that focal articular surface defects in the human knee may progress to degenerative arthritis. Although the risk of this evolutive process is multifactorial, defect size is one of the most important factors. In order to determine the influence of osteochondral defect size and location on the stress and strain concentrations around the defect rim, a finite element model of the human knee was developed. From our results, it became clear that the size and location of cartilage defects drastically affect to those variables. No stress concentration appeared around the rim of small defects, being the stress distribution mainly controlled by the meniscus contact. On the contrary, important rim stress concentration was found for large osteochondral defects. This alteration of the stress distribution has important clinical implications regarding the long-term integrity of the cartilage adjacent to osteochondral defects. ᭧ (E. Peña), [email protected] (B. Calvo), [email protected] (M. Martínez), [email protected] (M. Doblaré). 0010-4825/$ -see front matter ᭧

Objective. Since fibroblasts in the synovium of patients with rheumatoid arthritis (RA) express the serine proteases fibroblast activation protein (FAP) and dipeptidylpeptidase 4 (DPP-4)/CD26, we undertook the current study to determine the functional role of both enzymes in the invasion of RA synovial fibroblasts (RASFs) into articular cartilage.

Activation of nuclear factor kappa B (NF-jB) in synovial cells is seen in RA and OA patients. Caffeic acid phenethyl ester (CAPE) is a specific and potent inhibitor of NF-jB. We aimed to determine the in vivo effects of intra-articular injections of CAPE on cartilage in an ...

Objective: The damage to cartilage collagen is a central event in the pathogenesis of cartilage aging and osteoarthritis (OA). We have previously developed an in vitro model of cartilage degradation which shows that chondrocyte-dependent lipid peroxidation mediates cartilage collagen degradation. The goal of our study was to investigate the role of vitamin C in this degradation model and to investigate effect of chondrocyte-dependent lipid peroxidation in the oxidation of cartilage collagen. Methods: We studied primary articular chondrocytes. Effect of vitamin C was investigated in the previously described model. Serum-free stimulated and unstimulated chondrocyte-matrix extracts were subjected to SDS-PAGE and immunoblot analysis. Malondialdehyde (MDA)-protein oxidation of cartilage proteins was demonstrated by the reactivity of chondrocyte extracts to a monoclonal antibody, MDA2, which detects MDA-lysine adducts. Results: Vitamin C treatment of chondrocyte cultures resulted in significant enhanced incorporation of 3H-proline label in cell-matrix. Cells treated with vitamin C, as compared to control untreated cells showed decreased spontaneous release of labeled matrix. Vitamin C treated or not treated chondrocytes responded comparably to stimulation with the agonist calcium ionophore A23187. The serum-free in vitro culture of chondrocytes resulted in MDA-protein oxidation. The treatment of chondrocytes with A23187 resulted in the enhancement of MDA-protein oxidation. The immunoblot reactivity pattern of extracts to MDA2 antibody and to polyclonal anti-type II collagen antibody was somewhat similar, which suggests that these two different types of antisera exibit a crossreaction to chondrocyte proteins. Chondrocyte extracts were pretreated both with and without pure collagenase, and then subjected to immunoblot analysis. Only collagenase treated extracts showed a disappearence, or significant reduction, of larger than 60 kDa size MDA2 immunoreactive proteins. This suggests that the proteins that disappeared after the enzyme treatment were collagen proteins and which had also been modified by MDA oxidation. Conclusions: These observations suggest that collagen hydroxylation of matrix by vitamin C does not play a role in this model of chondrocyte-dependent collagen degradation. Also, this study demonstrates that chondrocyte-derived lipid peroxidation product MDA mediates oxidation of cartilage collagens. Oxidative modification of cartilage collagen in vivo could result in alteration of biochemical and biophysical properties of cartilage collagen fibrils, making them prone to degradation, thus initiating the changes observed in aging and OA.

