Sims’ position is a standard medical positioning in which a person lies on their left side with the left leg straight and the right hip and knee bent forward, creating a semi-prone posture that exposes the perineal and rectal areas for examination or treatment. Named after the nineteenth-century American gynecologist J. Marion Sims, it remains one of the most commonly used positions in clinical settings for procedures ranging from rectal exams to enema administration. The position is straightforward to achieve, generally well tolerated by patients, and carries a practical logic rooted in both anatomy and physiology that makes it distinct from alternatives like lithotomy or the knee-chest position.
How the Position Is Set Up
The classic Sims’ position places the patient on their left side on a flat surface such as a bed or examination table. The left hip and lower leg remain extended in a natural, straight line, while the right hip is flexed and the right knee is bent so that it rests on the surface or on a pillow for stability. The torso tilts slightly forward, somewhere between a true side-lying position and lying face-down. The arms rest comfortably alongside the body or in front rather than tucked underneath, which would restrict circulation and cause discomfort.
The bent right knee is a key detail. It prevents the patient from rolling fully onto their stomach, locks the pelvis at an angle that naturally separates the buttocks, and gives healthcare providers a clear line of sight and access to the rectal and perineal areas. That passive exposure is the whole point: the position does the work of opening up the relevant anatomy so that the clinician does not need to manually hold or reposition the patient during a procedure.
You will sometimes see the position referred to as the “left lateral position” or “left lateral recumbent position,” though these terms can also describe a fully side-lying posture without the semi-prone tilt. Sims’ position specifically involves that slight forward lean, which is what separates it from simple side-lying and makes it more useful for procedures requiring perineal access.
Where Sims’ Position Is Used in Practice
The position has a surprisingly wide range of clinical applications, though most of them share a common thread: they involve the lower gastrointestinal tract, the perineum, or the vaginal walls.
- Enema administration: The left-lateral orientation aligns with the natural anatomy of the sigmoid colon and descending colon, allowing fluid to flow with gravity rather than against it. This makes Sims’ position the default for most enema protocols.
- Rectal examination: The semi-prone tilt and flexed right knee expose the anal area comfortably, making digital rectal exams and proctoscopic evaluations easier to perform. Studies on proctologic examination positioning confirm that patients find Sims’ position comfortable and easy to get into on their own, saving the examining physician setup time.
- Postpartum perineal assessment: After vaginal delivery, clinicians often place the patient in Sims’ position to inspect the perineum for tears, swelling, or suture integrity. The natural exposure of the area makes it easier to evaluate without requiring the patient to assume a more physically demanding posture while recovering.
- Vaginal wall prolapse examination: The position allows gravity to act on the vaginal walls in a way that can reveal prolapse that might not be visible in other orientations. J. Marion Sims himself originally popularized the left lateral decubitus approach specifically for gynecological examination and treatment.
- Osteopathic manipulative treatment: Some manual therapy techniques use Sims’ position as a starting point for spinal and pelvic adjustments, particularly for the sacroiliac joint.
The position is also sometimes used for patients who are unconscious or recovering from anesthesia and need to be kept on their side to protect the airway. A modified lateral recovery position functions on the same principle, keeping the airway clear of secretions and reducing the risk of aspiration. Research comparing a modified recovery position to a conventional one during extubation after general anesthesia found that the modified approach reduced airway complications from about 18% to 6%.1PubMed. Frequency of Airway Complications with Modified Recovery Position versus Conventional Recovery position for Extubation after General Anaesthesia
How It Compares to Other Examination Positions
Sims’ position occupies a middle ground between several other standard clinical positions, and understanding those differences helps clarify why one might be chosen over another.
The lithotomy position has the patient lying on their back with both legs raised and supported in stirrups, knees bent and hips flexed. It is the default for most gynecological exams, Pap smears, and many surgeries involving the pelvic organs. Lithotomy provides the widest possible access to the perineum and vaginal canal, but it requires stirrups, is more physically demanding, and many patients find it more exposing. By contrast, Sims’ position can be set up on any flat surface with no equipment and gives the patient a degree of visual privacy because they are facing away from the clinician.
The knee-chest position has the patient kneeling face down with the chest against the surface and the buttocks elevated. It provides excellent exposure of the rectal area and is sometimes used for proctoscopy or certain rectal procedures. But it is physically uncomfortable, difficult for elderly or debilitated patients to maintain, and often perceived as undignified. Research on patient preferences for proctologic examination found that Sims’ position was better tolerated than knee-chest, particularly among older patients, and that most patients would favor it if given a choice.2PubMed Central. Patients’ views of medical positioning for proctologic examination
The prone position places the patient flat on their stomach. While it can be used for some spinal or posterior examinations, it does not naturally expose the perineal area the way Sims’ position does. The semi-prone tilt in Sims’ is what makes it more functional for rectal and perineal access than simply lying face-down.
