2023 American College of Rheumatology and American Association of Hip and Knee Surgeons Clinical Practice Guideline for the Optimal Timing of Elective Hip or Knee Arthroplasty for Patients With Symptomatic Moderate-to-Severe Osteoarthritis or Advanced Symptomatic Osteonecrosis With Secondary Arthritis for Whom Nonoperative Therapy Is Ineffective

Primary Total Knee Arthroplasty in Patients with BMI of ≥50 kg/m2: A Cohort Study with Long-Term Follow-up

BACKGROUND

The obesity epidemic has given rise to an orthopaedic patient subgroup with a body mass index (BMI) of ≥50 kg/m2. Without sound evidential guidance, arthroplasty surgeons and anesthesiologists do not know whether they can push the limits of the surgical feasibility of total knee arthroplasty (TKA) without risks of harm.

METHODS

In a retrospective cohort study of patients who had undergone primary TKA for degenerative arthritis at our academic center (n = 10,389; 6,821 women, 4,070 men, and 38 unknown), we compared the outcomes between patients with a BMI of ≥50 kg/m2 (n = 627) and patients in other weight classes. The average patient follow-up was 8.6 years. We used Cox proportional hazards models to estimate the association between BMI and revision risk, using overweight patients (BMI = 25 to 29.99 kg/m2) as the reference group while adjusting for patient age and sex. Patient satisfaction, pain scores on a visual analogue scale (VAS), and the Oxford Knee Score (OKS) were compared among groups preoperatively and at 1, 5, and 10 years postoperatively.

RESULTS

In the first year after surgery, the adjusted hazard ratio (HR) for revision TKA for patients with a BMI of ≥50 kg/m2 was 3.7 (95% confidence interval [CI] = 1.9 to 7.2), with overweight patients as the reference. There was virtually no difference between patients with a BMI of 35 to 39.99 kg/m2 and those with a BMI of 40 to 49.99 kg/m2. After the first year, the HR was 1.2 (95% CI = 0.7 to 2.4) for revision TKA for patients with a BMI of ≥50 kg/m2. Those patients reported worse preoperative function of the knee, with a median OKS of 15 versus 23 for overweight patients. For obese patients, each additional unit of BMI corresponded with an additional OKS improvement of 0.07 point (95% CI = 0.04 to 0.10) at 1 year.

CONCLUSIONS

Our study confirms the increased risk of failure of TKA in patients with a BMI of ≥50 kg/m2 in the first year after surgery, but we found no evidence of worse outcomes in the 40 to 49.99 kg/m2 group compared with the 35 to 39.99 kg/m2 group. The increase in the revision risk in the ≥50 kg/m2 group was found only in the first postoperative year and plateaued afterwards. Despite worse function and higher failure rates, patients with a BMI of ≥50 kg/m2 reported benefits and high satisfaction with TKA.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Factors associated with high hidden blood loss in patients undergoing primary total knee arthroplasty for osteoarthritis: a cross-sectional retrospective study of 1444 patients

PURPOSE

Total knee arthroplasty (TKA) can cause significant hidden blood loss after surgery, and transfusion or erythropoietin (EPO) treatment may be required. This study aimed to identify the factors associated with blood loss in patients undergoing TKA for osteoarthritis (OA).

METHODS

We retrospectively enrolled 1444 OA patients undergoing primary TKA from January 2022 to June 2024. The patients were divided into two groups according to the grade of hidden blood loss. To identify the key influencing factors, we conducted a logistic regression analysis.

RESULTS

This study analyzed 1,444 primary arthroplasty cases, identifying 236 patients with high hidden blood loss (HHBL). Coronary artery disease (CAD) was significantly more prevalent in the HHBL group (15.3% vs. 9.4%, p = 0.006). Preoperative EPO use was higher in the low hidden blood loss (LHBL) group (21.9% vs. 9.3%, p < 0.001). Significant preoperative lab differences included hemoglobin, hematocrit, and platelet count. Surgical factors associated with HHBL included left knee TKA, conventional mechanical TKA (CMTKA), longer operation times, and intraoperative blood loss (IBL) > 20%. Postoperatively, the HHBL group had significantly more transfusions and longer hospital stays. Logistic regression identified CAD, platelet count, left knee surgery, CMTKA, operation time, and preoperative EPO use as significant factors influencing HHBL. These findings highlight the need for targeted strategies to manage blood loss in knee arthroplasty patients.