The aim of this retrospective study was to evaluate the clinical and radiographic outcomes of arthroscopic partial meniscectomy for complete posterior medial meniscus root tear (PMMRT) in patients with early radiographic evidence of knee osteoarthritis at a minimum follow-up of 5 years. Methods: Forty-six cases had complete PMMRT with follow-up of at least 5 years and were treated with arthroscopic partial meniscectomy. On the basis of medical records, we reviewed the arthroscopic findings of joint degeneration (Outerbridge grading), clinical results using the modified Lysholm (ML) knee score and a patient questionnaire, and radiographic evaluation of degeneration using Kellgren-Lawrence (KL) grading. Results: The incidence of complete PMMRT in the study population was 15%. At a mean follow-up of 78 months (range, 60 to 103 months), the mean ML score significantly improved from 72 (range, 62 to 78) preoperatively to 77 (range, 70 to 98) at final follow-up (P Ͻ .01), 16 patients (35%) showed progression of degeneration from KL grade 0 to 2 preoperatively to KL grade 2 to 4, 56% of patients indicated improvement in pain, 67% of patients were satisfied with the results of the procedure, and 19% of patients underwent reoperation. There was a significant negative correlation between chondral wear during arthroscopy ( ϭ Ϫ0.516, P ϭ .002) and preoperative KL grade ( ϭ Ϫ0.429, P ϭ .004) with ML score at final follow-up. Conclusions: Although arthroscopic partial meniscectomy for complete PMMRT significantly improved ML scores postoperatively, only 56% of patients had improvement in pain, 67% were satisfied with the outcome of the procedure, and 35% showed radiographic progression of osteoarthritis at a mean follow-up of 77 months. Level of Evidence: Level IV, therapeutic study.

Objective: The microscopic study of the various components of joints provide a proper basis for understanding the nature of pathologic lesions to which they are subject and their imaging appearances. This study was designed to correlate MR imaging with a systematic histological study of the normal sacroiliac joint (SIJ), which to our knowledge is not available in the literature. Design and patients: Five male cadavers, aged 20 to 45 years, and seven male and seven female volunteers, aged 23 to 44 years, were investigated with oblique transaxial and coronal MR imaging of the SIJs. A variety of sequences including pre-and post-contrast T1 fat-saturated studies in the volunteers were used. Cryosectioning was performed in six SIJs of the five cadavers and compared with the MR images for the microscopic joint anatomy and assessed for the presence of abnormalities resembling those associated with sacroiliitis. Results: Throughout the SIJ, the hyaline cartilage of the sacral bone and the proximal third of the hyaline iliac cartilage was strongly attached to the surrounding stabilizing ligaments, forming wide margins of fibrocartilage. In the distal one-third of the joint only, the margins of the iliac joint facet resemble that of a synovial joint, which include an inner capsule with synovial cells. The MR anatomy of the ventral and dorsal nal MR imaging does not allow assessment of normal anatomy, variants or abnormalities of the ventral and dorsal margins of the cartilaginous SIJ.

Introduction: Low level laser therapy (LLLT) has been shown to enhance collagen production and wound healing but its effect on cartilage repair from biomechanical point of view is not known yet. The aim of present study was to evaluate the biomechanical behaviour of repairing osteochondral defect in rabbits which received a pulsed low-level gallium-arsenide (Ga-As) laser irradiation. Materials and methods: Osteochondral defects with 5 mm diameter and 4 mm in depth induced by drilling in right femoral patellar grooves of 41 adolescent male rabbits. They were divided into experimental and control groups. Experimental group received pulsed Ga-As (890 nm) laser irradiation with energy density of 4.8 J/cm 2 . The rabbits in control group received placebo LLLT with shut-down equipment. The control defects were allowed to heal spontaneously. Each group were divided into three subgroups: A, B and C. Subgroups A, B and C were sacrificed on 4, 8, and 16 weeks after surgery. The knee joint were removed, and the defects were examined biomechanically by in situ-indentation method. The thickness, instantaneous and equilibrium indentation stiffness was measured during the test. Data were analysed using ANOVA and independent sample t-test. Result: While no difference was observed in the repaired cartilage biomechanical properties among 4th, 8th, 16th weeks in study groups. The equilibrium indentation stiffness of experimental group was significantly higher in 8th week in comparison with control group. Conclusion: LLLT significantly enhances the stiffness of repairing tissue in the 8th week post injury in osteochondral defects in rabbits.

