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• The optimal management of the patella during total knee arthroplasty (TKA) remains controversial and surgeons tend to approach the patella with one of three general mindsets: always resurface the patella, never resurface the patella, or selectively resurface the patella based on specific patient or patellar criteria.

• Studies comparing resurfacing and non-resurfacing of the patella during TKA have reported inconsistent and contradictory findings.

• When resurfacing the patella is chosen, there are a number of available patellar component designs, materials, and techniques for cutting and fixation.

• When patellar non-resurfacing is chosen, several alternatives are available, including patellar denervation, lateral retinacular release, and patelloplasty. Surgeons may choose to perform any of these alone, or together in some combination.

• Prospective randomized studies are needed to better understand which patellar management techniques contribute to superior postoperative outcomes. Until then, this remains a controversial topic, and options for patellar management will need to be weighed on an individual basis per patient.

Cite this article: EFORT Open Rev 2021;6:861-871. DOI: 10.1302/2058-5241.6.200156

• The Kinematic Alignment (KA) technique for total knee arthroplasty (TKA) is an alternative surgical technique aiming to resurface knee articular surfaces.

• The restricted KA (rKA) technique for TKA applies boundaries to the KA technique in order to avoid reproducing extreme constitutional limb/knee anatomies.

• The vast majority of TKA cases are straightforward and can be performed with KA in a standard (unrestricted) fashion.

• There are some specific situations where performing KA TKA may be more challenging (complex KA TKA cases) and surgical technique adaptations should be included.

• To secure good clinical outcomes, complex KA TKA cases must be preoperatively recognized, and planned accordingly.

• The proposed classification system describes six specific issues that must be considered when aiming for a KA TKA implantation.

• Specific recommendations for each situation type should improve the reliability of the prosthetic implantation to the benefit of the patient.

• The proposed classification system could contribute to the adoption of a common language within our orthopaedic community that would ease inter-surgeon communication and could benefit the teaching of the KA technique. This proposed classification system is not exhaustive and will certainly be improved over time.

Cite this article: EFORT Open Rev 2021;6:881-891. DOI: 10.1302/2058-5241.6.210042

• Unicompartmental knee arthroplasty (UKA) has several advantages over total knee arthroplasty; however, in many reports, the risk of revision remains higher after UKA.

• Many reasons for failure of UKA exist.

• Successful treatment starts with accurate assessment of the symptomatic UKA as a specific mode of failure requires a specific solution.

• A structured and comprehensive evaluation aids assessment of the symptomatic UKA.

• This review provides an overview of the causes for a symptomatic medial UKA, its risk factors, diagnostic modalities that can be used, and briefly discusses treatment options.

Cite this article: EFORT Open Rev 2021;6:850-860. DOI: 10.1302/2058-5241.6.200105

• Congenital femoral deficiency (CFD) is a rare disorder with several limb anomalies including limb shortening and knee cruciate ligament dysplasia.

• Limb lengthening is usually performed to correct lower limb discrepancy. However, complications, such as knee subluxation/dislocation, can occur during this treatment.

• Here, we explore CFD knee abnormalities and knee dislocation during limb elongation, discussing when and whether knee ligament reconstruction prior to the lengthening would be necessary to reduce the risk of knee dislocation.

• There is not enough support in the literature for the routine reconstruction of cruciate ligaments in CFD patients.

• Of note, in cases of severe anteroposterior or posterolateral rotatory instability, cruciate ligament reconstruction might be considered to decrease the risk of knee subluxation/dislocation during the lengthening treatment.

Cite this article: EFORT Open Rev 2021;6:565-571. DOI: 10.1302/2058-5241.6.200075

• Total knee arthroplasty (TKA) is an effective procedure to treat many patients with end-stage knee arthropathy. However, the extension of TKA for patients with Charcot neuroarthropathy (CNA) is controversial, with relatively limited evidence defining optimal reconstruction techniques.

• This systematic review of relevant studies that were published from January 2000 to June 2020 aimed to define survivorship, complications, reoperation, and component revision rates of contemporary TKA performed for CNA.

• We identified 127 TKA performed for CNA in five studies that comprised ≥ 7 knees with ≥ 5 years of follow-up.

• Overall implant survivorship was 85.4%. The overall complication rate was 26.4%, with the most common complications including instability (24.0%), periprosthetic fracture (17.4%), infection (13.0%), ligament injury (10.9%) and aseptic loosening (10.9%).

• The aetiology of CNA and prosthesis type had no influence on clinical outcomes, whereas the effect of staging of disease and ataxia status was still inconclusive.

• Understanding the potential determinants, survivorship and risk of complications related to TKA performed in CNA may help surgeons to deal with patient expectations.

