• Extensor mechanism failure in total knee arthroplasty (TKA) can present as quadriceps tendon rupture, patella fracture or patella tendon rupture.

• Component malrotation, excessive joint line elevation and previous lateral release are some of the risk factors contributing to extensor mechanism failure in TKA.

• Partial quadriceps tendon rupture and undisplaced patella fracture with intact extensor mechanism function can be treated conservatively.

• Extensor mechanism failure in TKA with disruption of the extensor mechanism function should be treated operatively as it is associated with poor function and extensor lag.

• It is recommended that acute repair of patella or quadriceps tendon rupture are augmented due to the high risk of re-rupture.

• Chronic ruptures of the extensor mechanism must be reconstructed as repair has a high failure rate. Reconstruction can be performed using autograft, allograft or synthetic graft.

Cite this article: EFORT Open Rev 2021;6:181-188. DOI: 10.1302/2058-5241.6.200119

• 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

• Osteoarthritis of the medial compartment, where the lateral compartment and patella-femoral joint are relatively spared, is a common orthopaedic presentation.

• Most frequently, the treatment of choice would be a total knee replacement, which involves removing healthy joint surfaces in such patients.

• Arthroscopic debridement in the osteoarthritic knee has fallen out of favour due to poor clinical results.

• A trend has developed towards less invasive surgery with uni-compartmental knee replacement (UKR) and high tibial osteotomy (HTO) gaining increasing popularity.

• Surgeons differ in their relative indications and contraindications to performing these procedures.

• Total knee replacement (TKR) continues to have the lowest overall revision rate of the available options.

• Growing evidence demonstrates more favourable patient-reported outcome measures in UKR and HTO patients, compared to TKR.

• Knee joint distraction (KJD) has been demonstrated as an alternative method of treatment in such patients.

Cite this article: EFORT Open Rev 2021;6:113-117. DOI: 10.1302/2058-5241.6.200102

• Over 100,000 total knee replacements (TKRs) are carried out in the UK annually, with cemented fixation accounting for approximately 95% of all primary TKRs. In Australia, 68.1% of all primary TKRs use cemented fixation, and only 10.9% use cementless fixation. However, there has been a renewed interest in cementless fixation as a result of improvements in implant design and manufacturing technology.

• This meta-analysis aimed to compare the outcomes of cemented and cementless fixation in primary TKR. Outcome measures included the revision rate and patient-reported functional scores.

• MEDLINE and EMBASE were searched from the earliest available date to November 2018 for randomized controlled trials of primary TKAs comparing cemented versus cementless fixation outcomes.

• Six studies met our inclusion criteria and were analysed. A total of 755 knees were included; 356 knees underwent cemented fixation, 399 underwent cementless fixation. They were followed up for an average of 8.4 years (range: 2.0 to 16.6).

• This study found no significant difference in revision rates and knee function in cemented versus cementless TKR at up to 16.6-year follow-up.

Cite this article: EFORT Open Rev 2020;5:793-798. DOI: 10.1302/2058-5241.5.200030

• Patellar resurfacing during total knee arthroplasty remains a controversial topic.

• Some surgeons routinely resurface the patella to avoid the increased rates of postoperative anterior knee pain and reoperation for secondary resurfacing, whilst others selectively resurface based on the presence of preoperative anterior knee pain, damaged articular cartilage, inflammatory arthritis, isolated patellofemoral arthritis, and patellar subluxation and/or maltracking. A third group of surgeons never resurface the patella.

• The anatomy and biomechanics of the patellofemoral joint as well as the advances in surgical techniques and prosthetic design must be taken into account when making a decision about whether to resurface the patella. Accurate component implantation if the patella is resurfaced becomes crucial to avoid complications.

• In our institution before 2008 we were performing a selective resurfacing of the patella, but in the last decade we have decided to always resurface it, with good outcomes and low complication rate. A reproducible surgical technique may be helpful in reducing the risk of postoperative anterior knee pain and complications related to implants.

• In this article we analyse the current trend and controversial topics in dealing with the patella in total knee arthroplasty, and discuss the available literature in order to sustain our choice.

Cite this article: EFORT Open Rev 2020;5:785-792. DOI: 10.1302/2058-5241.5.190075

• Total knee arthroplasty (TKA) is a satisfactory procedure for end-stage knee joint pathology. However, there is a significant incidence of unsatisfied patients.

• In recent years conventional total knee arthroplasty surgical technique has been challenged and a modern trend to respect individual anatomy, alignment and soft tissue laxities has been developed.

• The indications, limits and outcomes of these modern techniques in selected patients are not well-defined.

• Modern technology (navigation, patient-specific instrumentation and robotics) has improved accuracy of the osteotomies but their effect on long-term outcomes is still unclear.

• A technique which respects individual anatomy, laxities and alignment in combination with an implant which is designed to incorporate contemporary knee kinematics, without the use of modern technology, is presented.

Cite this article: EFORT Open Rev 2020;5:663-671. DOI: 10.1302/2058-5241.5.190085

• The menisci and articular cartilage of the knee have a close embryological, anatomical and functional relationship, which explains why often a pathology of one also affects the other.