The effects of laser energy on articular cartilage were studied utilizing the neodymium YAG laser. Partial-thickness cartilage defects were surgically attempted in the femoral condyles of knee joints in guinea pigs. The defects were exposed to laser energy of varying intensities [group I, 25 J (5 W X 5 sec); group 11, 75 J (15 W x 5 sec); group 111, 125 J (25 W x 5 sec)]. A fourth group was studied, in which the defect was not lased. Animals were killed at weekly intervals from 1 to 6 weeks and the knee joints were subjected to histological analysis. At 5 weeks, the knees exposed to 25 and 75 J demonstrated a reparative process with chondral proliferation. The knees exposed to 125 J demonstrated fibrotic tissue and tissue necrosis that resulted in fibrosis. In the knees not exposed to laser energy, numerous foci of granulation tissue were present at all stages with the end point of healing being one of fibrosis with disorganized patchy cartilage islands.

Wrist arthroscopy is a valuable diagnostic and therapeutic tool. Thermal ablation can be used concomitantly to treat partial ligamentous tears, triangular fibrocartilage cartilage complex tears, and to perform partial synovectomy. We reviewed 47 consecutive patients who underwent wrist arthroscopy with concomitant thermal ablation between 1997 and 2001. Three patients sustained serious complications. The serious complications included, in all three patients, tendon ruptures and in one case, a 5 ϫ 10-mm full-thickness skin burn. Thermal treatment of collagenous tissues has recently gained popularity in the orthopedic literature, but there is little information on the potential complications. The arthroscopist of large and small joints must be aware of the risks involved when using thermal ablation.

Introduction: The purpose of the study was to prospectively assess patients with osteoarthritis of the knee selected for arthroscopic management (arthroscopic lavage and debridement, abrasion arthroplasty, microfracture, and radiofrequency (RF)-based chondroplasty). Methods: From 2003 to 2005, 108 patients with symptomatic primary osteoarthritis of the knee underwent arthroscopic management after medical treatment failure, of whom 92 were followed for a mean of 25 months (16 lost to follow-up). Pain was assessed using the pain domain, Knee Society Scoring System (Insall modification). Preoperative radiographic assessment was by Kellgren-Lawrence method; intraoperative severity of cartilage lesions were assessed using a modified Noyes grading system. Results: Mean age of 92 enrolled patients (98 knees) was 63 years (range, 22-84) and 56 (60%) were female. The medial compartment was more frequently and severely involved than the lateral compartment and PF joint, and Kellgren-Lawrence ...

Objective. To determine the role of articular cartilage lipids in its load-bearing function. Design. Normal and delipidised, bovine articular cartilage specimens were statically loaded and both the hydrostatic excess pore pressure and creep strain were measured. From this the compression stiffness of the skeletal structures of both types of matrices was determined.

Objectives: To investigate the frequency of chondrocyte apoptosis in equine articular cartilage (AC) specimens and to examine the relationship between the process of cell death and the degree of cartilage degradation using a direct quantification of numbers of apoptotic cells and expression of active caspase-3.

