Popliteus tendinopathy is a knee injury which typically occurs in combination with other traumatic injuries of the lateral knee, especially posterolateral corner structures, posterior cruciate ligament (PCL), and meniscus 1. Less commonly, the tendinopathy may be secondary to non-traumatic causes, e.g. calcific tendinitis 2.
Traumatic popliteus injury has been described in both children and adults. Pediatric injuries tend to involve avulsion fractures of the popliteus tendon from the femur 3.
Given its typical injury mechanism, injury to the popliteus muscle may present with other symptoms of posterolateral corner injury, including:
- knee pain
- posterolateral knee instability
- failure of anterior cruciate ligament graft, if unrecognized with initial injury
The popliteus tendon is located at the deepest portion of the lateral knee and is intimately associated with other structures which comprise the posterolateral corner. The popliteus is often considered as a "popliteus complex", referring to its attachments: the popliteofibular ligament, popliteomeniscal fascicles (attaching to lateral meniscus), and its attachment to the posterior joint capsule 3.
As a component of the posterolateral corner, the popliteus functions to resist 3:
- varus stress (although less so than the lateral collateral ligament)
- external tibial rotation
- popliteus and popliteofibular ligament are major stabilizers during knee flexion, whereas lateral collateral ligament is a major stabilizer in knee extension
- posterior tibial translation
- isolated injury to the posterolateral corner results in only slight anterior or mild posterior instability
- injury to the posterolateral corner in combination with cruciate ligament injury results in more pronounced anterior or posterior instability
These forces also result in posterolateral corner injury. Importantly, the posterolateral corner structures also affect the load experienced by the cruciate ligaments of the knee 3.
Usually, there is no specific x-ray finding of popliteus tendinopathy. In calcific tendinitis, the popliteus may become calcified 2.
The popliteus is only visualized clearly on MRI. Findings which suggest injury include 1:
- focal tendon enlargement
- increased intratendinous or myotendinous signal on fluid-sensitive sequences
- complete tendon rupture or avulsion from the femur
Injury to the popliteus, especially in conjunction with injury to a lateral collateral ligament or posterolateral joint capsule, should raise suspicion for a posterolateral corner injury.
Treatment and prognosis
Management of posterolateral corner injuries is variable, but knee instability is generally considered an indication for surgical intervention. Co-injury of the lateral collateral ligament is often addressed simultaneously as a multi-ligament reconstruction 3.
In the event of popliteus tendon rupture and/or avulsion, both acute primary repair and delayed reconstruction of the popliteus have been advocated.
Primary repair techniques include the "recess procedure", which involves drilling a small tunnel at the site of osseous attachment and securing the ruptured tendon through the tunnel 3.
Reconstruction has been described using biceps femoris tenodesis, split tendon transfer, as well as a posterolateral corner "sling" procedure which makes use of an extra-articular tendon graft to provide structural reinforcement between the posterior tibia and the anterior lateral femoral epicondyle 3.
It is not uncommon to observe monosodium urate deposits around this tendon 4 if the popliteus tendon appears abnormal in the context of no trauma, consider gout.
- 1. Haaga JR, Boll DT. Chapter 63: Knee. In: CT and MRI of the Whole Body. (2016). 2176-2225. ISBN: 9780323113281
- 2. Adams SM., Hamming MG, Moorman CT. Chapter 102 - Lateral and Posterolateral Corner Injuries of the knee. In: Miller MD. Thompson SR. DeLee & Drez's Orthopaedic Sports Medicine (2015). 1195-1213. ISBN: 9781455743766
- 3. Doucet C, Gotra A, Reddy SMV, Boily M. Acute calcific tendinopathy of the popliteus tendon: a rare case diagnosed using a multimodality imaging approach and treated conservatively. (2017) Skeletal radiology. 46 (7): 1003-1006. doi:10.1007/s00256-017-2623-8 - Pubmed
- 4. Chou H, Chin TY, Peh WC. Dual-energy CT in gout - A review of current concepts and applications. (2017) Journal of medical radiation sciences. 64 (1): 41-51. doi:10.1002/jmrs.223 - Pubmed
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The knee is a complex synovial joint that can be affected by a range of pathologies:
- bone and cartilage
- distal femoral condyle fracture
- tibial plateau fracture (classification)
- patella fracture
avulsion fractures of the knee
- Segond fracture
- reverse Segond fracture
- anterior cruciate ligament avulsion fracture
- posterior cruciate ligament avulsion fracture
- arcuate complex avulsion fracture (arcuate sign)
- biceps femoris avulsion fracture
- iliotibial band avulsion fracture
- semimembranosus tendon avulsion fracture
- Stieda fracture (MCL avulsion fracture)
- patella fracture
- chronic avulsion injuries
- chondromalacia patellae
- osteoarthritis of the knee
- osteochondral defects
- osteochondritis dissecans of the knee
- pattern of bone contusion in knee injuries
- knee fractures
- anterior cruciate ligament tear
- anterior cruciate ligament ganglion cyst
- anterior cruciate ligament mucoid degeneration
- posterior cruciate ligament tear
- medial collateral ligament tear
- lateral collateral ligament tear
- medial patellofemoral ligament tear
- posterolateral corner injury
- posteromedial corner injury
- meniscal lesions
- meniscal tear
- meniscal/parameniscal cyst
- meniscal flounce
- meniscal fraying
- meniscocapsular separation
- bursosynovial lesions
- fat pad
- popliteal fossa