• It is clear that the stiff total knee arthroplasty (TKA) is a multifactorial entity associated with preoperative, intraoperative and postoperative factors.

• Management of the stiff TKA is best achieved by preventing its occurrence using strategies to control preoperative factors, avoid intraoperative technical errors and perform aggressive, painless postoperative physical medicine and rehabilitation; adequate pain control is paramount in non-invasive management.

• Careful attention to surgical exposure, restoring gap balance, minimizing surgical trauma to the patellar ligament/extensor mechanism, appropriate implant selection, pain control and adequate physical medicine and rehabilitation (physiotherapy, Astym therapy) all serve to reduce its incidence.

• For established stiff TKA, there are multiple treatment options available including mobilization under anaesthesia (MUA), arthroscopic arthrolysis, revision TKA, and combined procedures.

Cite this article: EFORT Open Rev 2019;4:602-610. DOI: 10.1302/2058-5241.4.180105

• Some authors have reported that outpatient total knee arthroplasty (TKA) is a successful, safe and cost-effective treatment in the management of advanced osteoarthritis.

• The success obtained has been attributed to the coordination of the multidisciplinary team, standardized perioperative protocols, optimal hospital discharge planning and careful selection of patients.

• One study has demonstrated a higher risk of perioperative surgical and medical outcomes in outpatient TKA than inpatient TKA, including component failure, surgical site infection, knee stiffness and deep vein thrombosis.

• There remains a lack of universal criteria for patient selection. Outpatient TKA has thus far been performed in relatively young patients with few comorbidities.

• It is not yet clear whether outpatient TKA is worth considering, except in very exceptional cases (young patients without associated comorbidities).

• Outpatient TKA should not be generally recommended at the present time.

Cite this article: EFORT Open Rev 2020;5:172-179. DOI: 10.1302/2058-5241.5.180101

• Possible indications for a rotating hinge or pure hinge implant in primary total knee arthroplasty (TKA) include collateral ligament insufficiency, severe varus or valgus deformity (> 20°) with relevant soft-tissue release, relevant bone loss, including insertions of collateral ligaments, gross flexion-extension gap imbalance, ankylosis and hyperlaxity.

• The use of hinged implants in primary TKA should be limited to the aforementioned selected indications, especially for elderly patients.

• Potential indications for a rotating hinge or pure hinge implant in revision TKA include infection, aseptic loosening, instability and bone loss.

• Rotating hinge knee implants have a 10-year survivorship in the range of 51% to 92.5%.

• Complication rates of rotating hinge knee implants are in the range of 9.2% to 63%, with infection and aseptic loosening as the most common complications.

• Although the results reported in the literature are inconsistent, clinical results generally depend on the implant design, appropriate technical use and adequate indications.

• Considering that the revision of implants with long cemented stems can be challenging, in the future it would be better to use shorter stems in modular versions of hinged knee implants.

Cite this article: EFORT Open Rev 2019;4:121-132. DOI: 10.1302/2058-5241.4.180056

• The current applications of the virtual elements of artificial intelligence (AI), machine learning (ML), and deep learning (DL) in total knee arthroplasty (TKA) are diverse.

• ML can predict the length of stay (LOS) and costs before primary TKA, the risk of transfusion after primary TKA, postoperative dissatisfaction after TKA, the size of TKA components, and poorest outcomes. The prediction of distinct results with ML models applying specific data is already possible; nevertheless, the prediction of more complex results is still imprecise. Remote patient monitoring systems offer the ability to more completely assess the individuals experiencing TKA in terms of mobility and rehabilitation compliance.

• DL can accurately identify the presence of TKA, distinguish between specific arthroplasty designs, and identify and classify knee osteoarthritis as accurately as an orthopedic surgeon. DL allows for the detection of prosthetic loosening from radiographs.

• Regarding the architectures associated with DL, artificial neural networks (ANNs) and convolutional neural networks (CNNs), ANNs can predict LOS, inpatient charges, and discharge disposition prior to primary TKA and CNNs allow for differentiation between different implant types with near-perfect accuracy.