Background: Pentosan polysulfate sodium (pentosan) is a semi-synthetic drug manufactured from beech-wood hemicellulose by sulfate esterification of the xylopyranose hydroxyl groups. From in vitro and animal model studies, pentosan has been proposed as a disease modifying osteoarthritis drug (DMOAD). The objective of this study was to assess the efficacy, safety, and patient satisfaction in patients with mild radiographic knee osteoarthritis (OA) findings and OA-associated symptoms and signs. Methods: Twenty patients were assessed clinically at Nagasaki University Hospital. The radiographic indications of OA were grade 1 to 3 using the Kellgren-Lawrence Grading System (K/L grade). Pentosan used in this study was manufactured and supplied in sterile injectable vials (100 mg/ml) by bene GmbH, Munich, Germany. The study was a single-center, open-label trial. Treatment consisted of 6 weekly subcutaneous injections (sc) of pentosan (2 mg/kg). Patients were clinically assessed at entry and 1 to 8, 11, 15, 24 & 52 weeks post treatment. The results were analyzed using one way ANOVA and Dunnett's method. Results: Hydrarthroses were reduced quickly in all cases. The clinical assessments, i.e., knee flexion, pain while walking, pain after climbing up and down stairs, etc, were improved significantly and these clinical improvements continued for almost one year. The dose used in this study affected the blood coagulation test, but was within safe levels. Slightly abnormal findings were noted in serum triglycerides.

Osteoarthritis (OA) is a universal joint disease with significant socioeconomic effects. No cure for OA is available, but its early diagnosis could enable more efficient treatment. Currently, conventional, noninvasive ultrasound (<10 MHz) examination does not provide access to all joint surfaces and is limited to morphological information, with inadequate spatial accuracy to reveal cartilage microstructure. However, high-frequency (>10 MHz) ultrasound with a minimally invasive intra-articular approach enables not only enhanced resolution for imaging the diseased joint, but also assessment of biochemical and structural changes that affect the acoustic wave-tissue interactions. Therefore, several ultrasound parameters may be beneficial in examining tissue pathology. Ultrasound refection and backscatter from the superficial cartilage are sensitive to alterations in the collagen content and architecture. This enables high-resolution imaging and quantification of the surface fibrillation. Further, ultrasound attenuation (ranging from 1-147 dB/mm in the frequency range 5-100 MHz in normal tissue), speed (typically 1630 m/s in normal tissue), and backscatter from the internal cartilage depend on the tissue structure and composition and thus vary along with tissue degeneration. Ultrasound-assisted techniques such as mechano-acoustic indentation, elastography, and swelling measurements could enable the quantification of impaired mechanical properties of articular cartilage in disease. Although a number of challenges have to be met before the clinical use of ultrasound techniques in cartilage diagnostics is realistic, ultrasound and ultrasound-assisted techniques may enable assessment of the very early tissue changes in OA, so further studies are highly recommended.

Methods. Differential-display reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of a pool of messenger RNA (mRNA) from 10 human OA cartilage samples and 5 normal cartilage samples was performed using arbitrary primers. Confirmatory analysis of the up-regulated transcripts of fibronectin (FN) and osteopontin (OPN) was performed by RT-PCR of individual RNA samples from a separate set of donors. The effect of recombinant OPN (or anti-OPN antiserum) on chondrocyte function was examined by analyzing the spontaneous or interleukin-1 (IL-1)-induced release of nitric oxide (NO) and prostaglandin E 2 (PGE 2 ) from human OA-affected cartilage under ex vivo conditions.

The biomechanical properties of the zone of calcified cartilage (ZCC) in articulating joints are of clinical relevance due to the role ZCC plays in load transfer from cartilage to bone. To determine the micron-level mechanical properties and their correlation to mineral concentration in the ZCC, we combined nanoindentation (for micrometer level stiffness E r and hardness H) and quantitative back-scattered electron imaging or qBEI (for micrometer level mean calcium concentration Ca Mean ) to study the ZCC-subchondral bone junction in 3 embedded human patellae. Nanoindentation line scans were correlated to qBEI analysis in the ZCC. The correlation between local stiffness and local mineral content was different in calcified cartilage compared to bone. The stiffness and hardness of calcified cartilage was typically lower than subchondral bone for the same mineral content. ZCC showed a wider range of variation in calcium content (1-28 wt %) compared to subchondral bone (16-26 wt %). 2D material property maps of the ZCC were generated from the mechanical-mineral correlation, showing that bands of high and low stiffness were found between the bone and tidemark, and between the ZCC and the unmineralized cartilage.

