Background: In the last decade, regenerative therapies have become one of the leading disease modifying options for treatment of knee osteoarthritis (OA). Still, there is a lack of trials with a direct comparison of different biological treatments. Our aim was to directly compare clinical outcomes of knee injections of Bone Marrow Aspirate Concentrate (BMAC), Platelet-rich Plasma (PRP), or Hyaluronic acid (HA) in the OA treatment. Methods: Patients with knee pain and osteoarthritis KL grade II to IV were randomized to receive a BMAC, PRP, and HA injection in the knee. VAS, WOMAC, KOOS, and IKDC scores were used to establish baseline values at 1, 3, 6, 9, and 12 months. All side effects were reported. Results: A total of 175 patients with a knee osteoarthritis KL grade II-IV were randomized; 111 were treated with BMAC injection, 30 with HA injection, and 34 patients with PRP injection. There were no differences between these groups when considering KL grade, BMI, age, or gender. There were no serious side effects. The mean VAS scores after 3, 7, 14, and 21 days showed significant differences between groups with a drop of VAS in all groups but with a difference in the BMAC group in comparison to other groups (p < 0.001). There were high statistically significant differences between baseline scores and those after 12 months (p < 0.001) in WOMAC, KOOS, KOOS pain, and IKDC scores, and in addition, there were differences between these scores in the BMAC group in comparison with other groups, except for the PRP group in WOMAC and the partial IKDC score. There were no differences between the HA and PRP groups, although PRP showed a higher level of clinical improvement. Conclusions: Bone marrow aspirate concentrate, Leukocyte rich Platelet Rich Plasma, and Hyaluronic acid injections are safe therapeutic options for knee OA and provide positive clinical outcomes after 12 months in comparison with findings preceding the intervention. BMAC could be better in terms of clinical improvements in the treatment of knee OA than PRP and HA up to 12 months. PRP provides better outcomes than HA during the observation period, but these results are not statistically significant. More randomized controlled trials and high quality comparative studies are needed for direct correlative conclusions.

Knee arthroscopy is one of the most used operative treatments in orthopedic surgery. The first knee arthroscopy was performed by Prof. K. Takagi, from Tokyo, Japan, in 1920. With further improvement, he made the first black and white photos of the inside of the knee (1932) and, soon, the first color photos (1939). Independently from Takagi, Dr. Eugen Bircher from Arau, Switzerland, in 1921 published the results of 20 “arthro-endoscopies,” and that was the first time the word “arthroscopy” was mentioned in literature. In New York, USA, Dr. Michael Burman described in detail the incision points and technique of joint spreading that we use today. In 1957, Dr. Masaki Watanabe published the first Atlas of Arthroscopy. The first Arthroscopy Course in English language was held in Philadelphia, USA, in 1972. The International Arthroscopy Association, with Dr. Watanabe as president, was established in 1974. In clinical knee arthroscopy, the following division proved to be very useful: the medial compartment, the lateral compartment, the central part or central pivot, and the femoropatelar compartment. In this chapter, the normal anatomy of each of this part will be described in detail, with the descriptions of basic knee arthroscopy portals.

Discoid meniscus is an abnormality in which the cartilaginous meniscus is differently shaped, thick, and contains less collagen. It is mostly seen in children; and in the adult, it is rarely symptomatic. We have certain knowledge of discoid meniscus shape, its ultrastructure, epidemiology, and pathology. The discoid shape of the meniscus, which is seen mostly on the lateral meniscus, is described as an abnormality in which the cartilaginous meniscus, instead of the usual crescent type, is shaped like a full or partial disc, thickened, and covers more of the tibial lateral articular surface. The origin of the discoid shape is still not known. Some theories state that it is a normal finding during embryological development of the knee joint, some consider it as an atavism, and some consider it as a morphologic change during development. There are not many published studies on histological examinations. What is common is that the microstructure of the discoid meniscus differs in terms of the content and arrangement of collagen fibers. It is rarely symptomatic, so the true epidemiology of this abnormality is difficult to determine. In this chapter, we tried to make a cross-section of the current findings considering lateral discoid meniscus.