Cite this article: EFORT Open Rev 2021;6:556-564. DOI: 10.1302/2058-5241.6.200103

• Knee osteoarthritis is a degenerative condition characterized by progressive cartilage degradation, subchondral damage, and bone remodelling. Among the approaches implemented to achieve symptomatic and functional improvements, injection treatments have gained increasing attention due to the possibility of intra-articular delivery with reduced side effects compared to systemic therapies.

• In addition to well-established treatment options such as hyaluronic acid (HA), cortico-steroids (CS) and oxygen-ozone therapy, many other promising products have been employed in the last decades such as polydeoxyribonucleotide (PDRN) and biologic agents such as platelet-rich plasma (PRP) and mesenchymal stem cells (MSCs). Moreover, ultrasound-guided intra-meniscal injection and X-ray-guided subchondral injection techniques have been introduced into clinical practice.

• Even when not supported by high evidence consensus, intra-articular CS and HA injections have gained precise indications for symptomatic relief and clinical improvement in OA. Biological products are strongly supported by in vitro evidence but there is still a lack of robust clinical evidence. PRP and MSCs seem to relieve OA symptoms through a regulation of the joint homeostasis, even if their capability to restore articular cartilage is still to be proved in vivo.

• Due to increasing interest in the subchondral bone pathology, subchondral injections have been developed with promising results in delaying joint replacement. Nevertheless, due to their recent development and the heterogeneity of the injected products (biologic agents or calcium phosphate), this approach still lacks strong enough evidence to be fully endorsed.

• Combined biological treatments, nano-molecular approaches, monoclonal antibodies and ‘personalized’ target therapies are currently under development or under investigation with the aim of expanding our armamentarium against knee OA.

Cite this article: EFORT Open Rev 2021;6:501-509. DOI: 10.1302/2058-5241.6.210026

• The full-length standing radiograph in an anteroposterior projection is the primary tool for defining and measuring limb alignment with definition of the physiological axes and mechanical and anatomic angles of the lower limb.

• We define the deformities of the lower limb and the importance of correct surgical planning and execution.

• For patients with torsional malalignment of the lower limb, computerized tomography scan evaluation is the gold standard for preoperative assessment.

Cite this article: EFORT Open Rev 2021;6:487-494. DOI: 10.1302/2058-5241.6.210015

• Revision total knee arthroplasty (rTKA) is a challenging procedure with often unreproducible results. A step-by-step approach is fundamental to achieving good outcomes.

• Successful surgery requires a correct diagnosis of the original cause of failure. Only with an accurate and detailed plan can surgeons overcome difficulties presented in this scenario.

• Any bone loss should be prevented during prosthetic component removal. Efficient tools must be chosen to avoid time-consuming manoeuvres.

• Joint reconstruction based on a ‘dual-zone’ fixation is essential to provide a long-term survivorship of the implant. The use of relatively short fully cemented stems combined with a biological metaphyseal fixation is highly recommended by authors.

• Flexion and extension gaps are accurately balanced after the establishment of the tibial platform.

• Varus-valgus laxity is commonly managed with a condylar constrained prosthesis. If hinged implants are required, a stronger implant fixation is needed to counteract constraints forces.

Cite this article: EFORT Open Rev 2021;6:495-500. DOI: 10.1302/2058-5241.6.210018

• Robotic-assisted total knee arthroplasty (RA-TKA) has shown improved reproducibility and precision in mechanical alignment restoration, with improvement in early functional outcomes and 90-day episode of care cost savings compared to conventional TKA in some studies. However, its value is still to be determined.

• Current studies of RA-TKA systems are limited by short-term follow-up and significant heterogeneity of the available systems.

• In today’s paradigm shift towards an increased emphasis on quality of care while curtailing costs, providing value-based care is the primary goal for healthcare systems and clinicians. As robotic technology continues to develop, longer-term studies evaluating implant survivorship and complications will determine whether the initial capital is offset by improved outcomes.

• Future studies will have to determine the value of RA-TKA based on longer-term survivorships, patient-reported outcome measures, functional outcomes, and patient satisfaction measures.

Cite this article: EFORT Open Rev 2021;6:252-269. DOI: 10.1302/2058-5241.6.200071

• Robotic total knee arthroplasty (TKA) has demonstrated improved component positioning and a reduction of alignment outliers with regard to pre-operative planning.

• Early robotic TKA technologies were mainly active systems associated with significant technical and surgical complications.

• Current robotic TKA systems are predominantly semi-active with additional haptic feedback which minimizes iatrogenic soft tissue injury compared to conventional arthroplasty and older systems.

• Semi-active systems demonstrate advantages in terms of early functional recovery and hospital discharge compared to conventional arthroplasty.

• Limitations with current robotic technology include high upfront costs, learning curves and lack of long-term outcomes.

• The short-term gains and greater technical reliability associated with current systems may justify the ongoing investment in robotic technology.

• Further long-term data are required to fully ascertain the cost-effectiveness of newer robotic systems.

Cite this article: EFORT Open Rev 2021;6:270-279. DOI: 10.1302/2058-5241.6.200052