INJURY SPOTLIGHT: Obturator Internus Dysfunction
Do you have hip pain? Do you also have hamstring pain? Have you been told that you have Hamstring Tendonitis or 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 so, you may have obturator internus dysfunction.
The obturator internus (OI) is a hip muscle that originates deep within the pelvis, wraps out and inserts on the posterior aspect of the head of the femur (the thigh bone). The OI’s main function is to rotate the leg externally and has a major role in stabilizing the head of the femur into the hip socket.
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, a trigger point is involuntarily contracted muscle fibers within a whole muscle. Because the TrP is involuntarily contracted and we cannot voluntarily relax the muscle fibers, blood flow is reduced to that area of the muscle as well as surrounding nerves and other tissues. This loss of blood flow can then result in hypersensitivity directly at the site of the TrP as well as aching pain in the surrounding area. TrPs can be latent or active. A latent TrP is one that does not cause pain unless provoked, like with direct pressure, but it possesses the ability to cause unprovoked pain. An active TrP is one that refers pain to other areas without being provoked. OI trigger points can refer throughout the hip and leg on the side that it is originating from. This is a main reason why many patients are treated unsuccessfully for possible hamstring syndrome and/or gluteus medius dysfunction when really the root of their problem is deeper and located at the OI muscle.
IS IT 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 the OI muscle has many different referral patterns. Patients might say one day that they have pain on the lateral side 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.
Common OI Dysfunction Symptoms
The pudendal nerve runs in close proximity to the OI muscle which can become irritated with OI TrPs and can cause various other symptoms as well. Many patients come into Zion Physical Therapy for hip and leg pain with running and biking and the OI muscle is the culprit. However, the OI muscle is also highly involved with pelvic floor dysfunction due to the potential of the pudendal nerve involvement. The pudendal nerve branches into three smaller nerves which supply sensation and muscle control to the rectal, perineal and clitoral/penile areas. Because of these innervations, OI dysfunction and TrPs of the OI muscle can cause other symptoms such as urinary frequency, urinary burning, itching, tingling, shooting pains into the groin and abdomen and others.
OI pain can manifest itself in many different ways. If you have hip, low back or groin pain or abnormal pelvic floor symptoms that have not resolved with medical attention of any kind, then call Zion Physical Therapy to schedule an appointment and determine if OI dysfunction might be the cause of your pain.