Soft Tissue Injuries

• Injury to one of the hamstring muscles or to the tendon of the gastrocnemius or popliteus muscle can cause posterior knee pain. Other soft-tissue causes of pain are injury to the ligaments in the area or to the meniscus of the knee.
  
  

Blood Vessels

• If the popliteal artery becomes entrapped in the back of the knee, it can cause pain.
  
  

Nerves

• Nerve entrapment at the back of the knee can cause pain. Nerves that can become entrapped are the common peroneal nerve and the tibial nerve.
  
  

Cyst or Tumor

• Another reason for posterior knee pain is a Baker's (or popliteal) cyst, which is a swelling at the back of the knee usually caused by other knee problems. Tumors at the back of knee can also cause pain.
  
  

Other Causes

• Degenerative joint disease (osteoarthritis) can cause posterior knee pain. Other causes are postsurgical arthrofibrosis (formation of abnormal scar tissue after surgery) or bioabsorbable tacks (placed in the knee during surgery to help reattach soft tissues to the bone).