CONCLUSIONS

This study identifies several factors associated with high hidden blood loss in patients undergoing TKA for osteoarthritis. CAD, CMTKA, prolonged operation time, left-sided surgery, lower preoperative platelet count, and lack of preoperative erythropoietin (EPO) use were significantly linked to HHBL. While these associations highlight potential targets for intervention, further prospective studies are needed to confirm causality.

[Influence of obesity on midterm outcome after primary hip and knee arthroplasty in Germany : Analysis from the EPRD]

OBJECTIVES

To determine the influence of obesity on revision rates and mortality after primary elective hip and knee arthroplasty in Germany.

MATERIALS AND METHODS

In the German Arthroplasty Registry (EPRD) there were 403,073 elective total hip arthroplasties (THA), 320,913 bicondylar total knee arthroplasties (TKA) and 48,480 unicondylar knee arthroplasties (UKA) with valid BMI available for analysis. Cumulative revision rates and 1‑year mortality was calculated for BMI groups.

RESULTS

There were increased revision rates with increasing BMI, most distinctive for septic revisions in THA during the first year after surgery (non-obese 0.7%, obesity grade 1 1.3%, grade 2 2.1%, grade 3 4.2%). In TKA and UKA this increase was generally less pronounced. Age- and gender-standardized mortality was lower than expected in most groups, but also increasing with increasing BMI.

CONCLUSION

The risk for revisions in obese patients is more distinctive in hip arthroplasty than in knee arthroplasty and is especially high in morbidly obese patients (BMI ≥ 40 kg/m2). Nonetheless, this risk may be acceptable for affected patients. Therefore, the possible benefits and risks of an arthroplasty should be weighed against each other and individually discussed with the patient.

[Current AWMF guidelines on knee and hip arthroplasty - individual risks]

BACKGROUND

In the year 2022, more than 300,000 total hip and knee primary arthroplasties were recorded in the German Arthroplasty Registry. The ever-increasing number of interventions naturally leads to an increase in the absolute number of possible complications. The abundance of internationally available data makes it possible to determine risk factors for postoperative complications.

RISK FACTORS

Professional societies involved in the German guidelines in the field of orthopedics place great emphasis on modifiable risk factors, as their adequate management can consequently reduce the likelihood of postoperative complications. One of the most common modifiable risk factors is obesity, with its prevalence remaining consistently high in most developed countries. In the field of orthopedics, the Association of the Scientific Medical Societies in Germany focuses on modifiable risk factors including obesity, diabetes mellitus and smoking.

OBESITY

In the case of obesity in particular, the guidelines for knee and hip arthroplasty recommend a weight loss attempt for patients with a BMI > 30 kg/m2. A BMI ≥ 40 kg/m2 is considered a "relative contraindication" in the guidelines. Shared decision making is emphasized in both guidelines. Ultimately, the particularly critical individual assessment of risk and benefit for each obese patient remains crucial for the final decision.

Evidence-based joint statement position of perioperative bone optimization in the arthroplasty candidate, from FEMECOT, AMMOM, ACOMM, SCCOT, SECOT, SEFRAOS, SEIOMM

BACKGROUND

The prevalence of patients living with joint replacements is increasing. Nearly two-thirds of patients undergoing elective arthroplasty procedures have low bone mineral density (LBMD), defined as osteopenia in 38.5% and osteoporosis in 24.8%; among those with osteoporosis, only 32.8% received treatment at the time of surgery.

MATERIALS AND METHODS

A group of 7 national societies (FEMECOT, AMMOM, ACOMM, SCCOT, SECOT, SEFRAOS, SEIOMM) developed a joint statement position on the diagnosis of osteoporosis and perioperative bone optimization in candidates for arthroplasty "Arthroplasty Bone Optimization." We performed a scoping review of the available literature, followed by a systematic review and meta-analysis. Subsequently, a Delphi-modified method was used to gather the different positions.

