Isolated popliteus tendon injury in a young patient: A case report

Abstract

Isolated popliteus injury is a rare clinical condition which can be treated either surgically or conservatively. Factors such as the patient's age, activity level, and cooperation with the medical team are determinants to choose the most optimal treatment option. A 29-year-old female patient presented with a knee injury caused by a low-speed motorcycle accident. Further examination suggested an isolated popliteus injury without any concomitant knee injury. We opted for surgical treatment, as it allowed us to act more confidently in the postoperative follow-up and the patient did not inspire confidence in the medical team in terms of close follow-up and compliance with the physical therapy protocols that would be required, if conservative treatment was chosen. In conclusion, isolated popliteus injury is a rare condition with no consensus on the treatment algorithm. Both surgical and conservative treatments can yield good to excellent results. Surgical treatment may be considered in selected cases where an optimal close follow-up regimen seems to be unlikely.

Introduction

An injury which only affects the popliteal tendon (PT) is a rare occurrence, as this tendon is part of the posterolateral corner (PLC) of the knee joint. The PT is one of three critical components of the PLC. If a PLC injury occurs, it is typical for other components of the PLC and/or the cruciate ligaments to also be injured.[1]

The PLC of the knee joint is composed of several structures, including the iliotibial band, biceps femoris muscle, popliteus muscle consisting of the popliteofibular ligament and popliteomeniscal fascicles, fabellofibular ligament, arcuate ligament, lateral gastrocnemius, and lateral collateral ligament.[2] The popliteal muscle, which consist of anterior and posterior fibers and originates from the posteromedial aspect of the proximal tibia, continues as an extra-articular but intracapsular structure. It passes through the popliteal hiatus and attaches to the lateral aspect of the femoral condyle. Although the isolated injury of this structure does not seem to cause instability, popliteus is the most significant part of PLC to prevent external rotation of tibia, and it is the primary internal rotator of tibia in non-weight-bearing status. It is a both static and active restraint for tibial external rotation. Popliteus functions both in closed and open chain phase of gait cycle and assists in knee flexion. It internally rotates the tibia in non-weight-bearing status. Popliteus referred as key to unlock the knee, that is due to the contraction of popliteus on weightbearing flexed knee, causing flexion and lateral rotation of the femur on the tibia.[1]

The incidence of isolated injuries to the PLC is relatively rare, and an isolated injury to the popliteus tendon is even rarer. Many orthopedic surgeons have a limited understanding of the complex anatomy and function of the PLC. The complexity and variability of the numerous structures in the PLC, as well as the limitations of imaging techniques, can make it difficult to fully comprehend this complex. This limited understanding of the anatomy and function of the PLC can lead to difficulty in diagnosing and treating such injuries.[2]

In this article, we present a female patient who had an isolated PT avulsion injury from its femoral insertion following a motorcycle accident and was successfully treated with surgery.

Case Report

A 29-year-old female patient was admitted to the emergency department after sustaining a knee injury in a motorcycle accident. During the accident, the patient fell from her motorcycle while accelerating slowly. She hit her flexed knee on the ground first and, then, her leg became trapped under the motorcycle. Following the accident, the patient experienced severe pain on the lateral side of her right knee and was unable to bear weight or walk.

Upon her physical examination, the patient's right knee was observed to be swollen with significant tenderness on the lateral femoral condyle. The range of motion (ROM) of her right knee was restricted by 10 degrees in both flexion and extension compared to her left knee. There was no varus-valgus instability in both extension and 30-degree flexion. During the Lachman test, a firm endpoint was observed with no detectable translation, while the anterior and posterior drawer tests were negative. Unfortunately, the pivot shift test could not be performed due to the patient's pain level. However, the dial test was conducted at both 30 and 90 degrees of flexion, suggesting that the patient's posterior cruciate ligament and PLC were intact.

Upon reviewing the radiographs, a cortical irregularity (Figure 1) was noted, leading us to suspect an avulsion injury. To confirm the diagnosis and rule out any potential bony injuries, a computed tomography (CT) scan was performed which revealed the presence of a bony fragment on the lateral side of the lateral femoral condyle (Figure 2). This fragment was found to be located at the site compatible with the popliteus femoral insertion. Subsequently, a magnetic resonance imaging (MRI) was performed, which confirmed our initial findings and indicated that the patient had sustained an isolated popliteus avulsion injury. Minimal effusion was observed in the joint (Figure 3), and other components of the PLC, cruciate ligaments, and medial structures were found to be intact. In addition, minimal degeneration of the posterior horn of the lateral meniscus was also noted on MRI.

Figure 1. Anteroposterior view of knee. Arrow depicting cortical irregularity on lateral femoral condyle.

Figure 2. Coronal slice of knee computed tomography. Arrow depicting popliteal avulsion from its femoral insertion.

Figure 3. Coronal slices of right knee magnetic resonance imaging. (a) Red arrow depicting popliteus avulsion injury, yellow arrows in (b) and (c) indicates lateral collateral ligament continuity.

The patient reported high clinical expectations and raised concerns about working in close collaboration with the medical team in case of non-operative treatment, which would require extended observation. Although both surgical and non-operative treatments have been reported in the literature with favorable outcomes, in this particular case, we decided to pursue the surgical option.

Under general anesthesia, a secondary examination was conducted, which confirmed the initial assessment and indicated no instability. The surgical procedure began with knee arthroscopy via the classic anterolateral and anteromedial portals. Cruciate ligaments were shown as intact and stable with probe, while the menisci appeared to be normal, except for a small incomplete horizontal rupture in the medial meniscus. An avulsed bony fragment was identified in the lateral gutter (Figure 4). An additional posterolateral portal was created to attempt reduction through arthroscopy, but it was unsuccessful. Therefore, we proceeded to the next step by enlarging the posterolateral incision. A straight 4-cm incision was made through the skin and subcutaneous tissue and, then, through the capsule. The bony fragment was reduced and fixed with a staple, and a knee immobilizer was applied.

