**5. Classification**

There were many classifications for medial meniscus root tear mostly based on anatomic classification. For the medial meniscus anterior root attachment according to Berlet et al. there were four patterns of insertion of the anterior root [36].

Type I has the insertion located in the flat intercondylar region of the tibial plateau.

Type II (most common) has more medial insertion, closer to articular tibial surface.

Type III has a more anterior insertion, which is on the downslope of tibia. Type IV shows no solid fixation.

For medial meniscus posterior root tear the most popular classification was classified by Laprade. The classification was based on the morphology of the tear and was classified into 5 types [37] (**Figure 6**).

Type I: partial stable root tear

Type II: complete radial tear within 9 mm from the bony root attachment. Type III: bucket-handle tear with complete root detachment.

Type IV: complex oblique or longitudinal tear with complete root detachment. Type V: bony avulsion fracture of the root attachment.

There was an arthroscopic classification by Bin et al. which developed a classification base on extrusion of the medial meniscus on MRI and finding of the torn site displacement. They were divided into 3 types; type A: non-displaced, type B: overlapped (the torn tissue overlap on each other), and type C: widely displaced [38] (**Figure 7**).

They found that the widely displaced group had a 4° greater varus deformity, and higher rates of meniscus extrusion, grade III or IV chondral wear in the medial femoral condyle and medial compartment osteoarthritis than did the nondisplaced or overlapped group.

Another classification by Kim et al. was made based on tear gap (**Figure 8**) of the medial meniscus posterior root in arthroscopic finding. The higher the tear type

#### **Figure 6.**

*Laprade's classification for medial meniscus root tear. Type I: Partial stable root tear. Type II: Complete radial tear within 9 mm from the bony root attachment. Type III: Bucket-handle tear with complete root detachment. Type IV: Complex oblique or longitudinal tear with complete root detachment. Type V: Bony avulsion fracture of the root attachment (redrawn from LaPrade et al. [37]).*

#### **Figure 7.**

*A–C: Bin classification base on arthroscopic finding of meniscal tear and gap. A: Non-displaced, B: Overlapped and C: Widely displaced.*

#### **Figure 9.**

*Classification of medial meniscus posterior root tear based on MRI by Choi et al. posterior medial meniscus root ligament was defined as from tibial attachment point of root ligament to just lateral from articular cartilage inflection point of medial tibial plateau. Ligament was subcategorized into three zones: (a) transition to posterior horn of medial meniscus at junction between root and posterior horn, (b) midsubstance within root ligament proper, and (c) entheseal at tibial attachment point of root ligament (redrawn from Choi et al. [24]).*

(increasing displacement of the tear gap in arthroscopic surgery), the higher association with degree of meniscal extrusion, chondral wear, and severity of arthritis. They were classified in to 5 types [39].

Type I: incomplete root tear. Type 2: complete root tear with no gap or overlapped; Type 3: complete root tear with gap measuring 1-3 mm. Type 4: complete root tear with gap measuring 4-6 mm. Type 5: complete root tear with gap measuring 7 mm.

There is an MRI classification based on the attachment of posterior medial meniscus root ligament. The term ligament is used because of the different of tissue component. This classification included both degenerative change and tear of the medial meniscus posterior root. They classified into 3 types; type a: Tear at transition to posterior horn of medial meniscus at junction between root and posterior horn, type b: Tear at midsubstance within root ligament proper, and type c: Tear at entheseal at tibial attachment point of root ligament [24] (**Figure 9**).

#### **6. Treatment**

According to the natural history of medial meniscus root tear, without proper treatment, there was a higher chance of progression of meniscal extrusion and osteoarthritis. Besides, the choice of treatment was still controversy because there were many factors which might lead to poor outcome. We divided the treatment into 2 categories: nonoperative and operative treatment.

#### **6.1 Nonoperative treatment**

The nonoperative treatment of medial meniscus posterior root tear was preserved for 1. Patients whose conditions were unfavorable for surgery. 2. Patients with advanced osteoarthritis of the knee (K-L grade III-IV) 3. Relieve pain before surgery. 4. Patients who could not follow the post-operative protocol. There were many methods of conservative treatment including taking non-steroidal antiinflammatory drugs, cortisone injections, use of unloader knee brace, physical therapy, gait aid (cane or crutch) use, and orthotic use. We recommend using gait aid and hinge knee brace to prevent further damage to the meniscus and reduced the pain in acute setting. However, the use of cortisone injection should be avoided in patients who were planned for surgical repair of the meniscus due to the risk of infection and possibility of interference with the healing of the meniscal tissue. Nonoperative treatment provided symptomatic relief but could not prevent the progression of osteoarthritis in long term follow up [7, 40]. The physical therapy could improve functional score and reduce the pain especially from degenerative meniscal root tear [41]. From the meta-analysis by Faucett et al., the 10 years progression of osteoarthritis was about 95% and 45% conversion rate to knee replacement surgery [42]. Conversion to total knee replacement were also higher in nonoperative treatment compare with meniscus root repair in other studies [7, 43].

#### **6.2 Operative treatment**

The treatment choices might depend on many factors. The goal of the operative treatment was to: 1. Relieve pain, 2. Increase quality of life, 3. Prevent progression of osteoarthritis and 4. Restore function of meniscus. Before proceeding to the operation, physicians needed to talk to their patients about the goal of treatment and consequence after surgery. For example, a patient suffering an acute tear of the medial meniscus root, but the patient could not follow the post-operative protocol due to economic problem. Then, meniscus repair might not be a good choice for this patient. The choices of operative treatment are list below.

#### *6.2.1 Meniscectomy*

Meniscectomy was the majority of procedures that were done for the meniscus in the past. The procedure included removing some part of the meniscal tissue which preserved most of the meniscal tissue called "partial meniscectomy", or totally removed all the meniscal tissue called "total meniscectomy". The goal of this operation was to relive symptomatic pain from the unstable meniscus. The mechanical irritation from the unstable meniscal tear could be removed. However, the meniscectomy in medial meniscal root tear was different from other meniscal tears. Because, in other meniscal tear such as radial tear or vertical tear, if most of the meniscal tissue could be preserved, the hoop stress function of the meniscus remained. On the other hand, no matter how much meniscal tissue was preserved in medial meniscus root tear, the function of the meniscus still impaired and articular cartilage would play a major role in weight bearing which could lead to articular damage later. Thus, meniscectomy should be done in low demand patients, patients with advanced osteoarthritis and mechanical symptom meniscal tear, patients with partial root tear and the remaining attachment were more than 50%, or patients with poor meniscal tissue quality. The procedure could relieve symptomatic pain and swelling in short term result but in long term results the knee joint could deteriorate. From a study by Krych et al., the conversion rate to total knee replacement at a mean follow up of 5 years was 54% [44]. The rate of total knee replacement was quite similar to other studies [7, 42, 45].

## *6.2.2 Meniscus root repair*

Meniscus root repair is getting more attention at present due to better long term outcome compared with non-repair treatment [46]. Meniscus root repair can restore the biomechanics of the knee joint. Hence, the distribution of the load was restored. Although the normal distribution load could not completely be restored due to the elongation of the suture after repair, the contact pressure and contact area could almost resemble an intact meniscus root knee [47, 48]. On the other hand, if non-anatomic repair was done, the distribution of the load might be abnormal. From a biomechanical study by Laprade in 2015, the mean and peak contact pressure were significantly increased after non-anatomic repair compared with normal and anatomic repair [49]. There were many techniques of repairing meniscus posterior root. All of them showed a significant improvement of functional outcome and reduced conversion rate to total knee replacement.

## *6.2.2.1 Transtibial pull out technique*

This technique was the most popular technique for repairing medial meniscus posterior root due to familiarity and ease of assessment to the instruments. Many companies provided specific instruments for the transtibial repair. The technical step involved the used drill from the tibia to the root attachment at the posterior tibia, stitched the tear meniscus, pulled the meniscus to the drill hole with a knot tied on the tibia (**Figure 10**). The disadvantages of this technique were: 1. Bungee effect on the repair site, 2. The risk of neurovascular injury due to the drill misplaced 3. Transtibial tunnel can interfere with concomitant procedures 4. possibility of suture elongation and abrasion through bone tunnel [50, 51].

Most of the clinical studies of transtibial pull out technique showed good functional outcome, prevent progression of osteoarthritis and reduced conversion rate of total knee replacement. The 10-year conversion rate was much lower compared with partial meniscectomy and nonoperative treatment (33.5% vs. 51.5% vs. 45.5%) [42]. In younger patients (<50 years) the risk of re-operation were higher than older patients. The activities and demands of younger patients might be more compared with older patients. As a result, the strength of fixation might not be enough in younger patients [52]. Although transtibial pull out repair prevented the progression of osteoarthritis, this could not completely prevent the

#### **Figure 10.**

*Schematic drawing showed transtibial pull out repair of the medial meniscus root. The long tibial tunnel along with the "bungee effect" have the possibility of suture abrasion and elongation.*

process. This helped only decelerate the process and most of the patients could not restore the meniscus extrusion [53, 54]. Healing of the repaired root and reduction of meniscal extrusion seem to be less predictable, being observed in two-third of the patients [55].

Stitches configuration might not play a major role for repairing the meniscal root. Modified Mason-Allen stitches had slightly better biomechanics in some studies but quite comparable to two simple stitches [56, 57]. There were no clinical different among repair configurations [58, 59].