RESULTS

After analyzing the literature, we came up with five recommendations: (1) Patients scheduled for elective arthroplasty should undergo a bone health assessment (BHA). (2) If poor bone quality is observed during surgery and a bone health assessment has not been conducted promptly, a complete BHA, including a DXA scan, is imperative. (3) In the arthroplasty candidate, if LBMD or osteoporosis are noticed, bone loss-related factors should be corrected, and appropriate treatment for osteoporosis should be started before or right after arthroplasty. The use of anti-resorptive and bone anabolic agents has been shown to reduce periprosthetic bone loss, complications, and non-septic revision rates after joint arthroplasty. (4) In arthroplasty candidates, the diagnosis of osteoporosis or low bone mineral density (LBMD) should not delay the surgery. (5) Monitoring central and periprosthetic bone mineral density through DXA protocols can help identify bone loss in central and periprosthetic areas in patients with risk factors or osteoporosis.

CONCLUSIONS

Perioperative bone optimization should be considered in all patients who are candidates for arthroplasty. The orthopedic surgeon and multidisciplinary team should be encouraged to diagnose and treat the arthroplasty candidates' bone by screening for bone loss-related factors and diagnosing osteoporosis and starting treatment according to the current international guidelines. Following these recommendations could reduce periprosthetic bone loss, complications, and aseptic revision rates following arthroplasty surgery. More research is needed to understand the implications of osteoporosis and its treatment for joint replacement outcomes and long-term survival.

Glucagon-Like Peptide-1 Receptor Agonists Decrease Medical and Surgical Complications in Morbidly Obese Patients Undergoing Primary TKA

BACKGROUND

Weight optimization methods in morbidly obese patients with a body mass index (BMI) of ≥40 kg/m 2 undergoing total knee arthroplasty (TKA) have shown mixed results. The purpose of this study was to evaluate the effect of perioperative use of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) in patients with a BMI of ≥40 kg/m 2 undergoing primary TKA.

METHODS

Using an administrative claims database, patients with morbid obesity undergoing primary TKA were stratified into GLP-1 RA use for 3 months before and after the surgical procedure (treatment group) and GLP-1 RA non-use (control group), and were matched on the basis of patient age, gender, diagnosis of type-2 diabetes mellitus, and Charlson Comorbidity Index (CCI). In addition, these groups were compared with a contemporaneous cohort of patients undergoing TKA with a BMI of 35.0 to 39.9 kg/m 2 . Outcomes including infection, complications, revision, and readmission were compared between the matched cohorts.

RESULTS

There were significant decreases in the rates of 90-day periprosthetic joint infection (PJI) (1.0% compared with 1.8%; p = 0.037), any medical complications (10.6% compared with 12.7%; p = 0.033), pulmonary embolism (<0.4% compared with 0.6%; p = 0.050), and readmissions (5.3% compared with 8.9%; p < 0.001) in patients with a BMI of ≥40 kg/m 2 who were taking GLP-1 RA versus the control group who were not. There were no differences in the 2-year rates of surgical complications (p > 0.05) between these groups. Compared with obese patients (BMI of 35.0 to 39.9 kg/m 2 ), patients who had a BMI of ≥40 kg/m 2 and were taking a GLP-1 RA did not have increased rates of infection or 90-day or 2-year complications (p > 0.05).

CONCLUSIONS

GLP-1 RA administration for at least 90 days prior to and after primary TKA in patients with a BMI of ≥40 kg/m 2 was associated with reductions in the risks of 90-day PJI, any medical complications, and readmission. Additionally, the reduced complication rate that was achieved was similar to that of obese patients with a BMI of 35.0 to 39.9 kg/m 2 undergoing TKA. Randomized clinical trials are needed to define the true effect of these agents on clinical outcomes following TKA.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Avascular necrosis in pediatric rheumatic diseases: an Italian retrospective multicentre study

BACKGROUND

Atraumatic avascular necrosis (AVN) is a severe condition that may complicate the course of rheumatic diseases and contribute to long-term damage. However, there is a lack of evidence on this rare event in pediatric rheumatology. The aim of our study was to evaluate the occurrence of avascular necrosis in the context of rheumatologic diseases in Italy and to describe the main demographic and clinical features of AVN patients, with a particular focus on treatment background.

METHODS

All centres part of the Italian Society of Pediatric Rheumatology were invited to participate in a retrospective case collection of children with rheumatic diseases complicated by a pediatric-onset AVN. Demographic, clinical, laboratory and imaging data were recorded, together with outcome and treatment background, particularly steroid exposure. Population collected was further evaluated according to the different underlying rheumatologic disease and to the time of AVN onset.

RESULTS

Fourteen patients (SLE = 7; JIA = 4; others = 3) were collected from 7 centres. Females were predominantly affected (71%) with a median age at AVN diagnosis of 14.3 years. Multifocal involvement was mostly reported (93%), mainly involving femoral heads (44%) and knees (28%). All patients had a severe rheumatologic background and received systemic glucocorticoids with a median cumulative prednisone equivalent dose of 457.5 mg/kg. In all patients but one imaging showed persistence of abnormalities, despite the complete resolution of symptoms in 6 of them. Bisphosphonates were the most used therapeutic approach; orthopedic surgery was required in 2 cases.

CONCLUSIONS

Despite its rarity, AVN may be a severe complication of pediatric rheumatic diseases. Active monitoring is crucial to promptly identify patients and to prevent long-term damage. Prospective large sample studies are required to better understand the impact of steroid exposure and its complex interplay with other potential contributing factors.

Design features of the rotating head total hip arthroplasty by Weber-Huggler- a forgotten technical solution to reduce wear

Total hip arthroplasty (THA) is a very successful operation. Once the problem of implant fixation was solved with the use of bone cement, the next development steps focused on improving the bearing. Weber, a Swiss surgeon, introduced the first modular heads in THA. His design improved reconstruction of the patients' anatomy using various neck lengths, eased revision as well-fixed stems could be preserved, and also reduced wear due to a cylindrical, rotating connection between the head and neck. The features and results of this exceptional design are reviewed. However, as newer material combinations greatly mitigated the problem of wear and as the dimensions of the cylindrical connection limit range of motion, it was supplanted by the nowadays well-established Morse taper connection, which also is less complex to manufacture. As Weber's design was associated with good long-term results, the technical features of this technical solution should not be forgotten.

Decreased Risk of Readmission and Complications With Preoperative GLP-1 Analog Use in Patients Undergoing Primary Total Joint Arthroplasty

BACKGROUND

There has been considerable interest in the use of GLP-1 receptor analogs (GLP-1 RAs) for weight optimization in patients undergoing elective arthroplasty. As there is limited data regarding the implications of their use, our study aimed to evaluate the association between preoperative GLP-1 RA use and postoperative outcomes in patients undergoing primary total hip arthroplasty (THA) and total knee arthroplasty (TKA).

METHODS

The TrinetX research network was queried to identify all patients undergoing primary THA or TKA between May 2005 and December 2023 across 84 health care organizations. Patients were stratified based on preoperative GLP-1 RA use. Propensity score matching (1:1) was performed to account for baseline differences in demographics, laboratory investigations, and comorbidities. Subsequently, risk ratios were evaluated for postoperative outcomes.

RESULTS

A total of 268,504 and 386,356 patients underwent THA and TKA, of which 1,044 and 2,095 used preoperative GLP-1 RAs. After matching, GLP-1 RA use was associated with a decreased 90-day risk of periprosthetic joint infection (2.1 versus 3.6%, RR = 0.58, P = .042) and readmission (1.1 versus 2.0%, RR = 0.53, P = .017) following THA and TKA, respectively. There was no difference in the risk of all other outcomes between comparison groups.

