• 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

• 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 main complications of surgical reconstruction of multiligament injuries of the knee joint are residual or recurrent instability, arthrofibrosis, popliteal artery injury, common peroneal nerve injury, compartment syndrome, fluid extravasation, symptomatic heterotopic ossification, wound problems and infection, deep venous thrombosis, and revision surgery.

• Careful surgical planning and execution of the primary surgical reconstruction of multiligament injuries of the knee joint can minimize the risk of the aforementioned complications.

• Careful postoperative follow-up is required to detect complications. Early recognition and prompt treatment are of paramount importance.

• To obtain good results in the revision surgery of failed multiligamentary knee reconstructions, it is crucial to perform a thorough and exhaustive evaluation to detect all the causes of failure.

• Addressing all associated injuries during revision surgery will lead to the best possible subjective and objective results, although functional outcomes are often modest.

• However, advanced age and high-energy injuries have been associated with the poorest functional outcomes after revision surgery of failed multiligament injuries of the knee joint.

Cite this article: EFORT Open Rev 2021;6:973-981. DOI: 10.1302/2058-5241.6.210057

• 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

• The complication rate of ankle arthroscopy (AA) ranges from 3.5% to 14%.

• To avoid such complications, it is essential to have a thorough understanding of the anatomy of the ankle, to perform the procedure very carefully and with appropriate instrumentation, and to use a non-invasive distraction technique.

• The most frequent complications are neurological (cutaneous nerve injuries), which are usually caused by direct injury during arthroscopic portals or by a distracting pin when using an invasive distraction technique. They usually resolve spontaneously within a few months.

• The iatrogenic formation of a pseudoaneurysm is a severe but extremely rare complication (an incidence of 0.008%).

• There are several treatments for pseudoaneurysms: external compression; direct thrombin injection, surgical intervention (resection of the damaged segment of the artery and reconstruction with a reversed long saphenous vein interposition graft), and endovascular embolisation.

• Other rare complications include wound infections (localised superficial infection), problems at the portal incisions (prolonged portal drainage, residual pain in the portal, portal scar dehiscence, cyst at the portal site), type I complex regional pain syndrome, instrument breakage, painful scars and nodules, and a number of other rarer complications.

• In conclusion, when performing AA, it is important to remember the potential complications and try to avoid them. When they do occur, it is essential to diagnose and treat them appropriately.