This paper analyses the relationship between the thickness of the anterior femoral head cartilage (FHC), as measured by ultrasound, and some anthropometric parameters, such as height, weight, skeletal and chronological age. In addition, it provides standard norms for FHC thickness in a paediatric population. Both hips were examined in 213 consecutive subjects (99 boys and 114 girls), aged 1.9-14 years. Seventy-four subjects underwent hand and wrist X-rays for skeletal maturation: 32 of these were dropped from the study because a discrepancy as high as two standard deviations was found between their skeletal and their chronological age. The thickness of FHC correlated strongly with skeletal and chronological age, standing height and body weight. A side difference of 0.2 mm in FHC was considered to be abnormal. The study population was divided into 13 groups according to chronological age and values of FHC for boys and girls are provided for each group. It is suggested that the magnitude of hyaline FHC is a valuable feature in the evaluation of skeletal maturation in children.

Authors stated no financial relationship to disclose. Author contributions: Guarantor of integrity of entire study, T.J.M.; study concepts and design, T.J.M., H.E.S., C.C.; literature research, T.J.M.; experimental studies, T.J.M., H.E.S., C.C., J.H.; data acquisition, H.E.S., C.C., Y.L., J.H.; data analysis/interpretation, T.J.M., H.E.S., C.C., B.J.D.; statistical analysis, T.J.M., H.E.S., B.J.D., Y.L.; manuscript preparation, T.J.M., H.E.S., C.C., J.H.; manuscript definition of intellectual content, T.J.M.; manuscript editing and revision/review, T.J.M., H.E.S., C.C., B.J.D., M.B.S.; manuscript final version approval, all authors

Articular cartilage plays an important role in the function of diarthrodial joints. Computational methods have been used to study the biphasic mechanics of cartilage, and Abaqus has been one of the most widely used commercial software packages for this purpose. A newly developed open-source finite element solver, FEBio, has been developed specifically for biomechanical applications. The aim of this study was to undertake a direct comparison between FEBio and Abaqus for some practical contact problems involving cartilage. Three model types, representing a porous flat-ended indentation test, a spherical-ended indentation test, and a conceptual natural joint contact model, were compared. In addition, a parameter sensitivity study was also performed for the spherical-ended indentation test to investigate the effects of changes in the input material properties on the model outputs, using both FEBio and Abaqus. Excellent agreement was found between FEBio and Abaqus for all of the model types and across the range of material properties that were investigated.

With continued development and improvement of tissue engineering therapies for small articular lesions, increased attention is being focused on the challenge of engineering partial or whole synovial joints. Joint-scale constructs could have applications in the treatment of large areas of articular damage or in biological arthroplasty of severely degenerate joints. This review considers the roles of shape, loading and motion in synovial joint mechanobiology and their incorporation into the design, fabrication, and testing of engineered partial or whole joints. Incidence of degeneration, degree of impairment, and efficacy of current treatments are critical factors in choosing a target for joint bioengineering. The form and function of native joints may guide the design of engineered jointscale constructs with respect to size, shape, and maturity. Fabrication challenges for joint-scale engineering include controlling chemo-mechano-biological microenvironments to promote the development and growth of multiple tissues with integrated interfaces or lubricated surfaces into anatomical shapes, and joint-scale bioreactors which nurture and stimulate the tissue with loading and motion. Finally, evaluation of load-bearing and tribological properties can range from tissue to joint scale and can focus on biological structure at present or after adaptation.

The lateral ligaments of talocrural articulation, namely anterior talofibular liga- ment, posterior talofibular ligament and cal- caneofibular ligament, are important in an- atomic reconstruction. If reconstructed improperly, they are known to limit the movements of talocrural articulation and sub- talar articulation (talocalcaneal articulation) Studies on anatomy of anterior talofibular lig- ament, posterior talofibular ligament and cal- caneofibular ligament known as the lateral ligaments have some discrepancies. Knowing

BACKGROUND: Assessment of skeletal maturity in patients with adolescent idiopathic scoliosis (AIS) is important to guide clinical management. Understanding growth peak and cessation is crucial to determine clinical observational intervals, timing to initiate or end bracing therapy, and when to instrument and fuse. The commonly used clinical or radiologic methods to assess skeletal maturity are still deficient in predicting the growth peak and cessation among adolescents, and bone age is too complicated to apply. PURPOSE: To address these concerns, we describe a new distal radius and ulna (DRU) classification scheme to assess skeletal maturity. STUDY DESIGN: A prospective study. PATIENT SAMPLE: One hundred fifty young, female AIS patients with hand x-rays and no previous history of spine surgery from a single institute were assessed. OUTCOME MEASURES: Radius and ulna plain radiographs, and various anthropomorphic parameters were assessed. METHODS: We identified various stages of radius and ulna epiphysis maturity, which were graded as R1-R11 for the radius and U1-U9 for the ulna. The bone age, development of sexual characteristics, standing height, sitting height, arm span, radius length, and tibia length were studied prospectively at each stage of these epiphysis changes. RESULTS: Standing height, sitting height, and arm span growth were at their peak during stages R7 (mean, 11.4 years old) and U5 (mean, 11.0 years old). The long bone growths also demonstrated a common peak at R7 and U5. Cessation of height and arm span growth was noted after stages R10 (mean, 15.6 years old) and U9 (mean, 17.3 years old). CONCLUSIONS: The new DRU classification is a practical and easy-to-use scheme that can provide skeletal maturation status. This classification scheme provides close relationship with adolescent growth spurt and cessation of growth. This classification may have a tremendous utility in FDA device/drug status: Not applicable.

Osteoarthritis is one of the most frequent and chronic conditions that affect the U.S. population. Use of intra-articular injections is one of the established treatment options available in the nonoperative care for the management of symptomatic osteoarthritis. Common injectable medications include corticosteroids, hyaluronic acid, and other less traditional compounds (for example, botulinum toxin). Corticosteroids work by anti-inflammatory and antinociceptive actions. Corticosteroids have been shown to decrease pain and symptoms associated with osteoarthritis for up to 3 weeks. Hyaluronic acid has an unclear mechanism of action, but it is thought to promote the restoration of hyaluronic acid within an osteoarthritic joint. The efficacy of hyaluronic acid is modest and is most beneficial between 5 and 13 weeks after treatment. Other injectable compounds have been studied and include botulinum toxin type A, which has been theorized to work as an antinociceptive agent. One must be aware of the potential adverse effects associated with these medications. For all of these injectable treatments, the placebo effect must not be overlooked, because it has be demonstrated in multiple studies that these medications provide similar relief of pain when compared with placebo. Image guidance with ultrasound or fluoroscopy may be considered when performing intra-articular injections to improve accurate placement of medication.

Friction measurements of articular cartilage are important to determine the relative tribologic contributions made by synovial fluid or cartilage, and to assess the efficacy of therapies for preventing the development of post-traumatic osteoarthritis. Stanton's equation is the most frequently used formula for estimating the whole joint friction coefficient (m) of an articular pendulum, and assumes pendulum energy loss through a mass-independent mechanism. This study examines if articular pendulum energy loss is indeed mass independent, and compares Stanton's model to an alternative model, which incorporates viscous damping, for calculating m. Ten loads (25-100% body weight) were applied in a random order to an articular pendulum using the knees of adult male Hartley guinea pigs (n ¼4) as the fulcrum. Motion of the decaying pendulum was recorded and m was estimated using two models: Stanton's equation, and an exponential decay function incorporating a viscous damping coefficient. m estimates decreased as mass increased for both models. Exponential decay model fit error values were 82% less than the Stanton model. These results indicate that m decreases with increasing mass, and that an exponential decay model provides a better fit for articular pendulum data at all mass values. In conclusion, inter-study comparisons of articular pendulum m values should not be made without recognizing the loads used, as m values are mass dependent.