CONCLUSIONS

Preoperative GLP-1 RA use is associated with a 42% decreased risk of periprosthetic joint infection and 47% decreased risk of readmission in the 90-day postoperative period following THA and TKA, respectively, with no difference in other risks, including aspiration. Our findings indicate that GLP-1 RAs may be safe to use in patients undergoing elective arthroplasty; however, further studies are warranted to inform the routine use of GLP-1 RAs for weight management in THA and TKA patients.

Substantial Weight Loss May Not Improve Early Outcomes of Total Knee Arthroplasty in the Morbidly Obese

BACKGROUND

Body mass index (BMI) cutoffs for morbidly obese patients otherwise indicated for total knee arthroplasty (TKA) have been widely proposed and implemented, though they remain controversial. Previous studies suggested that a 5% reduction in BMI may be associated with fewer postoperative complications. Thus, the purpose of this study was to determine whether a substantial reduction in preoperative BMI in morbidly obese patients improved 90-day outcomes after TKA.

METHODS

There were 1,270 patients who underwent primary TKA at a single institution and had a BMI > 40 recorded during the year prior to surgery. Patients were stratified into three cohorts based on whether their BMI within 3 months to 1 year preoperatively had decreased by ≥ 5% (228 patients [18%]); increased by ≥ 5% (310 [24%]); or remained unchanged (within 5%) (732 [58%]) on the day of surgery. There were several baseline differences between the cohorts with respect to medical comorbidities. The rate of 90-day complications and six-week patient-reported outcome measures were compared via univariate and multivariable analyses.

RESULTS

On univariate analysis, individual and total complication rates were similar between the cohorts (P > .05). On multivariable logistic regression, the risk of complications was similar in patients who had decreased versus unchanged BMI (OR [odds ratio] 1.0; P = .898). However, there was a higher risk of complications in the increased BMI cohort compared to those patients who had an unchanged BMI (OR 1.5; P = .039). The six-week patient-reported outcome measures were similar between the cohorts.

CONCLUSIONS

Patients who have a BMI > 40 who achieved a meaningful reduction in BMI prior to TKA did not have a lower rate of 90-day complications than those whose BMI remained unchanged. Furthermore, considering that nearly one in four patients experienced a significant increase in BMI while awaiting surgery, postponing TKA may actually be detrimental.

Is Preoperative Weight Reduction in Patients Who Have Body Mass Index ≥ 40 Associated With Lower Complication Rates After Primary Total Hip Arthroplasty?

BACKGROUND

Given the heightened risk of postoperative complications associated with obesity, delaying total hip arthroplasty (THA) in patients who have a body mass index (BMI) > 40 to maximize preoperative weight loss has been advocated by professional societies and orthopaedic surgeons. While the benefits of this strategy are not well-understood, previous studies have suggested that a 5% reduction in weight or BMI may be associated with reduced complications after THA.

METHODS

We identified 613 patients who underwent primary THA in a single institution during a 7-year period and who had a BMI >40 recorded from 9 to 12 months prior to surgery. Subjects were stratified into 3 cohorts based on whether their baseline BMI decreased by >5% (147 patients, 24%), was unchanged ( ± 5%) (336 patients, 55%), or increased by >5% (130 patients, 21%) on the day of surgery. The frequency of 90-days Hip Society and Centers for Medicare & Medicaid Services complications was compared between these cohorts. There were significant baseline differences between the cohorts with respect to baseline American Society of Anesthesiologists class (P < .001) and hemoglobin A1C (P = .011), which were accounted for in a multivariate regression analysis.

RESULTS

In univariate analysis, there was a lower incidence of readmission (P = .025) and total complications (P = .005) in the increased BMI cohort. The overall complication rate was 18.4% in the decreased BMI cohort, 17.6% in the unchanged cohort, and 6.2% in the increased cohort. However, multivariable regression analysis controlling for potential confounders did not find that preoperative change in BMI was associated with differences in 90-days complications between cohorts (P > .05).

CONCLUSIONS

Patients who have a BMI >40 and achieved a clinically significant (>5%) BMI reduction prior to THA did not have a lower risk of 90-days complications or readmissions. Thus, delaying THA in these patients to encourage weight loss may result in restricting access to a beneficial surgery without an appreciable safety benefit.