• Parkinson’s disease (PD) is a common neurodegenerative disorder.

• When patients with PD undergo total knee arthroplasty (TKA) for knee osteoarthritis, poorer knee function and poorer quality of life are obtained than in matched cohorts (MCs). However, the degree of patient satisfaction is usually high.

• The mean length of stay is 6.5% longer in patients with PD than in MCs.

• Compared with MCs, patients with PD undergoing TKA have a 44% higher risk of complications.

• In patients with PD, the overall complication rate is 26.3% compared with 10.5% in MCs; the periprosthetic joint infection rate is 6.5% in patients with PD vs 1.7% in MCs; and the periprosthetic fracture rate is 2.1% in patients with PD vs 1.7% in MCs.

• The 90-day readmission rate is 16.29% in patients with PD vs 12.66% in MCs. More flexion contractures occur in patients with PD.

• The rate of medical complications is 4.21% in patients with PD vs 1.24% in MCs, and the rate of implant-related complications is 5.09% in patients with PD vs 3.15% in MCs. At 5.3 years’ mean follow-up, the need for revision surgery is 23.6%.

• The 10-year implant survival, taking revision of any of the components as an endpoint, is 89.7% in patients with PD vs 98.3% in MCs.

• An age younger than 60 years, a body weight of 180 lb (82 kg) or more, performing heavy work, having chondrocalcinosis and having exposed bone in the patellofemoral (PF) joint are not contraindications for unicompartmental knee arthroplasty (UKA).

• Severe wear of the lateral facet of the PF joint with bone loss and grooving is a contraindication for UKA.

• Medial UKA should only be performed in cases of severe osteoarthritis (OA) as shown in pre-operative X-rays, with medial bone-on-bone contact and a medial/lateral ratio of < 20%.

• The post-operative results of UKA are generally good. Medium-term and long-term studies have reported acceptable results at 10 years, with implant survival greater than 95% for UKAs performed for medial OA or osteonecrosis and for lateral UKA, especially when fixed-bearing implants are used.

• When all implant-related re-operations are considered, the 10-year survival rate is 94%, and the 15-year survival rate is 91%.

• Aseptic loosening is the principal failure mechanism in the first few years in mobile-bearing implants, whereas OA progression causes most failures in later years in fixed-bearing implants.

• The overall complication rate and the comprehensive re-operation rate are comparable in both mobile bearings and fixed bearings.

• The survival likelihood of the all-polyethylene UKA implant is similar to that of metal-backed modular designs for UKA.

• Notable cost savings of approximately 50% can be achieved with an outpatient UKA surgery protocol. Outpatient surgery for UKA is efficacious and safe, with satisfactory clinical results thus far.

Cite this article: EFORT Open Rev 2018;3:363-373. DOI: 10.1302/2058-5241.3.170048

• Isolated posterior cruciate ligament (PCL) tears are much less frequent than anterior cruciate ligament (ACL) tears.

• Abrupt posterior tibial translation (such as dashboard impact), falls in hyperflexion and direct hyperextension trauma are the most frequent mechanisms of production.

• The anterolateral bundle represents two-thirds of PCL mass and is reconstructed in single-bundle techniques.

• The PCL has an intrinsic capability for healing. This is the reason why, nowadays, the majority of isolated PCL tears are managed non-operatively, with rehabilitation and bracing.

• Recent studies have focused on double-bundle reconstruction techniques, as they seem to restore knee kinematics.

• No significant clinical differences have been established between single versus double-bundle techniques, autograft versus allograft, transtibial tunnel versus tibial inlay techniques or remnant-preserving versus remnant-release techniques.

Cite this article: EFORT Open Rev 2017;2:89-96. DOI: 10.1302/2058-5241.2.160009

• The treatment of small to moderate size defects in revision total knee arthroplasty (rTKA) has yielded good results with various techniques (cement and screws, small metal augments, impaction bone grafting and modular stems). However, the treatment of severe defects remains problematic.