Figure 4. Arthroscopic view of avulsed bony fragment.

Following the cessation of the motor block, open chain exercises, specifically straight leg raises, were initiated. The ROM exercises were introduced on the first postoperative day, as tolerated, using a continuous passive motion device. The patient was advised to wear the immobilizer at all times, except during ROM exercises. On the first postoperative day, the patient was able to ambulate with partial weightbearing using the knee immobilizer and two crutches. After reaching 90 degrees of active knee flexion, the patient was discharged on the third postoperative day.

During the sixth postoperative week, the knee immobilizer was removed, and full weight-bearing was allowed. The patient reported no symptoms and achieved full ROM. During follow-up, X-rays revealed initial indications of bony union of the avulsed fragment (Figure 5).

Figure 5. Six-week follow-up X-ray suggesting initial bony healing.

During the one-year follow-up, the patient complained of tenderness at the site where the staple was placed, but her knee examination was, otherwise, normal. An MRI was performed which revealed the integrity of the PT. To address the issue, a second surgery was performed, involving removal of the staple and a second look arthroscopy. The arthroscopy confirmed the integrity of both cruciate ligaments and menisci, while the PT was tested and found to be fully healed (Figure 6). After a further six months of follow-up, following the second surgery, the patient was free of symptoms and able to return to her pre-injury level of activity.

Figure 6. Arthroscopic view of healed popliteus tendon.

Discussion

Currently, there is no Level 1 evidence available on the treatment of isolated popliteus injuries in the literature. Reported cases of such injuries are summarized in Table I, suggesting no clear superiority of one treatment over another. Both surgical and conservative treatments have been reported with satisfactory outcomes. Various patient-related factors should be considered while deciding whether or not to opt for surgical intervention, with age being a prominent one. In skeletally immature patients, non-operative treatment may be the preferred option, since both treatment options are appropriate and there is an additional risk of epiphyseal damage in the surgical option. Wheeler et al.[8] published a case series of four patients who had good clinical results after conservative treatment, but the longest follow-up period in that study was only nine weeks. Liu et al.[15] reported two pediatric cases treated with suture anchors and achieved excellent results in the mid-term follow-up. On the other hand, advanced age may serve as a motivating factor for conservative treatment. While there is no established protocol for treating elderly patients, the fact that nearly all cases reported in the literature are of individuals under 30 years of age lends credence to this interpretation. In the case of our 29-year-old patient, she fell into a gray area in this regard and her age was not indictive for treatment of choice.

Table 1. Review of published cases of isolated popliteus injury

While considering the time required to return to sports, it is difficult to identify a clear standout method. To illustrate, Conroy et al.[10] reported a sixweek period before a professional soccer player could return to sports following arthroscopy. Quinlan et al.[6] also reported a professional rugby player with a rupture of PT at the musculotendinous junction who returned to their pre-injury level of participation after five weeks of rehabilitation. Algazwi et al.[7] reported a 16-year-old soccer player who returned to competitive sports after three months of conservative treatment. Early return to competitive sports was possible in both surgical and non-surgical groups, with most cases reporting a return after four to six weeks. Since there is no consensus in the literature on postoperative followup protocols and return to sport time, we applied the principles of our own knee surgery tradition. However, we acknowledge that we may have acted too cautiously on late full-weight-bearing, considering some authors have reported good results with early return to sport even after four weeks.

Most of the reported injuries occur during sports activities, and many of them lack a clear description of the trauma. Typical mechanism of injury is described as the rotation and anterior translation of the femur over the tibia in a flexed knee.[17] However, this was not the case in our patient, leading to the conclusion that not every patient presents with a classic description of the injury.[18] This may be a contributing factor to possible overlooked cases. Rotational or direct forces on a flexed knee seem to be the most inclusive description in reported cases. Localized tenderness on PLC and compatible radiological findings should raise flags about popliteus tendon injury.

It is worth noting that the cases reported in the literature mainly involve professional or semiprofessional athletes who have convenient access to personalized physiotherapy. This can lead to a potentially misleading interpretation of the favorable results reported with conservative treatment. The essential close monitoring and follow-up requirements for conservative treatment could not be optimally fulfilled given the patient's specific characteristics and our facilities. Consequently, we proceeded with surgical treatment which allowed us to implement more bold postoperative protocols for ROM and open chain exercises.

In conclusion, we opted for the surgical option based on the patient's characteristics in our case. It is of utmost importance to carefully assess the patient for any signs of instability or concomitant ligament injuries, as these may affect the treatment approach. Surgical treatment may be considered for patients who have higher expectations from medical professionals and may not be as compliant with mid- and long-term follow-up protocols. Access to appropriate physiotherapy should be also considered as a crucial factor in the decisionmaking process.

Citation: Vahabi A, Daştan AE, Kaya Biçer E, Aydoğdu S. Isolated popliteus tendon injury in a young patient: A case report. Jt Dis Relat Surg 2023;34(3):745-751. doi: 10.52312/jdrs.2023.1133.

Design, writing, data collection, literature review: A.V.; Design, literature review: A.E.D.; Idea, design, supervision, critical review: E.K.B.; Design, supervision: S.A.

The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

The authors received no financial support for the research and/or authorship of this article.

A written informed consent was obtained from patient.

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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