Anatomy Of The Popliteal Fossa - Everything You Need To Know - Dr. Nabil Ebraheim

Dr. Ebraheim’s educational animated video describes the anatomy of the back of the knee - Popliteal Fossa.
The area of depression located at the back of the knee joint is called the popliteal fossa.
Bony anatomy
•Femur
•Tibia
•Fibula
Cruciate & collateral ligaments
•Posterior cruciate ligament
Muscle anatomy
•Popliteus m.
•Plantaris m
•Biceps m
•Semimembranosus m
•Soleus m
•Semitendinosus m
•Gastrocnemius m
Check the baker’s cyst bursa between the semimembranosus tendon medially and the medial head of the gastrocnemius laterally (cross section used in ultrasound)
Neurovascular bundle in the fossa
•Popliteal artery
•Popliteal vein
•Tibial nerve
•Common peroneal nerve
•The sciatic nerve travels down the thigh to the area of the popliteal fossa and at this point divides into the tibial and common peroneal nerves.
•The popliteal fossa is a closely packed—space. It is bounded by the biceps femoris laterally as well as the semitendinosus and semimembranosus medially. The lower part of the space is formed by the two heads of the gastrocnemius muscle.
Four common complications involving the popliteal fossa
1-Baker’s cyst: a baker’s cyst is a benign swelling found behind the knee that lies between the semimembranosus and the medial gastrocnemius muscles. A baker’s cyst is also known as the popliteal cust which lies posterior to the medial femoral condyle. The cysts is connected to the knee joint through a valvular opening. Knee effusion from intra-articular pathology allows the fluid to go through the valve to the cyst in one direction.
2-Popliteal artery entrapment syndrome: popliteal artery entrapment syndrome is a rare condition involving extrinsic compression of the popliteal artery behind the knee due to anomalous relationship of the muscle and artery in the popliteal fossa. It may also be caused by fibrous tissue constricting the artery. The condition usually affects young athletes who present with calf claudication. The blood flow will be decreased. The patient will complain of swelling, foot numbness and paresthesia, tingling of the toes and cramping of the muscles. Plantar flexion of the ankle and hyperextension of the knee will decrease the pulses. Arteriogram probably is the best study which will show the compression and the condition of the artery.
Treatment:
•Observation and activity modification
•Surgery may be needed to release the muscle to relieve the pressure on the artery
•Surgery may be done on the artery if it is affected.
3-Posterior knee dislocation occurs as a result of violent trauma. Most common mechanism of injury includes exaggerated hyperextension of the knee and dashboard injuries. The posteriorly directed force with the knee flexed to 90 degrees. Posterior knee dislocation may be associated with a high incidence of popliteal artery injury.
4-Posterior cruciate ligament injury: posterior translation of the tibia will occur with rupture of the posterior cruciate ligament. A common cause of this injury is a bent knee hitting a dashboard during a car accident, however it occurs more frequently in ports from forced hyperflexion of the knee.
PCL knee exam tests
•Tibial sag tests
•Quadriceps active test: the examiner stabilizes the leg of the patient and then the patient is asked to actively contract the quadriceps muscle. The tibia is seen being actively reduced from the posterior subluxed position.
•Lachman’s test: knee is bent 20-30 degrees. The examiner provides posterior force to the tibia while applying anterior pressure to the femur in order to access the posterior translation of the tibia.
•The posterior drawer test is carried out while the patient is in a supine position and the knee is flexed to 90 degrees. The amount of translation of the tibia relative to the femur is observed.
•The dial tests are performed while the patient is in the supine or prone position and both knees are in 90 degrees ( it shows the PCL injury) and 30 degrees of flexion (will show the posterolateral corner injury). More than 10 degrees external rotation indicated significant injury.

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