Introduction and Aims: We undertook this study to detemine the results of acetabular fixation using the Duraloc 300 uncemented acetabular component in patients with inflammatory joint disease and poor bone stock. Method: Fifty consecutive total hip replacements using a Duraloc 300 cup in patients with imflammatory joint disease were reviewed at an average of 8.2 years. Postoperative x-rays were analysed for cup placement and interface gaps. Follow-up films were analysed for lucent lines, osteolysis, wear and migration. Kaplan-Meier survivorship analysis was performed. Results: All components were found to be stable with no evidence of loosening or migration. One patient developed sepsis seven years post-surgery. There was no evidence of excessive wear or osteolysis. Conclusion: The Duraloc 300 cementless acetabular component has excellent fixation with no cases of loosening at an average of 8.2 years in patients with inflammatory joint disease. The low rate of wear and pelvic osteolysis may be indicative of the decreased demands placed on the prosthesis in this cohort of patients. The poor bone stock has not however adversely effected acetabular fixation

Aims. Machine learning (ML), a branch of artificial intelligence that uses algorithms to learn from data and make predictions, offers a pathway towards more personalized and tailored surgical treatments. This approach is particularly relevant to prevalent joint diseases such as osteoarthritis (OA). In contrast to end-stage disease, where joint arthroplasty provides excellent results, early stages of OA currently lack effective therapies to halt or reverse progression. Accurate prediction of OA progression is crucial if timely interventions are to be developed, to enhance patient care and optimize the design of clinical trials. Methods. A systematic review was conducted in accordance with PRISMA guidelines. We searched MEDLINE and Embase on 5 May 2024 for studies utilizing ML to predict OA progression. Titles and abstracts were independently screened, followed by full-text reviews for studies that met the eligibility criteria. Key information was extracted and synthesized for analysis, including types of data (such as clinical, radiological, or biochemical), definitions of OA progression, ML algorithms, validation methods, and outcome measures. Results. Out of 1,160 studies initially identified, 39 were included. Most studies (85%) were published between 2020 and 2024, with 82% using publicly available datasets, primarily the Osteoarthritis Initiative. ML methods were predominantly supervised, with significant variability in the definitions of OA progression: most studies focused on structural changes (59%), while fewer addressed pain progression or both. Deep learning was used in 44% of studies, while automated ML was used in 5%. There was a lack of standardization in evaluation metrics and limited external validation. Interpretability was explored in 54% of studies, primarily using SHapley Additive exPlanations. Conclusion. Our systematic review demonstrates the feasibility of ML models in predicting OA progression, but also uncovers critical limitations that currently restrict their clinical applicability. Future priorities should include diversifying data sources, standardizing outcome measures, enforcing rigorous validation, and integrating more sophisticated algorithms. This paradigm shift from predictive modelling to actionable clinical tools has the potential to transform patient care and disease management in orthopaedic practice. Cite this article: Bone Joint J 2024;106-B(11):1216–1222

Objective: To study the incidence of joint replacement procedure, arthrodesis, and synovectomy among patients with chronic inflammatory joint disease during the period 1994 to 2004. Methods: Data from the Norwegian Arthroplasty Register was used to find the number of joint replacement procedures performed in Norway 1994 – 2004. The incidences of arthrodeses and synovectomies were obtained from the Norwegian Patient Register. Incidence rates were calculated based on age, year, and gender specific population rates for the Norwegian population, obtained from Statistics Norway. Results: There were 8268 primary joint replacements, 3554 arthrodeses, and 5012 synovectomies performed in patients with inflammatory arthritis (IA) during the study period. A reduction in joint replacement procedures and synovectomies took place during the period 1994 to 2004, in patients with IA. For the oldest patients (80 years and older), no such trend was found. During the same time period, the incidence of joint replacements due to osteoarthritis increased. A significant reduction in the incidence of arthrodesis procedures was also found for the total study group, but not for the different subgroups. Conclusion: The incidence of joint replacements and synovectomies among patients with chronic inflammatory joint disease decreased from 1994 to 2004. This may be the result of improved medical treatment of these patients

