Compartment Syndrome

• If you are suffering from compartment syndrome of the posterior thigh, a muscle has become too big for the sheath that surrounds it. This results in pain and pressure. You are likely to feel cramps, weakness and a dull pain at the back of your thigh, according to Sportsinjuryclinic.net.
  
  

Sciatica

• Sciatica can cause pain in the back of your upper thigh. The pain can radiate down one or both of your legs and is the result of radiculopathy or acute nerve root compression. Depending on where the nerve has been pinched, the pain can radiate down the back of your leg to your foot or radiate to the front of your knee.
  
  

Pulled Hamstring

• If you have pulled a hamstring muscle, the pain that results will depend on the severity of the pull or strain. If you have a minor tear in your hamstring, you will feel tightness in the back of your thigh. Your leg may swell and you will be uncomfortable when you walk.
  
  

Intramuscular Contusion

• When there is an intramuscular tear or contusion, bleeding will occur but the fluid is unable to escape because the muscle sheath disallows this. This causes pain.
  
  

Intermuscular Contusion

• When an intermuscular tear occurs, the muscle and part of the sheath are both torn. This can result in upper back thigh pain. Fluids are able to escape, so healing from this injury will be quicker than from an intramuscular one.