Do you have hip pain? Do you have hamstring pain? Have you been told that you have hamstring syndrome? When asked to describe where your pain is, do you feel like you need to point “up there” to really pinpoint the location of pain? If you answered yes to any of these questions, your obturator internus muscle could be contributing to the pain and dysfunction that you are experiencing.
The obturator internus (OI) is a hip muscle that originates deep within the pelvis, wraps out and inserts on the posterior aspect of the femur head (the top of the thigh bone when it combines to form the hip joint). The main movement function of the OI is to rotate the leg externally. In addition to external rotation, the OI plays a major role in stabilizing the hip joint and is an important pelvic floor muscle.
The picture on the right is depicting the OI in green and is being viewed from behind.
Muscle Dysfunction and Trigger Points
Just like any other muscle in the body, the OI can become dysfunctional and trigger points (TrP) can arise for various reasons. In general, TrPs are an involuntarily contracted group of muscle fibers within a whole muscle. Because the TrP is involuntarily contracted and we cannot consciously relax the muscle fibers, blood flow is restricted to that area of the muscle as well as surrounding nerves and other tissues. This decreased blood flow can then result in hypersensitivity directly at the site of the TrP as well as aching pain in and around the area.
TrPs can be latent or active. A latent TrP is one that does not cause pain unless provoked, like with direct pressure during a massage or foam rolling. An active TrP is one that is painful without provocation. A latent TrP has the ability to become active and therefore start causing unprovoked pain. Both latent and active TrPs have the ability to refer pain to other areas of the body based on the referral patterns of the muscle that the TrP is in. OI trigger points can refer throughout the hip and leg on the side that it is originating from and often refers pain into the posterior hip (glute region) and hamstring. This common referral pattern is a large reason why many patients do not have resolution of pain after treatment of a hamstring or glute syndrone diagnosis; their pain is manifesting in the posterior hip and/or hamstring but the origin of the pain and dysfunction is from the OI muscle.
Is it the OI?
Having had personal experience with OI Dysfunction and treating patients with the issue, I have found that there are a few initial cues that help to tease out whether a patient is suffering from OI dysfunction versus hamstring, piriformis and/or gluteus medius syndromes. The first major sign is that the patient has difficulty pinpointing one location of pain. This is because of the many different referral patterns that the OI muscle has. Patients might say one day that they have pain on the outside of their hip or the pain is in the buttock region. Then, on another day they might describe a burning-type of pain at the insertion of the hamstring muscle at the “sit bone”; or maybe all three at once. Upon further investigation of these muscles with deep palpation, the patients might report that there is soreness in the area but that is not their “familiar pain”.
The next appropriate question focuses on locating where the exact familiar pain is as best as possible. This can be achieved by ruling out other muscles first. When asking a patient to pinpoint the exact location of the majority of their pain I ask it three ways. First, I ask by pointing to a spot directly over the piriformis muscle. Second, I point to the origin of the hamstring muscle at the “sit bone” (red arrow). And thirdly, I ask is it “up there” (green arrow)? If with deep palpation just medially to the “sit bone” and above the bottom of the butt cheek, familiar pain is reproduced you could be suffering from OI Dysfunction.
OI Dysfunction Symptoms
The pudendal nerve runs in close proximity to the OI muscle. If there are latent or active TrPs in the OI, the pudendal nerve can get irritated and cause nerve symptoms such burning, pins and needles, shooting pain into the pelvic floor area or weakness of the pelvic floor muscles. The pudendal nerve is highly involved with pelvic floor functions such as helping to maintain urinary and fecal continence through innervating many of the pelvic floor muscles as well as providing sensation to the genitalia. Entrapment of the pudendal nerve is very rare and mostly seen in professional cyclists, however, irritation of the pudendal nerve can cause pelvic floor dysfunctions and the OI muscle could be playing a part in that irritation. Alleviating the irritation through manual work to the OI muscle, stretches and tailored exercises can significantly reduce symptoms and help prevent more permanent injuries that may occur with prolonged nerve irritation.
Many patients seek physical therapy to alleviate their hip and leg pain that they experience with running and biking but do not have full resolution. Evaluation and treatment of the pelvic floor, specifically the OI muscle, can significantly improve symptoms and help patients return to their sport pain and dysfunction free!
Carolyn Yates, PT, DPT is an athlete herself and is skilled in treating all musculoskeletal pains and disorders. She has taken extensive continuing education courses on how the function and mobility of the pelvic floor can effect your athletic abilities.