In-vitro models of disease are valuable tools for studying disease and analysing response to therapeutics. Recently, advances in patient-derived organoid (PDO) models have been shown to faithfully recapitulate structure, function, and therapeutic response for a wide range of tissues. Frozen shoulder is a rare example of a chronic inflammatory fibrotic disease which is self-limiting, unlike many other soft tissue fibrotic disorders. As no in-vitro 3D models or in-vivo animal models exist for frozen shoulder, establishing an organoid model which recapitulates core diseases features may give insight into fibrosis resolution. Consequently, using biocompatible hydrogels, primary capsular fibroblasts, monocyte-derived macrophages and HUVEC cells, we generated stable PDO cultures which exhibited key disease phenotypes, including vascularization, increased stiffness, and an expanded lining layer over 21 days of culture. Through further investigation of cell-matrix and cell-cell interactions in the organoid model, we intend to unpack the differences between resolving and non-resolving fibrotic disease and uncover clinically relevant therapeutic targets for fibrosis.

Purpose: Arthodesis is the conventional treatment for the rheumatoid wrist. In the event of severe bilateral disease, bilateral arthrodesis can be discussed as an alternative to unilateral arthrodesis an contralateral prosthesis. We wanted to know the functional outcomes after bilateral arthrodesis. Material and methods: This retrospective analysis involved seven patients (one man and six women), mean age 46 years (28–69) who underwent total bilateral arthrodesis of the wrist for inflammatory joint disease (six rheumatoid, one chronic juvenile arthritis). Mean follow-up was five years. The patients were reviewed clinically and radiographically. We noted goniometric measurements of the upper limbs, the Jebsen hand function test (for activities of daily life), force (wrist and grip), and the Buck-Gramcko-Lohmann evaluation. Results: On average, the position achieved after arthrodesis was 2° flexion (−5° to +10°) with 6° ulnar inclination (−5° to +20°). Radiological fusion was achieved in all cases. At last follow-up, we noted that three patients had resumed their occupational activities, one had been reclassified as handicapped, and one as disabled. One patient was a housewife and one other woman was retired. The Jebsen hand test showed that our patients could perform 32 of the 49 daily activities (65%). Daily activity was noted excellent in three patients, good in two and fair in two. The Buck-Gramcko-Lohmann score was fair 6.8/10 (2–10) corresponding to good outcome. All patients were satisfied with the outcome. Discussion: Daily life activities could be performed readily after bilateral arthrodesis of the wrist. Perineal hygiene was possible for five of our patients. The only problems concerned activities requiring force and fine movements, because of the apprehension and the lack of fine dexterity. Poor results could be attributed to metacarpophalangeal deformations and decreased grip force. We observed an 80% reduction in force compared with a representative population of non-operated patients with rheumatoid disease. Bilateral arthrodesis is a valid alternative to bilateral arthroplasty or combined arthrodesis prosthesis implantation. It does not expose the patients to the risk of mechanical arthroplasty

Aims

The aim of this study was to explore the genetic correlation and causal relationship between blood plasma proteins and rheumatoid arthritis (RA).

Aims

Metabolic profiling is a top-down method of analysis looking at metabolites, which are the intermediate or end products of various cellular pathways. Our primary objective was to perform a systematic review of the published literature to identify metabolites in human synovial fluid (HSF), which have been categorized by metabolic profiling techniques. A secondary objective was to identify any metabolites that may represent potential biomarkers of orthopaedic disease processes.

Osteoarthritis (OA) is one of the most prevalent diseases of the elderly, affecting greater than 50% of the population over 60 years of age. Many factors are implicated in the development of OA but currently no mechanism has been described that provides an explanation for age as the major risk factor for OA. The present studies were designed to investigate the hypothesis that age-related accumulation of advanced glycation endproducts (AGEs) provides a molecular mechanism that explains (at least in part) the age-related increase in the incidence of OA.

