Friday, June 15, 2007 

Patients with lower back pain due to lumbosacral nerve root irritation often complain of knee pain.  The knee pain may occur with straightening the knee or with bending the knee.  

 We talked last week about the muscles that straighten the knee and today's topic will be on muscles that bend the knee (knee flexors) . However, if there is pain and spasm in muscles that straighten the knee (knee extensors), knee pain can occur with knee bending due to stretching the tight and shortened knee extensor muscles.  

To test the strength of the knee flexor muscles, the patient should be on his stomach and he bends the knee on the tested side. The examiner pushes down on the leg in order to straighten the knee.  

The knee flexor muscles are:

-          biceps femoris (L5, S1 nerve roots via the sciatic nerve)

-          semitendinosus (L5, S1 nerve roots via the sciatic nerve)

-          semimembranosus (L5, S1 nerve roots via the sciatic nerve) 

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Photograph showing the hamstring muscles (knee flexor) muscles supplied by the L5 and S1 nerve roots.  

Tags: hamstrings muscles, knee flexion, Lower back pain, lower body topics, nerve root irritation, sciatic nerve
Categories: Lower Body Topics