Wolff's ''law'' of the functional adaptation of bone is rooted in the trajectory hypothesis of cancellous bone architecture. Wolff often used the human proximal femur as an example of a trajectorial structure (i.e. arched trabecular patterns appear to be aligned along tension/compression stress trajectories). We examined two tenets of the trajectory hypothesis; namely, that the trabecular tracts from the tension-and compression-loaded sides of a bending environment will: (1) follow 'lines' (trajectories) of tension/compression stress that resemble an arch with its apex on a neutral axis, and (2) form orthogonal (901) intersections. These predictions were analysed in proximal femora of chimpanzees and modern humans, and in calcanei of sheep and deer. Compared to complex loading of the human femoral neck, the chimpanzee femoral neck reputedly receives relatively simpler loading (i.e. temporally/spatially more consistent bending), and the artiodactyl calcaneus is even more simply loaded in bending. In order to directly consider Wolff's observations, measurements were also made on two-dimensional, cantilevered beams and curved beams, each with intersecting compression/tension stress trajectories. Results in the calcanei showed: (1) the same nonlinear equation best described the dorsal (''compression'') and plantar (''tension'') trabecular tracts, (2) these tracts could be exactly superimposed on the corresponding compression/tension stress trajectories of the cantilevered beams, and (3) trabecular tracts typically formed orthogonal intersections. In contrast, trabecular tracts in human and chimpanzee femoral necks were non-orthogonal (mean $701), with shapes differing from trabecular tracts in calcanei and stress trajectories in the beams. Although often being described by the same equations, the trajectories in the curved beams had lower r 2 values than calcaneal tracts. These results suggest that the trabecular patterns in the calcanei and stress trajectories in short beams are consistent with basic tenets of the trajectory hypothesis while those in human and chimpanzee femoral necks are not. Compared to calcanei, the more complexly loaded human and chimpanzee femoral necks probably receive more prevalent/predominant shear, which is best accommodated by non-orthogonal, asymmetric trabecular tracts. The asymmetrical trabecular patterns in the proximal femora may also reflect the different developmental 'fields' (trochanteric vs. neck/head) that formed these regions, of which there is no parallel in the calcanei. Published by Elsevier Ltd.

Chondrale bzw. osteochondrale Läsionen von Gelenken sind typische Schädigungsmuster in der Orthopädie und Traumatologie. Aufgrund der in der Regel fehlenden Regeneration des verletzten Gelenkknorpels kann die initiale Läsion zur vorzeitigen Arthrose führen. Daher besteht ein großes Interesse an einer adäquaten Therapie dieser Schäden. Klinisch gebräuchliche Methoden der Knorpeltherapie sind derzeit Verfahren zur mesenchymalen Stammzellrekrutierung (autologe Knorpel-Knochen-Transplantation, autologe Chondrozytentransplantation). Die autologe Knorpel-Knochen-Transplantation ist aktuell das einzige Verfahren, das den Defekt mit hyalinem Knorpel ersetzt; problematisch sind allerdings die Entnahmemorbidität und die begrenzte Verfügbarkeit. Stammzellrekrutierende Verfahren und die autologe Knorpelzelltransplantation führen in der Regel zu einem faserknorpeligen Gewebe, das als Funktionsgewebe häufig mittelfristig gute klinische Ergebnisse liefert. Jedes dieser Therapieprinzipien hat bestimmte Indikationsschwerpunkte. Um eine adäquate Therapie zu wählen, bedarf es daher zunächst der Klassifikation des chondralen bzw. osteochondralen Schadens. Unter einer Vielzahl von Klassifikationssystemen sind besonders die Systeme der ICRS von klinischer Relevanz.

The traditional view of OA is that it is primarily a disease of articular cartilage that results, by altering the biomechanics of the joint, in secondary changes to the subchondral bone and, through secondary inflammation, other joint tissues. This focus on cartilage tends to ignore other musculoskeletal changes reported, especially those remote from affected joints. It has been proposed instead that generalized OA is a systemic musculoskeletal disorder with a metabolic component. Evidence for this position will be presented by summarizing changes identified in all the major musculoskeletal tissues. This will endeavour to show the links between these tissues, most of which have a common mesenchymal origin. Dysregulated tissue turnover, with the balance in favour of growth, will be seen to be a common thread underlying many of the changes described. It is proposed that the production of new tissue in the midst of existing tissue, in the wrong place and at the wrong time, could result in the changes observed and that reversion of cellular behaviour to an earlier, developmental-like, phenotype may provide a mechanism that could drive the disease process. New therapies may arise both from recognizing this whole musculoskeletal disease phenotype and by exploring what might be the factors underlying this cellular reversion.