• Traumatic meniscus tears should be repaired, when possible, to protect the articular cartilage.

• Traumatic articular cartilage lesions can be treated with success using biological treatment options such as microfracture or microdrilling, autologous chondrocyte transplantation (ACT), or osteochondral transplantation (OCT) depending on the depth and area of the lesion.

• Degenerative cartilage and meniscus lesions often occur together, and osteoarthritis is already present or impending. Most degenerative meniscus lesions should be treated first conservatively and, after failed conservative treatment, should undergo arthroscopic partial meniscus resection. Degenerative cartilage lesions should also be treated conservatively initially and then surgically; thereby treating the cartilage defect itself and also maintaining the axis of the leg if necessary.

• Tears of the meniscus roots are devastating injuries to the knee and should be repaired e.g. by transtibial re-fixation.

• The clinical role of ‘ramp’ lesions of the meniscus is still under investigation.

Cite this article: EFORT Open Rev 2020;5:652-662. DOI: 10.1302/2058-5241.5.200016

• Essential treatment methods for infected knee arthroplasty involve DAIR (debridement, antibiotics, and implant retention), and one and two-stage exchange arthroplasty.

• Aggressive debridement with the removal of all avascular tissues and foreign materials that contain biofilm is mandatory for all surgical treatment modalities.

• DAIR is a viable option with an acceptable success rate and can be used as a first surgical procedure for patients who have a well-fixed, functioning prosthesis without a sinus tract for acute-early or late-hematogenous acute infections with no more than four weeks (most favourable being < seven days) of symptoms. Surgeons must focus on the isolation of the causative organism with sensitivities to bactericidal treatment as using one-stage exchange.

• One-stage exchange is indicated when the patients have:

  1. minimal bone loss/soft tissue defect allowing primary wound closure,

  2. easy to treat micro-organisms,

  3. absence of systemic sepsis and

  4. absence of extensive comorbidities.

• There are no validated serum or synovial biomarkers to determine optimal timing of re-implantation for two-stage exchange.

• Antibiotic-free waiting intervals and joint aspiration before the second stage are no longer recommended. The decision to perform aspiration should be made based on the index of suspicion for persistent infection.

• Re-implantation can be performed when the treating medical team feels that the clinical signs of infection are under control and serological tests are trending downwards.

Cite this article: EFORT Open Rev 2020;5:672-683. DOI: 10.1302/2058-5241.5.190069

• Adverse knee pain occurs in 10–34% of all total knee replacements (TKR), and 20% of TKR patients experience more pain post-operatively than pre-operatively. Knee pain is amongst the top five reasons for knee replacement revision in the United Kingdom. The number of TKRs is predicted to continue increasing due to the ageing population.

• A narrative literature review was performed on the different causes of pain following TKR. A database search on Scopus, PubMed, and Google Scholar was conducted to look for articles related to TKR, pain, and cause. Articles were selected based on relevance, publication date, quality of research and validation. Relevant sections were added to the review.

• One hundred and fourteen articles were identified and potential causes of TKR pain included: arthrofibrosis, aseptic loosening, avascular necrosis, central sensitization, component malpositioning, infection, instability, nerve damage, overstuffing, patellar maltracking, polyethylene wear, psychological factors and unresurfaced patella.

• It is important to tailor our approach to address the individual causes of pain. Certain controllable risk factors can be managed pre-operatively to minimize post-operative pain. Risk factors help to predict adverse pain outcomes and identify specific causes.

• There are multiple causes of pain following TKR. Some factors will require further extensive studies, and as pain is a commonly attributed reason for TKR revision, its underlying aetiologies should be explored. Understanding these factors helps to develop effective methods for diagnosis, prevention and management of TKR pain, which help to improve patient outcomes.

Cite this article: EFORT Open Rev 2020;5:534-543. DOI: 10.1302/2058-5241.5.200031

• Although mechanical alignment (MA) has traditionally been considered the gold standard, the optimal alignment strategy for total knee arthroplasty (TKA) is still debated.

• Kinematic alignment (KA) aims to restore native alignment by respecting the three axes of rotation of the knee and thereby producing knee motion more akin to the native knee.

• Designer surgeon case series and case control studies have demonstrated excellent subjective and objective clinical outcomes as well as survivorship for KA TKA with up to 10 years follow up, but these results have not been reproduced in high-quality randomized clinical trials.

• Gait analyses have demonstrated differences in parameters such as knee adduction, extension and external rotation moments, the relevance of which needs further evaluation.

• Objective improvements in soft tissue balance using KA have not been shown to result in improvements in patient-reported outcomes measures.

• Technologies that permit accurate reproduction of implant positioning and objective measurement of soft tissue balance, such as robotic-assisted TKA and compartmental pressure sensors, may play an important role in improving our understanding of the optimum alignment strategy and implant position.

Cite this article: EFORT Open Rev 2020;5:486-497. DOI: 10.1302/2058-5241.5.190093