Several different specific tests can be applied to assess meniscal involvement. A positive result on any one test cannot by itself establish the presence of a meniscal lesion, but together with other objective findings, it can help in the differential diagnosis.

Diagnostic accuracy is improved by considering the results of three tests in combination. In general, all clinical tests tend to be less reliable in the presence of a concurrent ligamentous lesion and are less accurate in patients with degenerative lesions than in young patients with acute injuries [59]. Below are some tests that can be performed.

Anteroposterior (AP) and lateral knee radiography in young patients with acute trauma [64] may be combined with a Rosenberg projection [65] and a skyline view in subjects older than 40 years of age with suspected degenerative lesion. These imaging studies are required for detecting osteophytes or degenerative chondral changes through assessment of the joint space. They are also useful for detecting malalignment [66].

Magnetic resonance imaging (MRI) is the most powerful and accurate modality for the diagnosis of meniscal lesions. It provides additional information about the state of the ligaments and cartilage [67]. It depicts many of the essential features of meniscal tears needed for making treatment decisions: location, shape, length and depth [68, 69]. As for diagnostic accuracy, it has 86–96 % sensitivity in the detection of medial meniscus tears, with a specificity of 84–94 % [70, 71]. In reality, if a pathological signal is detected on one section only, the accuracy of the diagnosis of a medial meniscal tear is 55 %. The accuracy increases if the pathological signal is seen in at least two consecutive images [71]. MRI is also accurate in the detection of repairable meniscal lesions, and it has good sensitivity for determining irreparable lesions. One study has shown that 89 % (103 of 116) of meniscal lesions were classified equally at MRI and subsequent arthroscopy with regard to reparability. However, the same study demonstrated that MRI had variable accuracy in predicting the configuration of the meniscal lesion later identified with arthroscopy [72]. MRI diagnosis is, however, associated with a risk of false-negative or false-positive results. False-negative results are more common with lesions located in the outer half of the posterior horn of the medial meniscus or in the inner third of the meniscal body. These are small lesions detected clinically by palpation of the joint line; they are stable and may be treated conservatively [73]. False-positive results are more frequent and concern the posterior horn of the medial meniscus. They are caused by chondrocalcinosis in the meniscus or healed meniscal lesions, which often continue to show high signal intensity. In the presence of chondrocalcinosis, MRI sensitivity in the medial meniscus is 89 %, specificity is 72 % and accuracy is 81 %. One of the causes of the diagnostic difficulties lies in the differences in descriptive terminology and interpretation used by orthopaedic surgeons and radiologists with regard to the lesion being examined [74, 75].

In the past, meniscal lesions were treated with total meniscectomy. This occurred because the true functions of the meniscus were unknown, and in his 1940 paper “The Semilunar Cartilages”, McMurray wrote that “The cause of failure of meniscal removal lies in the failure to remove the entire affected cartilage” [79]. In 1948, Fairbanks published what is now a classical paper, in which he described the characteristic radiographic changes produced by meniscectomy. Whereas today it is clear that these changes reflect the disruption of the tibio-femoral joint due to loss of the meniscal protective function, Fairbanks observed that “It seems likely that narrowing of the joint space will predispose to degenerative changes, but a connection between these appearances and later osteoarthritis is not yet established and is too indefinite to justify clinical deductions” [50]. During most of the twentieth century, therefore, orthopaedic surgeons carried out a large number of total meniscectomies with good short-term outcomes [80]. However, looking at the results over longer follow-up periods, the negative outcomes became increasingly apparent. For example, Tapper and Hoover from the Mayo Clinic reported on the results of a retrospective study of 213 patients followed up from 10 to 30 years after their meniscectomy, in which only 68 % had good or excellent results and only 38 % were asymptomatic. Moreover, they found that those with a bucket-handle tear but with intact peripheral meniscal rim had higher rates of satisfaction [81].

In the light of these results, there is an increased awareness of the importance of meniscal function [82], and the current motto of orthopaedic surgeons is “Save the meniscus”. Recently, R. Verdonk stated that we have to “keep the meniscus… vestigial soft tissue structure in a self-maintaining transmission system” [83].

The development of arthroscopic techniques and related surgical instruments has facilitated the performance of partial meniscectomy, which has become a pillar of the treatment of symptomatic lesions. The short-term results of partial meniscectomies are very satisfactory. Jareguito et al. have reported that in 90 % of cases, they obtained good or satisfactory results at 2-year follow-up and that 85 % of these patients returned to the desired activity level. However, at 8-year follow-up, the results remained good or excellent in 62 % of cases, and only 48 % maintained the pre-injury level of activity [84]. All in all, the differences in the functional scores between total and partial meniscectomy decrease over longer follow-up periods, on average after 7–8 years. Lee et al., in a biomechanical study, demonstrated that also partial meniscectomy influences the transmission of articular loads. They concluded that the goal is to preserve the greatest amount of meniscus possible [85]. Thus, we have biomechanical and clinical evidence suggesting the superiority of partial meniscectomy, despite its limitations of not being able to maintain an adequate biomechanical behaviour and avoid degenerative changes.

Medial meniscectomy is performed with the patient under spinal anaesthesia or with local anaesthesia and sedation depending on the surgeon’s preference and anaesthesiological concerns. Generally, a tourniquet is applied to the upper thigh, although some surgeons prefer to carry out the arthroscopy without it. The limb may be placed in a leg holder or on a flat table with a lateral post: both devices allow a valgus force to be applied in order to correctly visualise the internal compartment. The classical arthroscopic access points are used (antero-medial and antero-lateral); the use of the supero-medial portal for the outflow cannula is optional. Using an arthroscopic probe, the lesion is carefully assessed: a flap, a radial lesion, a dislocated bucket handle, and degenerate appearance of a complex lesion are all indications for partial meniscectomy. In the case of a flap tear, the probe is used to accurately visualise the site of attachment to then go on to resect it and remove the free meniscal fragment. Bucket-handle tears can be treated with a variety of techniques. The one we prefer consists in first resecting the anterior attachment base and then, after having caught the meniscal fragment with an appropriate grasper through an accessory antero-lateral portal (just below the standard portal), resecting the posterior attachment from the medial portal while applying traction and torsion. If visualisation of the area of the posterior attachment base proves difficult, a varus force with the semiflexed knee can be applied to facilitate the passage of the instrumentation: this will help to open up the space between the medial femoral condyle and the posterior cruciate ligament. Finally, the contour is smoothed with a shaver. If the procedure involves the posterior horn of the medial meniscus, a valgus force with extended and internally rotated knee may be required. In all cases, before ending the procedure, the stability of the meniscal remnant needs to be assessed. In patients with excessively tight MCL, it may be justified to release it to ensure correct visualisation of the medial compartment: this can be done by performing multiple needle punctures subcutaneously.

Prompted by the studies of Arnozcky and Warren [5] on meniscal vascularity and healing potential, and also thanks to the introduction of new arthroscopic techniques, meniscal repair has become more widespread. The indications can be summarised as follows:

The contraindications are degenerate or poorly vascular meniscus tissue, patient’s age, patient’s limited compliance with the postoperative physiotherapy protocol, untreated knee instability, osteoarthritis, chronic lesions, longitudinal tears shorter than 1 cm, or radial tears. Several different techniques are available for meniscal repair:

The characteristics and location of the tear and the operator’s experience can influence the type of technique adopted, even though all-inside techniques are being increasingly used since they are relatively easy to apply and do not require accessory surgical accesses. However, several studies have raised the problem of the failure of these methods even though the results are all in all similar to those achieved with the inside-out technique. The possible complications of repair techniques for tears of the medial meniscus are: