Objective: The purpose of this study was to describe the medial patellotibial ligament (MPTL) macroscopic anatomy and its histological analysis, in order to provide basis for future studies on its function, resistance and possible reconstruction.

Methods: MPTL morphologic details and histology were analyzed in 12 knees obtained from amputations. The ligament insertions and trajectory were described. Measurement of their length, width, tibial insertion center, and distance to the joint line and to the medial border of the patellar ligament were obtained with a digital caliper. A goniometer was used to measure the angle between the MPTL and the medial collateral ligament (MCL). The MPTL histological section was stained with hematoxylin and eosin and with the Masson trichrome staining protocol.

Results: The MPTL was present in all specimens. Its origin was at the medial patellar middle third. It followed a distal course, medial to the patellar ligament and inserted at the medial proximal tibia in a mean angle of 28.0 degrees relative to the MCL. Its mean length was 62.7 ± 8.4 mm. Its average width at the patellar and tibial insertions were 14.2 ± 2.4 mm and 11.1 ± 1.5 mm, respectively, and at the joint line, 8.7 ± 0.9 mm. The average distance from the MPTL tibial insertion center to the joint line was 21.2 ± 6.6 mm and from this center to the patellar ligament medial border, 15.6 ± 4.6 mm. The histological analysis showed that the studied structures had ligamentous characteristics.

Conclusion: The MPTL is an anatomic structure, which stretches consistently from the medial patellar middle third to the medial proximal tibia, made up of a dense regular connective tissue.

Patellar instability , Patellar ligaments , Anatomy , Histology

Gali JC, Junior CA, Nogueira F, Nakamichi Y, dos Santos NB, et al. (2017) Medial Patellotibial Ligament Anatomy and Histology. Ann Sports Med Res 4(3): 1111.

MCL: Medial Collateral Ligament; MPFL: Medial Patellofemoral Ligament; MPML: Medial Patellar Meniscal Ligament; MPTL: Medial Patellotibial Ligament

The patellar instability diagnosis, including femoropatellar subluxation and dislocation, is recurrent in orthopedics clinics. The yearly average risk of a primary dislocation within a segment of a randomly selected group is 31 to 100,000 cases, for individuals in the second decade of life [1]

The patellar stability depends on the accurate interaction among bone geometry, muscular action and passive restraints [2]. The medial soft structures are restraining to the lateral patellar dislocation. When the patella engages into the intercondylar notch, it is kept in place by the tension exerted by the medial soft tissues, and by the medial aspect of the lateral femoral condyle [3]. However, according to Yamada et al. [4], the patellar tilt in patients with recurrent patella dislocation, may be caused by individual differences in soft tissues balance, more often than because of intercondylar notch geometry.

The medial patellofemoral ligament (MPFL) is considered the main medial patellar static stabilizer [5-9]. Some authors believe that the medial patellotibial ligament (MPTL) is not functionally important [5,6,8]. Others consider that this ligament and the medial patellar meniscal ligament (MPML) together, have a secondary role in restraining lateral patellar dislocation [7]. Philippot et al. believe that the MPTL and the MPML are stabilizers mainly in flexion beyond 45° and, above all, in patellar rotation (accounting for 92% of the stabilization, at 90° of knee flexion) [9]; Marcacci et al. believe that the MPTL and MPML ligament complex have a relevant role in restraining the patellar lateral dislocation [10], and Ebied et al. understand that the absence of the MPTL may lead to the increase of translation and even lateral subluxation [11]

Surgical treatment may be required in cases of recurrent femoropatellar dislocation. Over the last years, there has been an increase interest of medial restraints reconstruction for the treatment of patellar instabilities, particularly the MPFL reconstruction, with good results [12]. According to Arendt et al., the establishment of a medial restraint by repairing or reconstructing the MPFL is a necessary component in all surgical procedures for the treatment of lateral instability of the patella [13]. According to Gobbi et al., the isolated MPFL reconstruction in patients with femoropatellar instability did not result in any improvement in the patellar tilt or shift, although no instability recurrence was detected among the operated patients. These authors believe that the MPFL reconstruction must be considered as a stabilization procedure instead of a proximal realignment surgery [14].

Conversely, there is little reference about surgical reconstruction of the MPTL in the literature. Some authors recommend their reconstruction combined with the MPFL [11,15-22] or vastus medialis obliquus advancement [20,21]. Others recommend only the isolated MPTL reconstruction [22]. Nevertheless, only the reconstruction proposed by Drez et al. nears an anatomical reconstruction, i.e. performed on the original ligament insertion area [15].

Surprisingly, there is little information about the MPTL anatomy. Some authors have written a brief description of its characteristics [5,6,23], whereas only Panagiotopoulos et al. [8] and Kaleka et al. [24] described its anatomy more thoroughly. However, the results of their research diverge in relation to the length, width, and the occurrence of MPTL, hence the need for further anatomical studies of this ligament.

The objective of this study was to describe in detail the macroscopic anatomy of the MPTL and to carry out histological studies of its sections in order to provide basis for its functions, biomechanics and surgical reconstruction future studies.

Our study was approved by the Ethics Committee of our institution. It was conducted in 12 knees obtained from abovethe-knee amputations performed for peripheral vascular disease. Patients’ ages at the time of amputation ranged from 43 to 93 (average of 62.9 years of age). Four individuals were male and eight were female. Seven of the knees were right knees and five were left.

Immediately following the amputation, the pieces were frozen and kept at a temperature below 15°C. The night prior to the dissection, the knees were removed from the freezer and left to thaw at room temperature. The skin and subcutaneous cellular tissue were removed, the fascia was opened, and the MPTL was dissected from its patellar origin to its tibial insertion.

The following morphological aspects of the MPTL were analyzed: location, measurements, in millimeters, of its insertions and at the joint line, its course, and respective measurements, also in millimeters, of its length, width, distance from the center of its tibial insertion up to the articular line, and from this center up to the medial border of the patellar ligament. Measurements were taken with a 150mm Pd150 digital caliper (Vonder®, OVD, Curitiba, Brazil).

The angle between the MPTL and the medial collateral ligament (MCL) was measured with a goniometer. Forward, the ligaments were removed and submitted to histological analysis with the Masson’s trichrome staining protocol and with hematoxylin and eosin.

All evaluations were done by two knee surgeons. The Wilcoxon nonparametric test was used to analyze whether the measurements were significantly different, i.e. whether the difference between them was considered null. This test was performed at a 95% confidence rate. Therefore, when the test p-value was less than 0.05, the hypothesis that the data had a zero average difference was discarded.

The MPTL was found in all knees studied. Its origin occurred at the medial patellar middle third. In all anatomical pieces studied the MPTL received fibers from the quadriceps tendon; in five knees (41.6%), it received fibers from the MPFL. Its average length was 62.7 ± 8.4 mm.

At the patellar origin its average width was 14.2 ± 2.4 mm. From here it followed a distal course, medial to the patellar ligament. At the level of the medial articular interline its mean width was 8.7 ± 0.9 mm. Its insertion occurred at the upper third of the proximal medial tibia, where its average width was 11.1 ± 1.5 mm.

The average distance from its tibial insertion center up to the medial articular line was 21.2 ± 6.6 mm, and from this center up to the medial border of the patellar ligament was 15.6 ± 4.6 mm. The distal segment of the MPTL formed an average angle of 28° with the MCL (Figure 1). In eight knees (66.6%) fibers from their tibial insertion interlaced with the hamstring tendons insertion.

The histological analysis showed that the ligaments studied presented a dense connective tissue, partly modeled, with collagen fibers parallels among them (Figures 2,3). All the results are expressed in Table (1).

The Wilcoxon test p-value was 0.141 (> 0.05). Therefore, the null hypothesis that difference of the results between the two evaluators was zero was not rejected, with a 95% confidence rate. Thus, we have considered that the measurements taken by both researchers were relatively the same.

The most important finding in our study was that the MPTL was present in all knees studied, as a thick structure, in layer II of the medial aspect of the anatomic pieces. Given their regularity, length and width we may conclude that this ligament has some relevant function. In fact, Philippot et al. [9] reported that the MPTL together with the MPML are the main stabilizers of patellar rotation, when the knee is flexed at 90°, and Ebied et al. reported that, with the absence of the MPTL, there may occur an increase of the knee rotation as well as lateral subluxation [11].

In the past, some authors regarded the MPTL as functionally irrelevant. However, research tests were performed with the knee at its full extension and 20° or less of external rotation [5], or flexed between 20° and 30° [6,8], flexion degrees where the MPTL has lower mechanical action [9]. Others, who have considered that the MPTL had a secondary role in restraining lateral patellar dislocation, studied the function with the knee flexed at 30° [7].

Figure 1 A : Illustration of the assessed anatomic structures. B: Picture of a desiccated piece depicting patellar insertion (B.1) and tibial insertion (B.2) of the MPTL and its location at the medial joint line (B.3), the angle (α) between the MPTL (medial patellotibial ligament) and the MCL (Medial Collateral Ligament) and the fibers stretching from the quadriceps (arrow).

*= the central point of its tibial insertion and,

**= medial limit of the patellar ligament

Figure 2: Histological section of the MPTL stained with the Masson trichrome staining protocol depicting parallel collagen fibers.

Figure 3: histological section of the MPTL, stained with hematoxylin and eosin, also depicting parallel collagen fibers.

On the other hand, few researchers referred to the MPTL as an important element for patellar stabilization [11,15-22]. Hinckel et al. [19] believe that the MPTL reconstruction may reduce the Q angle and improve the patellar excursion, without the medialization of tibial tuberosity, as it is known that the realignment of the tibial tuberosity, with the consequent change of orientation of the patellar ligament, may alter the pressure onto the femorotibial cartilage [25]. It has also been reported that small alterations in the femoropatellar alignment may cause significant changes of stress on the femoropatellar articulation and that mechanical changes in this articulation may cause changes in femorotibial compartments [2].

The knowledge of the MTPL anatomy is essential to enable reconstructive surgeries of this ligament. However, the literature related to this subject is still scarce.

For Conlan et al., the MPTL runs from the lower pole of the patella, oblique and inferiorly, up to the medial margin of the Hoffa’s fat pad, inserting at the anterior horn of the medial meniscus and the meniscotibial coronary ligament [5]. Desio et al. refer to the MPTL as an oblique condensation of fibers of layer I, which join the fibers of the MPTL at layer II, at the patella medial border, and which inserts at least 1 cm below the medial joint line [6] Arendt describes the MPTL as a condensation of the medial retinaculum, penetrating 1.5 cm below the articular line, near the MCL insertion [23].

Panagiotopoulos et al. studied the MPTL anatomy in eight knees of frozen cadavers immediately after their acquisition [8] and Kaleka et al. evaluated the secondary medial patellar restraints of 30 knees obtained from amputations, preserved in a 10% formaldehyde solution at 5.3°C [24]. The data comparison between these studies and ours can be found in Table (2).

Perhaps the main reason for the average length of the MPTL in our analysis being larger may be due to the origin of the ligament, which for us occurred at the patellar middle third as opposed to the distal third as in the other two studies. Panagiotopoulos et al. [8] considered the MPTL too thin, differently from our results and those of Kaleka et al. [24] These authors neither explained how the studies were performed nor did they indicate how many researchers took the measurements. On the other hand, the evaluation on the article written by Kaleka et al. was done by three different examiners and there is no mention to the interobserver agreement [24].

In our evaluations the MPTL received fibers from the quadriceps tendon in all knees studies, and in 41.6% of the specimens the MPTL obtained fibers from the MPFL. This blend of fibers from the MPTL, with others from the quadriceps tendon the MPFL, seems to create a ligament complex which may contribute to increase the femoropatellar stability. In 66.6% of the knees, fibers from their tibial insertion interlaced with the hamstring tendons insertion as if providing distal and medial anchorage.

No other publication in the medical literature refers to the proximal and distal integrations of the MPTL.

No research on Medline containing information about the 

Table 1 : Demographic data and results.

Table 2 : Comparison between Panagiotopoulos et al.8 , Kaleka et al.24 and our study

histological analysis of the MPTL. In our study, this ligament was made up of a dense regular connective tissue, partially modelled, with collagen fibers parallels among them, according to Chapman [26] should be histological characteristics of ligaments.

In our research, the MPTL was a constantly present element in all knees studies. Nevertheless, their individual role as restraints to the patella lateral dislocation is yet to be determined. Perhaps, better knowledge of its functions, associated with the anatomical fundaments we have described, may alter the surgical treatment of patellar instabilities in the future.

Our study have a few limitations. One of them is the small number of knees evaluated; the other is the relatively old age of patients when they underwent amputations, which could somehow contribute to alter the anatomy by degenerative processes intrinsic to biological aging.

The MPTL is an anatomic structure present in all knees evaluated, originating at the medial patella middle third, with a distal direction and inserting at the proximal and medial third of the tibia. It consists of a dense connective tissue, partially modelled, with collagen fibers parallels among them.

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