Genetic polymorphisms of LMX1B and MLXIP are associated with hip osteoarthritis in the Chinese population

Aims: A large genome-wide analyses of UK Biobank data reported 15 novel loci associated with the susceptibility of hip osteoarthritis (HOA). We aimed to replicate the association of these loci with HOA in the Chinese population.Methods: A total of 13 Single Nucleotide Polymorphisms were genotyped in 892 HOA patients and 1123 healthy controls.Results: The risk allele frequency of rs62578127 and rs11059094 was significantly higher in the patients than in the controls. The mRNA expression of LMX1B (p = 0.01) and MLXIP (p = 0.001) were significantly increased in HOA tissues.Conclusion: We successfully replicated two novel susceptible loci of HOA and further characterized two potential causative genes.

Outcomes of Birmingham Hip Resurfacing Based on Clinical Aspects and Retrieval Analysis of Failed Prosthesis

This research aims to identify the prevalence of failure for Birmingham Hip Prosthesis (BHR) in total hip arthroplasty and to analyze its reasons from biomaterials and biofunctional perspectives. We present our current analysis and tests on a series of different BHR-retrieved prostheses after premature failure. Relevant clinical data, such as X-ray investigations and intraoperative images for clinical case studies, were analyzed to better understand all factors involved in BHR prosthesis failure. A detailed analysis of the failures highlighted uneven cement distribution, overloading in certain areas, and void formation in the material. A closer investigation using microscopical techniques revealed the presence of a crack originating from the gap between the cement mantle and human bone. Additionally, scanning electron microscopy analyses were conducted as part of the investigation to examine bone cement morphology in detail and better understand the interactions at the interfaces between implant, cement, and bone. In conclusion, this research emphasizes the importance of surgical technique planning and the cementation procedure in the success rate of BHR prostheses. It also underscores the need to carefully evaluate patient characteristics and bone quality to minimize the risk of BHR prosthesis failure. The cementation procedure seems to be essential for the long-term functionality of the BHR prosthesis.

Association between diabetes mellitus and total hip arthroplasty outcomes: an observational study using the US National Inpatient Sample

OBJECTIVES

To investigate the association of diabetes with postoperative outcomes in patients undergoing primary total hip arthroplasty (THA).

DESIGN

Retrospective cohort study using data from the US National Inpatient Sample (NIS).

SETTING

Study cohort was hospitalisations for primary THA in the USA, identified from the 2016-2020 NIS.

PARTICIPANTS

We identified 2 467 215 adults in the 2016-2020 NIS who underwent primary THA using International Classification of Diseases, 10th Revision codes. Primary THA hospitlizations were analysed as the overall group and also stratified by the underlying primary diagnosis for THA.

OUTCOME MEASURES

Outcome measures of interest were the length of hospital stay>the median, total hospital charges>the median, inpatient mortality, non-routine discharge, need for blood transfusion, prosthetic fracture, prosthetic dislocation and postprocedural infection, including periprosthetic joint infection, deep surgical site infection and postprocedural sepsis.

RESULTS

Among 2 467 215 patients who underwent primary THA, the mean age was 68.7 years, 58.3% were female, 85.7% were white, 61.7% had Medicare payer and 20.4% had a Deyo-Charlson index (adjusted to exclude diabetes mellitus) of 2 or higher. 416 850 (17%) patients had diabetes. In multivariable-adjusted logistic regression in the overall cohort, diabetes was associated with higher odds of a longer hospital stay (adjusted OR (aOR) 1.38; 95% CI 1.35 to 1.41), higher total charges (aOR 1.11; 95% CI 1.09 to 1.13), non-routine discharge (aOR 1.18; 95% CI 1.15 to 1.20), the need for blood transfusion (aOR 1.19; 95% CI 1.15 to 1.23), postprocedural infection (aOR 1.62; 95% CI 1.10 to 2.40) and periprosthetic joint infection (aOR 1.91; 95% CI 1.12 to 3.24). We noted a lack of some associations in the avascular necrosis and inflammatory arthritis cohorts (p>0.05).