To gain insight in the diversity of AGEs present in articular cartilage, several AGE measures were determined in a wide age-range of normal human articular cartilage samples: all demonstrated increased AGE levels with increasing age. The level of these AGEs was high in cartilage compared to other tissues such as skin, which is mainly caused by the very low turnover of the cartilage matrix proteins. The t1/2 of collagen in articular cartilage is ~117 years (compared to t1/2 of skin collagen of ~15 years).

Accumulation of AGEs in cartilage affected biomechanical, biochemical and cellular characteristics of the tissue. At the biomechanical level, increased AGE levels were accompanied by increased stiffness and brittleness, indicating that AGE accumulation leads to increased susceptibility of articular cartilage to mechanical damage. On the cellular level, accumulation of AGEs decreased the synthesis and degradation (= turnover) of the cartilage matrix. Such decreased cartilage turnover is likely to result in decreased repair capacity of the tissue.

In combination, the AGE-related increase in tissue brittleness and decrease in extracellular matrix turnover, results in articular cartilage that is more prone to damage. This concept, that AGE accumulation predisposes to the development of OA was tested in the canine anterior cruciate ligament transection (ACLT) model for osteoarthritis. Selectively enhancing AGE levels in articular cartilage of young animals (in the absence of other age-related changes) resulted in more severe OA.

Altogether, AGE accumulation in articular cartilage presents a molecular mechanism by which ageing predisposes to the development of OA, and it provides new possibilities for prevention and/or therapy via the inhibition and/or reversal of cartilage AGE formation.

Aims: The purpose of this presentation is to discuss what population interventions are effective, what the evidence for the different interventions for the different conditions is and how one can identify those who will benefit most. Methods: Evidence of effective interventions for primary, secondary and tertiary prevention of the individual conditions has been identified from systematic reviews and guidelines through literature review. From this and expert opinion, recommendations have been developed which follow a template to enable common themes appropriate to the different musculo-skeletal conditions to emerge. Results: Common factors with an effect on the population level on different musculoskeletal conditions include exercise, body weight, diet, smoking, alcohol and occupational factors. One specific factor is injury prevention including falls to prevent osteoporotic fractures. One recommendation supported by evidence that applies to all conditions considered is the need for early appropriate intervention for those at highest risk or with early features of the condition. Evidence for the different interventions for the conditions will be presented Conclusions: Prevention of musculoskeletal conditions on a population level is possible. If risk factors for the different conditions are identified, development of effective interventions is necessary.

Aims: The purpose of this presentation is to discuss what population interventions are effective, what the evidence for the different interventions for the different conditions is and how one can identify those who will benefit most. Methods: Evidence of effective interventions for primary, secondary and tertiary prevention of the individual conditions has been identified from systematic reviews and guidelines through literature review. From this and expert opinion, recommendations have been developed which follow a template to enable common themes appropriate to the different musculoskeletal conditions to emerge. Results: Common factors with an effect on the population level on different musculoskeletal conditions include exercise, body weight, diet, smoking, alcohol and occupational factors. One specific factor is injury prevention including falls to prevent osteoporotic fractures. One recommendation supported by evidence that applies to all conditions considered is the need for early appropriate intervention for those at highest risk or with early features of the condition. Evidence for the different interventions for the conditions will be presented Conclusions: Prevention of musculoskeletal conditions on a population level is possible. If risk factors for the different conditions are identified, development of effective interventions is necessary.

