Popliteus Muscle

Original Editor - Hardik Bhatt

Description

Popliteus is the muscle of the leg.Its deepest muscle of the knee joint which forms the floor of the popliteus fossa. It is the only muscle in the posterior (back) compartment of the lower leg that acts just on the knee and not on the ankle.Its a thin, flat ,triangular shape muscle.

Origin

The lateral condyle of the femur and the posterior horn of the lateral meniscus, From there it runs inferiorly and mediolaterally towards the Tibia. Popliteus courses diagonally across the posterior upper tibia and a portion of the joint capsule to lie as the deepest muscle of the posterior knee region. Its tendon pierces the joint capsule but does not enter the synovium and is crossed by the arcuate ligament, the lateral collateral ligament and the tendon of biceps femoris. The popliteus bursa, which is usually an extension of the synovial membrane, separates it from the lateral femoral condyle. An additional head of popliteus may arise from a sesamoid in Gastrocnemius' lateral head and very rarely two other muscles may be present.

Insertion

It is inserted on the tibia just proximal to the soleal line but below the tibial condyles

Nerve

The popliteus muscle is supplied via fibres of the tibial nerve (L4-S1), direct through a section of the nerve towards the tibialis posterior muscle and also in some cases from a section via the main nerve towards the knee joint. These nerve fibres emerge through the fourth as well as fifth lumbar along with the first sacral spinal nerves to the popliteus muscle.

Artery

Muscular branches of Popliteal Artery supplies the popliteus muscle

Function

The popliteus muscle is an assistant knee flexor muscle

1. In open chain knee flexion movement, it rotates tibia medially
2. In close chain position knee movement it laterally rotates femur in the very beginning of knee flexion, as in close pack position knee is locked for stability by medial rotation of femur and popliteus laterally rotates the Femur in beginning of movement its called as 'key'of lock
3. It drags lateral meniscus posterior during knee flexion so prevents it from injury.
4. Knee stabilitiy,The popliteus tendon is frequently found to be connected to the lateral capsule. This gives the muscle a possible role in postero-lateral stability of the knee.Krudwig et al consider the Popliteus as an important structure resisting excessive external tibial rotation and maintaining the neutral tibial rotation, even if all other postero-lateral ligaments were cut.

Clinical relevance

Poor movement patterns and posture often weigh heavily on the popliteus muscle leaving it prone too weakness and injury. Any injury to the knee will likely involve the popliteus muscle.

If the hamstrings towards the outer thigh are stronger than the inner hamstrings, the popliteus muscle will be weaker. Excessive pronation or collapse of the inner foot when walking or running will stress the popliteus in the opposite direction.

Different EMG studied showed that popliteus muscle activitiy increases with knee extension and downhill walking so it is playing role to control hyperextension of knee. The reffered pain pattern in case of trigger point of popliteus muscle is back of knee.

More about popliteus muscle pathology on physiopedia Popliteus strain,Popliteus Tendinitis

Assessment

Due to deep location isolated injury to popliteus muscle is rare but it may be associated with other knee injuries such as ACL injury, meniscus injuries.

There are general symptoms of muscle injury like swelling, tenderness, odema, bleeding, patient keeps leg (tibia) in lateral rotation during knee flexion..

Following should be checked to rule out popliteus muscle injury.

1. Tenderness;-.As many neurovascular structure lie over it only terminal portions of popliteus muscle can be palpated.Tenderness over proximal popliteus tendon checked in prone lying position while tenderness over posterolateral knee may be sign of biceps femoris tendon strain and lateral meniscus injury.
2. Garrick test In high sitting position where hip and knee both flexed to 90 degrees resisted external rotation of lower leg is checked. Pain during manoeuvre considered as positive test
3. Shoe removal manoeuvrePatient tries to remove contralateral shoe by internally rotating affected leg to reach heel of another leg. Pain during manoeuvre indicates injury to popliteus muscle.

As said earlier isolated injury to popliteus muscle is rare ,nn isolated acute rupture of the popliteus tendon was found in 2 of 2412 knee MRI studies. 

The popliteus muscle along with PCL (posterior crucite ligament ) of knee stabilises femur over fixed tibia in stance phase specially when extra stabilitiy is needed like running downhill.So running downhill specially on banked surface and hyperpronation leads to popliteus muscle injury like tenosynivitis, tendinopathy, ruptute,strain.

Treatment

The treatment for popliteus muscle pathology same as per any soft tissue injury and muscle injury or tendinitis. RICE Therapy OR PRICE Therapy(protection,rest,elevation,compression,elevation ,and other anti-inflammatory drugs are given.

Physiotherapy treatment is on the line with other soft tissues and muscle injuries, mobility exercises, strengthening exercises, eccentric training and many more rehab protocols depending upon pathology, associated injuries and patients condition.