The Psoas muscle is a deep, angry hip flexor muscle in the front of the body. When tight, Psoas can cause a ton of tightness and pain in the body. Psoas muscle release could potentially be a key to ridding your body of pain, tightness, and finally unlocking those stiff hips.
Psoas Muscle Anatomy
The Psoas muscle (pictured above) is a hip flexor muscle that connects from the femur to the lumbar vertebrae. Psoas is one of 5 hip flexor muscles, and one of two that lies connects above the waistline (Iliacus is the other). The Psoas muscle runs right through your guts and can be difficult to access for deep tissue massage.
Psoas's connections at the femur and lumbar spine allow it to powerfully flex the hip, as in lifting the knee to the chest. A few moves that require work from the Psoas muscle are marching and walking up stairs. In addition, there is speculation that the Psoas muscle can take part in spinal stability by stiffening the lower back when the body lifts a heavy load.
The Psoas muscle gets notoriously tight from excess sitting. Simply during the nature of sitting, the hip flexor muscles shorten and wrench on the joints to which they are attached. In the case of Psoas tightness, pain can be referred to the lower back and front of the hip - read on to see what this looks like and why Psoas muscle release could be the key to relieving this tension.
Psoas Muscle Pain
Psoas muscle pain can be a particularly debilitating type of pain. When the Psoas muscle contains knots, trigger points, and extreme tightness, a predictable pain pattern tends to emerge as discovered by Travell & Simons work . This pain pattern can send pain screaming to the lower back and front of the hip - see the bright red areas in the image below.
Psoas Muscle Referred Pain Pattern 
Psoas Muscle Release
Now that we understand what the Psoas muscle is, what it does, and how it hurts - we can attack it with Psoas muscle release and potentially relieve a lot of pain. Psoas muscle release can be one of the single most liberating myofascial release techniques, due to the high amount of tension that can build up in the Psoas muscle. If you are a desk jockey or spend 8+ hours a day sitting - you will definitely want to read the rest of this post.
Psoas Release Tool
In order to successfully release the Psoas muscle, you are going to need the right tool for the job. *One note: Psoas muscle release can be done by the hands of a physical or massage therapist, but it can be very beneficial to have a tool on hand to release the Psoas muscle exactly when you need it - for instance after a long day slouching at work.
The most therapeutic, versatile Psoas muscle release tool is undoubtedly QL Claw. QL Claw was designed to release the 5 main muscles that can contribute to lower back pain when tight, and Psoas is high on that list. This is important because if you have a tight Psoas muscle, chances are high that you also have tension built up in other areas.
Read about Psoas muscle release and QL Claw below:
QL Claw - Muscle Release Tool
 Davies, Clair, and Amber Davies. The Trigger Point Therapy Workbook: Your Self-Treatment Guide for Pain Relief. 3rd ed., New Harbinger Publications, Inc., 2013.