• Severe defects have typically been treated with large allograft and metaphyseal sleeves. The use of structural allograft has decreased in recent years due to increased long-term failure rates and the introduction of highly porous metal augments (cones and sleeves).

• A systematic review of level IV evidence studies on the outcomes of rTKA metaphyseal sleeves found a 4% rate of septic revision, and a rate of septic loosening of the sleeves of 0.35%. Aseptic re-revision was required in 3% of the cases. The rate of aseptic loosening of the sleeves was 0.7%, and the rate of intraoperative fracture was 3.1%. The mean follow-up was 3.7 years.

• Another systematic review of tantalum cones and sleeves found a reoperation rate of 9.7% and a 0.8% rate of aseptic loosening per sleeve. For cones, the reoperation rate was 18.7%, and the rate of aseptic loosening per cone was 1.7%.

• The reported survival of metal sleeves was 99.1% at three years, 98.7% at five years and 97.8% at 10 years. The reported survival free of cone revision for aseptic loosening was 100%, and survival free of any cone revision was 98%. Survival free of any revision or reoperation was 90% and 83%, respectively.

Cite this article: EFORT Open Rev 2021;6:1073-1086. DOI: 10.1302/2058-5241.6.210007

• The number of rotating-hinge total knee arthroplasties (RH-TKAs) is increasing. As a result, the number of complications related to these procedures will also increase.

• RH-TKAs have the theoretical advantage of reducing bone implant stresses and early aseptic loosening. However, these implants also have complication rates that cannot be ignored. If complications occur, the options for revision of these implants are limited.

• Dislocation of RH-TKAs is rare, with an incidence between 0.7% and 4.4%. If it occurs, this complication must be accurately diagnosed and treated quickly due to the high incidence of neurovascular complications.

• If the circulatory and neurological systems are not properly assessed or if treatment is delayed, limb ischemia, soft tissue death, and the need for amputation can occur.

• Dislocation of a RH-TKA is often a difficult problem to treat. A closed reduction should not be attempted, because it is unlikely to be satisfactory. In addition, in patients with dislocation of a RH-TKA, the possibility of component failure or breakage must be considered.

• Open reduction of the dislocation should be performed urgently, and provision should be made for revision (that is, the necessary instrumentation should be available) of the RH-TKA, if it proves necessary.

• The mobile part that allows rotation can have various shapes and lengths. This variance in design could explain why the reported outcomes vary and why there is a probability of tibiofemoral dislocation.

Cite this article: EFORT Open Rev 2021;6:107-112. DOI: 10.1302/2058-5241.6.200093

• Open reduction and internal fixation is the gold standard treatment for tibial plateau fractures. However, the procedure is not free of complications such as knee stiffness, acute infection, chronic infection (osteomyelitis), malunion, non-union, and post-traumatic osteoarthritis.

• The treatment options for knee stiffness are mobilisation under anaesthesia (MUA) when the duration is less than 3 months, arthroscopic release when the duration is between 3 and 6 months, and open release for refractory cases or cases lasting more than 6 months. Early arthroscopic release can be associated with MUA.

• Regarding treatment of acute infection, if the fracture has healed, the hardware can be removed, and lavage and debridement can be performed along with antibiotic therapy. If the fracture has not healed, the hardware is retained, and lavage, debridement, and antibiotic therapy are performed (sometimes more than once until the fracture heals). Fracture stability is important not only for healing but also for resolving the infection.

• In cases of osteomyelitis, treatment should be performed in stages: aggressive debridement of devitalised tissue and bone, antibiotic spacing and temporary external fixation until the infection is resolved (first stage), followed by definitive surgery with grafting or soft tissue coverage depending on the bone defect (second stage).

• Intra-articular or extra-articular osteotomy is a good option to correct malunion in young, active patients without significant joint damage. When malunion is associated with extensive joint involvement or the initial cartilage damage has resulted in knee osteoarthritis, the surgical option is total knee arthroplasty.