We have two serratus muscles the most common one that we all know serratus anterior muscle another less common one is serratus posterior muscle.
Serratus posterior muscle is intermediate layer of back muscles consists of serratus posterior superior and serratus posterior inferior.
Serratus posterior superior: C7-T3 vertebrae spinous process and Nuchal ligament.
Serratus posterior inferior: T11-L2 vertebrae spinous process
It inserts into ribs
Serratus posterior superior: at upper border of 2nd-5th ribs
Serratus posterior inferior: at lower border of 9th-12th ribs
Serratus posterior superior innervated by ventral rami of intercoastal nerves of T1-T5.
Serratus posterior inferior innervated by ventral rami of intercoastal nerves of T9-T12.
Serratus posterior superior: elevate the ribs during inspiration(accessory muscle of inspiration) and has a stabilization role for thorax.
Serratus posterior inferior: depress the ribs during expiration(accessory muscle of expiration)
Bilateral action of posterior superior/posterior inferior reduce extension of thoracic vertebrae.
Unilateral action: rotate spine to opposite side.
Serratus posterior superior and serratus posterior inferior especially serratus posterior superior may participate and cause myofascial pain syndrome and it's referred pattern can be overlapped with other muscles as it lies deeper.
This referred pain starts from back of shoulder runs to elbow and ulnar side of wrist, it may refer also to the chest and inner arm.
Serratus posterior inferior pain is localized and don't have referred pattern.
Another contribution to serratus posterior superior muscle is due to improper posture or inappropriate use of muscle for example holding phone between ear and shoulder that cause scapulocostal syndrome and may be misdiagnosed with the lesion of spinal nerves of cervical spine.
We can't palpate this muscle as it lies under trapezius, rhomboids, back muscles and others and to better exposure of SPS muscle we need to take shoulder blade out.
Patient can apply self message for SPS muscle using message ball or trigger fairy.
Message ball; place the ball beside your shoulder blade at the level of spine of scapula.
Then move your arm to the other side that will move your shoulder blade away and allow more exposure of muscle.
Once you find a trigger point stop and apply slow precise movement.
Trigger fairy; it's easier and less exhausting than message pall.
First, cross your arm to apposite side and use the contralateral hand to hold the trigger fairy place it on the muscle and search for trigger points,
When you find one stop and use the message fairy to apply circular movement or pull the fairy forward and downward.
For better results take slow deep breathing and elongate the exhalation while you stat on trigger point with fairy.
For referral pattern and self message and trigger point release for serratus posterior muscle www.muscle-joint-pain.com trigger point self treatment serratus posterior superior.
- Loukas M, Louis RG, Wartmann CT, Tubbs RS, Gupta AA, Apaydin N, Jordan R. An anatomic investigation of the serratus posterior superior and serratus posterior inferior muscles. Surgical and Radiologic Anatomy. 2008 Mar 1;30(2):119-23.
- Vilensky JA, Baltes M, Weikel L, Fortin JD, Fourie LJ. Serratus posterior muscles: anatomy, clinical relevance, and function. Clinical Anatomy: The Official Journal of the American Association of Clinical Anatomists and the British Association of Clinical Anatomists. 2001 Jul;14(4):237-41.
- Fourie LJ. The scapulocostal syndrome. South African Medical Journal. 1991;79(6):721-4.
- Richard Finn. Serratus Posterior Superior Richard Finn LMT, CMTPT, MCSTT. Available from: http://www.youtube.com/watch?v=HTbSxooHIRc[last accessed 12/3/2020]