Flexor Pollicis Longus

The flexor pollicis longus is a long thin muscle on the outer aspect of your forearm. It assists in moving your thumb.

Identifying the Flexor Pollicis Longus (Biel, 2005)



University of Washington Radiology


  • Origin: The flexor pollicus longus attaches at the anterior surface of the radius, the bone in your forearm that forms the bend of your elbow.
  • Insertion: The second attachment is at the distal phalange of the thumb, the bone that makes the top section of your tumb.
  • Action: This muscle flexes the interphalangeal joint of the thumb. This means that the muscle bends the joint between the joint between the top and bottom sections of your thumb. It also assists in in flexion of the metacarpophalangeal and carpometacarpal joints of the thumb, which are the joints that connect the base of your thumb to your hand, and the bones of your hand to your wrist. In other words, the flexor pollicis longus moves your thumb toward the palm of your hand.
  • Innervation: Flexor pollicis longus is innervated by the median nerve, which innervates your thumb, index, and middle fingers.


Causes of Tightness or Injury in Flexor Pollicis Longus (Pramod, 2017)

  • Prolonged gripping of objects (such as in a workshop)
  • Hand writing frequently
  • Spending a lot of time drawing or painting
  • Any activity that causes your thumb to be in flexion for prolonged periods


Symptoms of Tightness or Injury in Flexor Pollicis Longus (Pramod, 2017)

  • Pain or discomfort at joint or tip of the thumb
  • Difficulty grasping objects
  • Popping or locking of the thumb joint


Trigger Point Referral Pattern of Flexor Pollicis Longus (MyoRehab, 2014)



Image by the Abbott Center


  • Tip of the thumb
  • Palm of hand at the base of thumb


Relieving Pain in Flexor Pollicis Longus (Pramod, 2017)

  • Ice
  • Heat therapy
  • NSAIDs
  • Wrist stabilizer
  • Forearm compressor
  • Massage
  • Neuromuscular therapy




Flex – Bending a joint, decreasing the angle between the bones of the joint.

Insertion – The insertion of a muscle is the point at which the muscle attaches to a bone that is moved by that muscle. This point will be more distal (away from the core of the body) than the origin.

Origin – A muscle’s origin is the point at which the muscle attaches to a fixed, proximal (close to the core of the body) bone.

Trigger Point – An area of hyperactive tissue that sends excessive pain signals to the spine, which generally “confuses” the brain as to where the pain is coming from.


Please take note that none of the information in this article is meant to diagnose or treat any pathology. Please follow the advice of your primary care physician.



Biel, A., 2005. Trail Guide to the Body, Third Edition. Book of Discovery, Boulder, CO. Pp.161

“Flexor Pollicis Longus Trigger Point Diagram”. [Internet]. MyoRehab. [Updated 2014]. Available from: http://www.triggerpoints.net/muscle/flexor-pollicis-longus

Pramod, K. “Flexor Pollicis Longus Pain”. [Internet]. ePain Assist.  [Updated 1 Apr 2017]. Available from: https://www.epainassist.com/muscles-and-tendons/flexor-pollicis-longus-pain


About Tonya Sapiel, LMT

My goal with The Wellness Seeker blog is to educate the general public on the benefits of massage therapy, why it is an important addition to their health care routine, and what they can do to help themselves in between their massage therapy sessions. I welcome feedback and questions. I also accept requests for post topics. For more information about me or my practice, please visit www.tonyasapiel.massagetherapy.com

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