Popliteus strain

Original Editors - Melissa Decoen as part of the Vrije Universiteit Brussel's Evidence-based Practice project

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Definition/Description

The popliteus muscle runs diagonally across the back of the knee joint. This muscle rotates the lower leg and plays a role in bending (flexing) the knee. The popliteus muscle helps to stabilize the back and outer back of the knee and is most often injured in downhill skiing and long-distance running. [1B] A M. Popliteus strain is a muscle strain.

Clinically Relevant Anatomy

The popliteus musculotendinous unit is unique in that the distal muscular attachment is designated the insertion and the tendinous proximal (femoral) attachment is designated the origin. The muscle inserts into a triangular area along the posteromedial aspect of the proximal tibial metaphysic above the soleal line. It forms the floor of the popliteus fossa. The tendon of the popliteus passes through the popliteal hiatus, entering the knee joint and inserting into the lateral femoral condyle at the end of the popliteal sulcus. The main tendinous component inserts into the lateral femoral condyle with variable aponeurotic attachments to the posterior horn of the lateral meniscus and the fibular head. [2A] The insertion into the lateral meniscus retracts and protects the meniscus in flexion, but this function has been disputed. The femoral insertion has a crescent shape, with the superior aspect being concave. [3B] The main tendon of the popliteus muscle consists of anterior and posterior fibers. [4B] The popliteus muscle is innervated by tibial nerves (L4-L5 and S1). [5B

Epidemiology /Etiology

The popliteus muscle functions as a dynamic internal rotator of the tibia. For this reason rupture of the popliteus muscle is usually associated with acute of chronic posterolateral instability of the knee. [4B] The isolated rupture of the popliteus tendon musculotendinous unit is an uncommon injury. [2A]
In some cases the injury is extensive and may include disruption of the arcuate ligament complex, the lateral collateral ligament, both cruciates, and the menisci. [6B,7B]

Characteristics/Clinical Presentation

Lesions have been reported occurring by a non contact external rotational mechanism: a sudden external rotation to a partially flexed knee [8A,9B,10B], a forced external rotation with a varus force application in some cases, or a forced external rotation with femur fixed [11B] have been described. Considering the type of tear, an overuse or degenerative mechanism could be considered as responsible of the partial tear. [4B]

Distinctive signs and symptoms:
• Pain over the outer side or back of the knee [1B]
• Painful resisted knee flexion or internal rotation [1B]
• Popliteal space tender [1B]

Differential Diagnosis

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Diagnostic Procedures

An acute haemarthrosis and lateral pain in a stable knee should lead to suspicion of an isolated injury to the popliteus muscle-tendon unit. [12B] The diagnosis should be entertained in any acutely swollen knee with posterolateral tenderness and pain on resisted internal tibial rotation. [8A]
MRI of the knee should be performed to evaluate the nature of the injury. The diagnosis may be confirmed by arthroscopic examination of the knee.
In some cases, the ruptured popliteus tendon retracts distally through the popliteal hiatus and can no longer be seen in the joint. [11B,14B,15B]

Outcome Measures

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Examination

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Medical Management

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Physical Therapy Management

The treatment of isolated popliteus tendon ruptures has not been very well defined. Review [8A](Method: MRI, Arthroscopy; Keywords: Popliteus tendon, rupture)of the literature shows 15 cases. [6B,7B,11B,12B,13A,14B,15B] Four were treated conservatively, in one case the avulsed chondral fragment was excised without repair of the popliteus tendon [11B]. In the remaining 10 cases, there was an osteochondral fracture as a result of avulsion of the tendon from the femoral attachment, and this fragment was reposited and fixed with screws.
In the other case, an attenuated intrasubstance tear was found in the tendon and this was repaired with non-absorbable sutures. The knee was then protected in a brace or cast for four to six weeks. It is noteworthy that in eight of these 10 cases, there was no instability on stress testing of the knee before the repair of the popliteus. In one case, the knee had minimal varus laxity at 30° of flexion, and in the last, there was subtle but clinically detectable posterolateral instability.[7B]
In all four cases treated conservatively , as well as in the case where the avulsed chondral fragment was excised without repair of the retracted popliteus tendon, good functional results were obtained. Long term follow up of these patients would further establish the efficacy of conservative treatment of popliteus musculotendinous unit injuries.[2A]

Key Research

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Resources

A.R.Guha, K.A. Gorgees, D.I. Walker: Popliteus tendon rupture: a case report and review of the literature. Br. J. Sports Med 2003; 37:358-360

Clinical Bottom Line

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Recent Related Research (from Pubmed)


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