The decision to undertake total hip replacement (THA) in a child is complex and daunting. This is augmented by the paucity of data on potential quality of life (QoL) improvement and functional outcomes. Therefore, the aim of this study was to ascertain whether outcomes after surgery are influenced by the nature of the primary diagnosis. This was a prospective, consecutive cohort study of patients under the age of 18 years undergoing THA by a single arthroplasty surgeon in collaboration with colleagues at a regional paediatric hospital. Patient electronic notes, radiographs and PROMS (EQ5D-Y, Oxford Hip Score (OHS) and modified Harris Hip Score(mHHS)) were reviewed. Twenty-two THAs were performed in patients less than 18 years (median 15 (range 10.7–17.9), with 7 patients undergoing bilateral surgery. Mean follow-up was 2 years. Thirteen of the THAs were undertaken for systemic conditions effecting multiple joints (Mucopolysaccharidoses, Mucolipidosis and Scwachman-Diamond syndrome) with the hip the worst affected joint and 9 for single joint disease (AVN, Perthes, dysplasia and idiopathic chondrolysis). PROMS scores showed reliable improvements with no differences between the two groups. Health related QoL was calculated from EQ5D-Y and indicated an overall improvement of 1.06(0.879–1.25). 6 patients were wheelchair users preop. All patients were independent walkers at follow-up. One patient underwent successful revision surgery for aseptic acetabular loosening. There were no other complications. THA in children leads to a significant positive impact on QoL as measured with validated PROMS scores. Patients with systemic conditions can benefit just as much as those with single joint disease. Further follow-up is required to understand the long-term outcomes

Aims. Osteoarthritis (OA) is a prevalent joint disorder with inflammatory response and cartilage deterioration as its main features. Dihydrocaffeic acid (DHCA), a bioactive component extracted from natural plant (gynura bicolor), has demonstrated anti-inflammatory properties in various diseases. We aimed to explore the chondroprotective effect of DHCA on OA and its potential mechanism. Methods. In vitro, interleukin-1 beta (IL-1β) was used to establish the mice OA chondrocytes. Cell counting kit-8 evaluated chondrocyte viability. Western blotting analyzed the expression levels of collagen II, aggrecan, SOX9, inducible nitric oxide synthase (iNOS), IL-6, matrix metalloproteinases (MMPs: MMP1, MMP3, and MMP13), and signalling molecules associated with nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. Immunofluorescence analysis assessed the expression of aggrecan, collagen II, MMP13, and p-P65. In vivo, a destabilized medial meniscus (DMM) surgery was used to induce mice OA knee joints. After injection of DHCA or a vehicle into the injured joints, histological staining gauged the severity of cartilage damage. Results. DHCA prevented iNOS and IL-6 from being upregulated by IL-1β. Moreover, the IL-1β-induced upregulation of MMPs could be inhibited by DHCA. Additionally, the administration of DHCA counteracted IL-1β-induced downregulation of aggrecan, collagen II, and SOX9. DHCA protected articular cartilage by blocking the NF-κB and MAPK pathways. Furthermore, DHCA mitigated the destruction of articular cartilage in vivo. Conclusion. We present evidence that DHCA alleviates inflammation and cartilage degradation in OA chondrocytes via suppressing the NF-κB and MAPK pathways, indicating that DHCA may be a potential agent for OA treatment. Cite this article: Bone Joint Res 2023;12(4):259–273

Osteoarthritis (OA) is the most common joint disease, affecting approximately 16% of the adult population worldwide. The chronic inflammation in the joint leads to the breakdown of cartilage, which leads to permanent pain and limitations in everyday life at an early stage of the disease. To date, there is no therapy that can interrupt the inflammatory state or reverse cartilage damage. The PROTO consortium (funded by the EU Horizon Europe program, Grant 101095635) aims to prevent the development of OA by correcting a pathological biomechanical pattern by a digital training intervention and to treat early stage OA with an innovative allogeneic cell therapy

Aims. Hereditary haemochromatosis is a genetic disorder that is caused by several known mutations in the human homeostatic iron regulator protein (HFE) gene. Abnormal accumulation of iron causes a joint disease that resembles osteoarthritis (OA), but appears at a relatively younger age and is accompanied by cirrhosis, diabetes, and injury to other organs. Increased serum transferrin saturation and ferritin levels are known markers of haemochromatosis with high positive predictive values. Methods. We have retrospectively analyzed the iron studies of a cohort of 2,035 patients undergoing knee joint arthroplasty due to OA. Results. No patients had HFE gene C282Y, S65C, or H63D mutations testing. In total, 18 patients (2.96%) of the male cohort and 51 (3.58%) of the female cohort had pathologically increased ferritin levels that may be indicative of haemochromatosis. Seven patients (0.34%) had serum transferrin saturation above 45%. Conclusion. The awareness for the diagnosis of this disorder in Orthopaedics is low and needs improvement. Osteoarthritic patients undergoing knee arthroplasty should be routinely screened for haemochromatosis by iron studies and referred to genetic testing when needed. Level of evidence: Level III - Retrospective cohort study. Cite this article: Bone Jt Open 2021;2(12):1062–1066