CONCLUSION

Diabetes was associated with increased healthcare utilisation, blood transfusion and postprocedural infection risk following primary THA. Optimisation of diabetes with preoperative medical management and/or institution of specific postoperative pathways may improve these outcomes. Larger studies are needed in avascular necrosis and inflammatory arthritis cohorts undergoing primary THA.

Endophenotypes of Primary Osteoarthritis of the Hip Joint in the Bulgarian Population over 60 Years Old

Aim. To identify subgroups of patients with primary osteoarthritis of the hip joint (pHOA) with similar imaging and laboratory findings, disease evolution, and response to conventional therapies. Methods. We performed further statistical analyses on patient data from two published, double-blind, randomized, and placebo-controlled studies (DB-RCTs), which examined the effects of intra-articular corticosteroids (ia-CSs), hyaluronic acid (ia-HA)-KИ-109-3-0008/14.01.2014, and intravenous bisphosphonates (iv-BPs) -KИ- 109-3-0009/14.01.2014 compared to the country's standard pHOA therapy. The data span an 8-year follow-up of 700 patients with pHOA, including: 1. Clinical parameters (WOMAC-A, B, C, and T; PtGA). 2. Laboratory markers (serum calcium and phosphate levels; 25-OH-D and PTH, markers for bone sCTX-I and cartilage uCTX-II turnover). 3. Radiological indicators: X-ray stage (Kellgren-Lawrence (K/L) and model (Bombelli/OOARSI), width (mJSW), speed (JSN mm/year), and zone of maximum narrowing of the joint space (max-JSN)-determining the type of femoral head migration (FHM). 4. DXA indicators: bone geometry (HAL; NSA; and MNW); changes in regional and total bone mineral density (TH-BMD, LS-BMD, and TB-BMD). 5. Therapeutic responses (OARSI/MCII; mJSW; JSNmm/yearly) to different drug regimens (iv-BP -zoledronic acid (ZA/-5 mg/yearly for 3 years)); ia-CS 40 mg methylprednisolone acetate, twice every 6 months; and ia-HA with intermediate molecular weight (20 mg/2 mL × 3 weekly applications, two courses every 6 months) were compared to standard of care therapy (Standard of Care/SC/), namely D3-supplementation according to serum levels (20-120 ng/mL; target level of 60 ng/mL), simple analgesics (paracetamol, up to 2.0 g/24 h), and physical exercises. The abovementioned data were integrated into a non-supervised hierarchical agglomerative clustering analysis (NHACA) using Ward's linkage method and the squared Euclidean distance to identify different endophenotypes (EFs). Univariate and multivariate multinomial logistic regression analyses were performed to determine the impact of sex and FHM on clinical and radiographic regression of pHOA. Results. A baseline cluster analysis using incoming (M0) patient data identified three EFs: hypertrophic H-HOA, atrophic A-HOA, and intermediate I-HOA. These EFs had characteristics that were similar to those of patients grouped by radiographic stage and pattern ('H'-RPs, 'I'-RPs, and 'A'-RPs), p < 0.05). The repeated cluster analysis of M36 data identified four EF pHOAs: 1. Hypertrophic (slow progressors, the influence of the type of femoral head migration (FHM) outweighing the influence of sex on progression), progressing to planned total hip replacement (THR) within 5 (K/LIII) to 10 (K/LII) years. 2. Intermediate (sex is more important than the FHM type for progression) with two subgroups: 2#: male-associated (slow progressors), THR within 4 (K/LIII) to 8 years. (K/LII). 2* Female-associated (rapid progressors), THR within 3 (K/LIII) to 5 (K/LII) years. 3. Atrophic (rapid progressors; the influence of FHM type outweighs that of sex), THR within 2 (K/LIII) to 4 (K/LII) years. Each EF, in addition to the patient's individual progression rate, was also associated with a different response to the aforementioned therapies. Conclusions. Clinical endophenotyping provides guidance for a personalized approach in patients with pHOA, simultaneously assisting the creation of homogeneous patient groups necessary for conducting modern genetic and therapeutic scientific studies.