Knee surgery has developed rapidly since 1960. In the late 70s the arthroscopy and instrumentations dedicated allowed minimally invasive techniques to achieve tissue sparing intra-articular ligament reconstructions that were once performed necessarily with ‘open’ techniques.

Avoiding surgical opening of the joints has reduced complications of interventions and timing of postoperative functional recovery.

Surgery of lesions of the menisci, traditionally performed only to remove the mechanical painful obstacle of the broken meniscus, has become in arthroscopy firstly selective removal of non-repairable meniscal lesions, later meniscal reinsertion in more favorable injuries, lately meniscal transplantation from donors (this field is still a controversial subject of studies and debates).

The lesions of the knee cartilage can also be treated in arthroscopy, with autologous osteocartilaginous pads taken during the same intervention in areas of joints not subjected to the load; alternatively, the system of cartilage cells (chondrocytes) cultivated ‘in vitro’ (taken in a previous first arthroscopy, and cultivated for a reasonable period of time).

Even dissected osteochondral (osteochondritis) parts of the femoral condyles, tibial articular and patellofemoral surfaces (see below) can be treated arthroscopically.

The pathology of patellofemoral space is solvable both with arthroscopic (medial alar suture and lateral alar release in young patients) and minimally invasive techniques (transposition of tibial tuberosity); when indicated the mini-open intervention of medial-forward transposition of the tibial tubercle technique according to Emslie-Maquet is quick and effective solution, with good cosmetic and excellent functional results; in hyper-pressure external syndrome of the patella (SHPE), the external arthroscopic alarotomy is a ‘gold standard’.

The anterior cruciate ligament is routinely reconstructed arthroscopically, mainly with the use of auto-transplantation (with central third of the patellar tendon or with semitendinosus and gracilis): the implant is put in place with synthetic absorbable or metallic pins and screws; another opportunity is utilizing tendons from donor (allograft), with the advantage of not subjecting the patient to the surgical tendon harvesting time, reducing post-operative pain and accelerating the recovery of function.

The posterior cruciate ligament, like the previous one, is reconstructed with arthroscopic technique, with similar opportunities and similar surgical functional results.

Also the fractures of the tibial plateau (internal and external), as well as of the femoral condyles, can be in many cases treated with ‘arthroscopy assisted’ technique: the reduction of the accesses, surgical accuracy of reduction and good and stable synthesis obtainable in arthroscopy (even with intraoperative fluoroscopic control) give excellent results.

The alterations of load axis of the knees is treated with minimally invasive technique and under fluoroscopic control, by means of selective corrective osteotomies of the tibia and of the femur (respectively in varus and valgus knee) with the aid of plates and screws ‘in addition’ or ‘subtraction’ that allow early joint mobilization.

Osteoarthritis of the knee is cured with the application of total or partial (unicompartimental) knee replacement, usually cemented, with ’tissue sparing’ surgical technique, for a comfortable post-op and early functional recovery; patellofemoral prosthesis are the most radical solution in cases of patellofemoral localized osteoarthritis.

The development of the surface prosthesis allows, in cases of deep but small articular lesions of femoral condyles or of tibial condyles, to restore proper joint mechanics without resecting too much bone, using implants of titanium and polyethylene of a minimum size with rapid and almost painless functional recovery.

The ‘gene theraphy’, also in the knee joint, is the most interesting future perspective for the restoration of the biological ideal mechanical conditions of the joints.