A 47-year-old construction worker fell in a street shaft and distorted his left knee. Knee MRI revealed a posterior cruciate ligament tear and an injury of the posterolateral complex. Primary therapy remained conservative.
A 47 year old construction worker fell in a street shaft and distorted his left knee. He presented with severe pain, a reduced mobility (extension - flexion 0 - 0- 90°) and a slight joint effusion. X-ray and multislice- CT excluded a fracture. Because of continuing pain and increasing joint effusion MRI of the knee was performed (Siemens Harmony 1.0 T, Knee coil, T1SE cor, Tirm cor, T2TSE tra, T2*medic sag 4 mm slices and T2TSE sag angled for the cruciate ligaments 3 mm slices).
Besides a rupture of the posterior cruciate ligament (Figure 1), a tear of the myotendinous junction of the popliteus muscle was diagnosed (Figure 2, 3) and an extensive edema of its muscle belly was visible (Figure 4, 5). The attachment to the lateral femoral sulcus was intact (Figure 6). Motoricity and sensibility of the leg were not impaired. A posterolateral instability was not stated by physical examination. Primary therapy remained conservative.
The popliteus muscle is an important structure for posterolateral stabilization of the knee and arises from the lateral femoral condyle and attaches at the posterolateral margin of the proximal tibia. Its tendon attaches to the posterior horn of the lateral meniscus and the fibular head. Beside its function as a stabilizer the muscle is the initiator of internal rotation in a "non weight bearing state" [1].
Injuries of the posterolateral complex (consisting of popliteus, ligamentum arcuatum, lateral collateral ligament et al.) are less common than medial or anterolateral knee injuries and are usually combined with cruciate ligament ruptures. LaPrade et al. reported an incidence for posterolat knee tears of 9.1% among all acute knee injuries with hemathrosis (331 patients) [2]. Mechanisms for these traumas are untypical and consist of „sudden external rotation of the tibia with a partial flexed weight-bearing knee“ [3]. MRI has been described as reliable method for detection of lesions of this complex [1]. Lesions of muscle belly and tendon lesions of popliteus can be easily differentiated on MRI [4].
Isolated lesions of the politeus muscle are rare findings. A complete rupture of popliteus leads to a posterolateral instability of the knee while minor lesions induce pain and reduce smoothness [5].
Treatment of minor lesions without instability has been recommended as conservative. Surgery is beneficial for major lesions when origin and/ or advance of the popliteus muscle are dislocated [6]. Guha AR et al. gave a review of the literature in 2003 concerning surgical and conservative management of popliteus tendon tears. Based on the given data they concluded that if a knee is stable though a politeus tear is obvious surgery may not be superior to conservative treatment and proposed a clinical long term follow up to prove efficacy of conservative treatment [5].
Myotendinous tear popliteus muscle with extensive edema.
Based on the MRI images of this patient (47 years old, male, left knee injury):
Based on the imaging findings and clinical history, the primary considerations include:
The above diagnoses may coexist or occur in parallel and require correlation with clinical examination (e.g., external rotation stress test, posterior drawer test) and patient history for comprehensive assessment.
Considering the patient’s age, history of trauma (fall with a twist injury to the left knee), and MRI findings, the most likely diagnosis is:
Popliteus tendon and muscle belly injury (partial popliteus tear) combined with posterior cruciate ligament (PCL) tear and mild posterolateral corner damage.
If further confirmation of popliteus tendon tear or the extent of ligament tear is needed, stress MRI of the knee or arthroscopic evaluation may be considered.
Rehabilitation should be carried out step by step according to the severity of injury and individual circumstances, following FITT-VP principles:
Throughout rehabilitation, closely monitor for pain, swelling, or instability. Reduce training load and seek follow-up evaluations if necessary to ensure safety and effectiveness.
Disclaimer: This report is a reference-based analysis using currently available imaging and patient history. It does not substitute for an in-person consultation or professional medical advice. Specific diagnosis and treatment still require clinical assessment and further investigations.
Myotendinous tear popliteus muscle with extensive edema.