Osteoarthritis (OA), the most prevalent chronic joint disease, represents a relevant social and economic burden worldwide. Human umbilical cord mesenchymal stem cells (HUCMSCs) have been used for injection into the joint cavity to treat OA. The aim of this article is to clarify whether Huc-MSCs derived exosomes could inhibit the progression of OA and the mechanism in this process. A rabbit OA model was established by the transection of the anterior cruciate ligament. The effects of HUCMSCs or exosomes derived from HUCMSCs on repairing articular cartilage of knee osteoarthritis was examined by micro-CT. Immunohistochemical experiments were used to confirm the expression of relevant inflammatory molecules in OA. In vitro experiments, Transwell assay was used to assess the migration of macrophages induced by TNF-a. Results showed that a large number of macrophages migrated in arthcular cavity in OA model in vivo, while local injection of HUCMSCs and exosomes did repair the articular cartilage. Immunohistochemical results suggested that the expression of CCL2 and CD68 in the OA rabbit model increased significantly, but was significantly reduced by HUCMSCs or exosomes. Transwell assay showed that both HUCMSCs and exosomes can effectively inhibit the migration of macrophage. In conclusion, the exosomes derived by HUCMSCs might might rescue cartilage defects in rabbit through its anti-inflammatory effects through inhibiting CCL2

Osteoarthritis (OA) of the knee joint is a complex peripheral joint disorder with multiple risk factors. We aimed to examine the relationship between the grade of knee OA and anterior thigh length (ATL). A total of 64 geriatric patients who had no total hip or knee replacement with a BMI of ≥30 were evaluated. Patients' OA severity was determined by two independent experts from bilateral standing knee radiographs according to the Kellgren-Lawrence (KL) grade. Joint cartilage structure was assessed using ultrasonography (US). The ATL, the gastrocnemius medialis (GC), the rectus femoris (RF) and the rectus abdominis (RA) skeletal muscle thicknesses as well as the RF cross-sectional area (CSA) were measured with US. Sarcopenia was diagnosed using the handgrip strength (HGS), 5× sit-to-stand test (5xSST) and bioelectrical impedance analysis. The median (IQR) age of participants was 72 (65–88) years. Seventy-one per cent of the patients (n=46) were female. They were divided into the sarcopenic obese (31.3 %) and the non-sarcopenic obese (68.8%) groups. KL grade of all patients correlated negatively with the ATL (mm) and the thickness of GC (mm) (r= -0,517, p<0.001 and r= -0.456, p<0.001, respectively). In the sarcopenic obese and the non-sarcopenic obese groups, KL grade of the all patients was negatively correlated with ATL (mm) and thickness of GC (mm) (r= -0,986, p<0.001; r= -0.456, p=0.05 and r= -0,812, p=0.002; r= −0,427, p=0.006). KL grade negatively correlated with the RF thickness in the sarcopenic obese group (r= -0,928, p=0.008). In conclusion, OA risk may decrease as the lower extremity skeletal muscle mass increases. Acknowledgments: Feza Korkusuz MD is a member of the Turkish Academy of Sciences (TÜBA)