Purpose: To determine the prevalence of full-thickness focal chondral defects in the athlete's knee. Methods: We conducted a systematic review of multiple databases, evaluating studies of the prevalence of articular cartilage defects in athletes. Because of the heterogeneity of data, a meta-analysis could not be performed. Results: Eleven studies were identified for inclusion (931 subjects). All studies were level 4 evidence. Defects were diagnosed via magnetic resonance imaging, arthroscopy, or both. Forty percent of athletes were professionals (NBA and NFL). The overall prevalence of full-thickness focal chondral defects in athletes was 36% (range = 2.4%-75% between all studies). Fourteen percent of athletes were asymptomatic at the time of diagnosis. Patellofemoral defects (37%) were more common than femoral condyle (35%) and tibial plateau defects (25%). Medial condyle defects were more common than lateral (68% vs 32%), and patella defects were more common than trochlea (64% vs 36%). Meniscal tear (47%) was the most common concomitant knee pathological finding, followed by anterior cruciate ligament tear (30%) and then medial collateral ligament or lateral collateral ligament tear (14%). Conclusions: Full-thickness focal chondral defects in the knee are more common in athletes than among the general population. More than one-half of asymptomatic athletes have a full-thickness defect. Further study is needed to define more precisely the prevalence of these lesions in this population.

This article outlines an approach to basic plain-film diagnosis and differential diagnosis of the arthritides. It advocates the use of an analysis of which part of the joint is involved, and works through a logical sequence to reach a final diagnosis. It recommends the concept of dividing up the arthritides into those in which the radiological effects predominantly affect synovium, cartilage or the enthesis.

Objective: Regeneration of hyaline cartilage has been the focus of an increasing number of research groups around the world. One of the most important outcome measures in evaluation of its success is the histological quality of cartilaginous tissue. Currently, a variety of histological scoring systems is used to describe the quality of osteoarthritic, in vivo repaired or in vitro engineered tissue. This review aims to provide an overview of past and currently used histological scoring systems, in an effort to aid cartilage researchers in choosing adequate and validated cartilage histological scoring systems.

For young patients with cartilage defects, the emergence of clinically applicable cell therapy for biological joint reconstruction is an appealing prospect. Acceptation of this method as a means of standard care requires proof of being reproducible, having long-lasting mechanical integrity, and having a good clinical outcome. This study evaluates the reliability of the International Cartilage Repair Society (ICRS) score and the Oswestry Arthroscopy Score (OAS) in the assessment of regenerative cartilage repair. A total of 101 macroscopic images of cartilage repair were made during arthroscopy 12 months post-treatment of either Autologous Chondrocyte Implantation (ACI) or microfracture. These images were examined by seven independent observers with differing levels of experience. The ICRS and OAS scores were randomly presented twice at a 4-week interval. All observers stated their predicted outcome according to actual treatment and defect size. ICRS and OAS scores showed both good inter- and intra observer reliability (0.62 and 0.56 for ICRS; 0.73 and 0.65 for OAS, respectively). Internal consistency (Cronbach's alpha) was satisfactory for research purposes (0.79 and 0.74, respectively). Correlation (equivalence concordance) between both scoring systems was excellent (r=0.94). All observers were inconsistent in predicting actual treatment. Test-re test reliability of estimated defect size and its correlation to true defect size were poor. These results were also applicable to the sub-analyses of the experience of the observer and the quality of imaging. The ICRS and OAS are reliable and relevant scores that are now both validated for macroscopic evaluation of cartilage repair as a research tool.