Reverse Total shoulder arthroplasty (RTSA) was initially introduced to treat rotator cuff arthropathy. With proven successful long-term outcomes, it has gained a noteworthy surge in popularity with its indications consequently being extended to treating various traumatic glenohumeral diseases. Several countries holding national registries remain a guide to the use the prosthesis, however a notable lack of epidemiological data still exists. More so in South Africa where the spectrum of joint disease related to communicable diseases such as HIV and tuberculosis may influence indications and patient demographics. By analysing the epidemiology of patients who underwent RTSA at our institution, we aimed to outline the local disease spectrum, the patients afflicted and indications for surgery. A retrospective review of all patients operated within the sports unit between 1 January 2019 and 31 December 2022 was conducted. An analysis of the epidemiological data pertaining to patient demographics, diagnosis, indications for surgery and complications were recorded. Included in the review were 58 patients who underwent primary RTSA over the 4-year period. There were 41 females and 17 male patients, age <55 years (n= 14) >55 years (n=44). The indications included 23 rotator cuff arthropathy (40%), 12 primary glenohumeral osteoarthritis (OA) (20%), 10 avascular necrosis (AVN) humeral head (17%), 7 inflammatory OA (12%), 4 chronic shoulder dislocation (7%) and 2 sequalae of proximal humerus fractures (4%). The study revealed RTSA being performed in patients older than 55 years of age, the main pathologies included rotator cuff arthropathy and primary OA, however AVN and shoulder dislocations secondary to trauma contributed significantly to the total tally of surgeries undertaken. This highlights the disease burden of developing countries contributing to patients presenting for RTSA

Osteochondrosis (OC) is a common joint disease that affects developing cartilage and subchondral bone in humans, and in multiple animal species including horses. It is an idiopathic localized joint disorder characterized by focal chondronecrosis and retention of growing cartilage that can lead to the formation of fissures, subchondral bone cysts or intra-articular fragments. OC is considered a complex multifactorial disease with chondrocyte biogenesis impairment mainly due to biochemical and genetic factors. Likewise, the molecular events involved in the OC are not fully understood. Moreover, the OC pathogenesis seems to be shared across species. In particular, equine OC and human juvenile OC share some symptoms, predilection sites and clinical presentation. In this study, by using the label-free mass spectrometry approach, proteome of chondrocytes isolated from equine OC fragments has been analysed in order to clarify some aspects of cell metabolism impairment occurring in OC. Equine chondrocytes isolated from 7 healthy articular cartilages (CTRL) and from 7 osteochondritic fragments (OC) (both obtained from metacarpo/metatarsophalangeal joints) were analysed. Proteins were extracted using urea and ammonium bicarbonate buffer, reduced, alkylated and digested with Trypsin/Lys-C Mix. Peptides were analysed using Q Exactive UHMR Hybrid Quadrupole-Orbitrap Mass Spectrometer (Thermo Scientific). All mass spectra of label-free samples analysed was set up to search against SwissProt human database (Homo sapiens) and SwissProt horse database (Equus caballus). One-way ANOVA was used for hypothesis testing. Proteins with a ≥1.5 fold change and with a FDR adjusted p value of ≤0.05 were defined as differentially expressed. Statistical analysis evidenced 41 proteins up-regulated in OC while 18 were down-regulated with respect to the CTRL. Functional analysis showed that up-regulated proteins in OC were related to extracellular matrix degradation, lysosome, apoptotic execution phase, unfolded protein response, hyaluronan and keratan sulfate degradation, oxidative stress response and negative regulation of BMP signalling pathway. The down-regulated proteins were associated with endochondral ossification, vitamin D in inflammatory disease, Wnt signalling pathway and ECM proteoglycans. Validation assays confirmed these findings. These findings may contribute to clarify the events determining the onset and progression of both equine and human OC. Imaging MS analysis of OC and healthy cartilage to analyse lipid and metabolomic changes occurring in OC cartilage is in progress

Primary total joint arthroplasty (TJA) is an increasingly common and safe way of treating joint disease. Robust preoperative assessment improved intraoperative techniques and holistic rehabilitation contribute to an uneventful postoperative period. Despite there being evidence against the utility of postoperative blood tests, it is still often part of routine practice. We aim to evaluate the usefulness of these tests by investigating their incidence following TJA as well as identifying preoperative risk factors for abnormal blood test results postoperatively especially pertaining to anaemia and acute kidney injury (AKI). This is a retrospective cohort study of patients who had elective TJA between January and December 2019 at a tertiary centre. An independent student's t-test and Fisher's exact test was used to compare variables between the normal and abnormal postoperative results groups. An analysis of variance (ANOVA) was performed to identify risk factors for an abnormal blood test result. Analyses of receiver operating characteristic (ROC) curves and the area under the curve (AUC) were used to determine cut off values that could be suggestive of abnormal test results postoperatively. The study included 2721 patients with a mean age of 69 of which 46.6% were males. Abnormal postoperative bloods were identified in 444 (16.3%) patients. We identified age (≥65 years), female gender, ASA ≥ 3 as risk factors for developing abnormal postoperative blood tests. Preoperative haemoglobin (≤ 127 g/dL), haematocrit (≤ 0.395L/L) and potassium (≤ 3.7 mmol/L) were noted as cut-offs that could be predictive of postoperative anaemia or AKI respectively. The costs outweigh the benefits of ordering routine postoperative blood tests in TJA patients. Clinicians should risk stratify their patients and have a lower threshold for ordering blood tests in patients with one or more of the risk factors we have identified. These risk factors are age (≥65 years), females, ASA ≥ 3, preoperative haemoglobin (≤ 127 g/L), haematocrit (≤ 0.395L/L), and potassium (≤ 3.7 mmol/L)

Hip Osteoarthritis (HOA) is the most common joint disorder and a major cause of disability in the adult population, leading to total hip replacement (THR). Recently, evidence has mounted for a prominent etiologic role of femoroacetabular impingement (FAI) in the development of early OA in the non-dysplastic hip. FAI is a pathological mechanical process, caused by abnormalities of the acetabulum and/or femur leading to damage the soft tissue structures. FAI can determine chondro-labral damage and groin pain in young adults and can accelerate HOA progression in middle-aged adults. The aim of the study was to determine if the presence of calcium crystal in synovial fluid (SF) at the time of FAI surgery affects the clinical outcomes to be used as diagnostic and predictive biomarker. 49 patients with FAI undergoing arthroscopy were enrolled after providing informed consent; 37 SFs were collected by arthrocentesis at the time of surgery and 35 analyzed (66% males), median age 35 years with standard deviation (SD) 9.7 and body mass index (BMI) 23.4 kg/m. 2. ; e SD 3. At the time of surgery, chondral pathology using the Outerbridge score, labral pathology and macroscopic synovial pathology based on direct arthroscopic visualization were evaluated. Physical examination and clinical assessment using the Hip disability & Osteoarthritis Outcome Score (HOOS) were performed at the time of surgery and at 6 months of follow up. As positive controls of OA signs, SF samples were also collected from cohort of 15 patients with HOA undergoing THR and 12 were analysed. 45% FAI patients showed CAM deformity; 88% presented labral lesion or instability and 68% radiographic labral calcification. 4 patients out of 35 showed moderate radiographic signs of OA (Kellegren-Lawrence score = 3). Pre-operative HOOS median value was 61.3% (68.10-40.03) with interquartile range (IQR) of 75-25% and post-operative HOOS median value 90% with IQR 93.8-80.60. In both FAI and OA patients the calcium crystal level in SFs negatively correlated with glycosaminoglycan (component of the extracellular matrix) released, which is a marker of cartilage damage (Spearman rho=-0.601, p<0.001). In FAI patients a worst articular function after surgery, measured with the HOOS questionnaire, was associated with both acetabular and femoral chondropathy and degenerative labral lesion. Moreover, radiographic labral calcification was also significantly associated with pain, worst articular function and labral lesion. Calcium crystal level in SFs was associated with labral lesions and OA signs. We concluded that the levels of calcium crystals in FAI patients are correlated with joint damage, OA signs and worst post-operative outcome. The presence of calcium crystals in SF of FAI patients might be a potential new biomarker that might help clinicians to make an early diagnosis, evaluate disease progression and monitor treatment response