For bedside nursing care, simple lateral (side-lying) positioning is used for turning patients to prevent pressure injuries. Sims’ position differs from generic side-lying by adding the forward pelvic tilt and the specific leg arrangement, which serve a procedural purpose rather than just a comfort or pressure-relief one.
Why Patients Tend to Prefer It
Comfort and dignity matter in clinical settings more than they sometimes get credit for, and Sims’ position performs well on both counts. In a study surveying patients about their experiences with various proctologic examination positions, the majority reported that no position was particularly embarrassing to them. But when asked which they would choose if given the option, most favored Sims’ position.2PubMed Central. Patients’ views of medical positioning for proctologic examination That preference held regardless of the patient’s sex, the age at which they first experienced an examination, or how recently they had been examined.
Part of the preference likely comes from how easy the position is to assume independently. A patient can roll onto their left side and bend their right knee without needing help, equipment, or instructions more complicated than “lie on your left side and pull your right knee up.” The knee-chest position, by comparison, requires the patient to get on all fours and lower their chest, which can be painful for anyone with joint problems, back issues, or limited mobility. For elderly or physically frail patients, Sims’ position is one of the most accessible options available.
The orientation also helps psychologically. Facing away from the clinician during a rectal or perineal exam can feel less exposing than the face-up, legs-apart arrangement of lithotomy. That small difference in perceived vulnerability can make a real difference in whether a patient is willing to return for follow-up care.
Physiological Reasons for Choosing the Left Side
The convention of lying on the left side specifically is not arbitrary. Two physiological factors support it.
First, the anatomy of the large intestine favors left-side positioning for procedures involving the rectum and sigmoid colon. The descending colon runs down the left side of the abdomen before curving into the sigmoid colon and then the rectum. Lying on the left side lets gravity assist in moving fluids like enema solution downward through this natural pathway rather than forcing them uphill.
Second, left-side lying appears to produce the lowest cardiovascular demand of any resting position. Research measuring heart rate, blood pressure, and oxygen consumption across multiple body positions found that left-side lying consistently produced the lowest values for all of these markers compared to right-side lying, supine, and sitting positions.3PubMed. Body position change and its effect on hemodynamic and metabolic status Blood oxygen saturation stayed stable across all positions, but the reduced cardiac workload in left-lateral positioning makes it a gentler choice for patients who are hemodynamically unstable or recovering from a procedure.
This hemodynamic advantage is also why left-side lying is recommended during pregnancy, particularly in the third trimester. The weight of the uterus can compress the inferior vena cava when a pregnant person lies on their back, reducing blood return to the heart. Left-side positioning shifts the uterus off the vena cava and improves circulation to both the parent and the fetus.
The Exaggerated Sims Position
A variation called the exaggerated Sims position takes the standard setup and amplifies the forward tilt and hip flexion. In this version, the upper hip and knee are flexed to 90 degrees or more, and the torso rolls further toward a prone orientation. The lower arm may be positioned either behind or in front of the trunk.4PubMed Central. Alternative Birthing Positions Compared to the Conventional Position in the Second Stage of Labor: A Review
This variant shows up most often in obstetric care during the second stage of labor. The exaggerated Sims position is considered a lateral birthing alternative to the conventional supine or semi-reclined positions. The idea is that the deeper forward tilt opens the pelvic outlet more effectively than the standard Sims arrangement, potentially improving the mechanics of the baby’s descent through the birth canal. It also takes pressure off the sacrum, which can be beneficial for women experiencing intense back labor.
The exaggerated version is not commonly used for the everyday clinical applications of standard Sims’ position. You are unlikely to encounter it during a routine rectal exam or enema. Its use is largely limited to labor and delivery settings and certain specialized manual therapy contexts.
Pressure Injury Considerations in Lateral Positioning
Any position that keeps a patient on one side for an extended period raises the question of pressure injuries, particularly in intensive care or surgical settings where patients may remain immobile for hours. The concern with lateral positions, including Sims’, centers on the bony prominences that bear weight: the greater trochanter of the hip, the lateral ankle, and the shoulder.
Clinical guidance on ICU positioning from the Italian Society of Anesthesia, Analgesia, Resuscitation and Intensive Care recommends managing trunk tilt angles carefully and using redistribution surfaces to mitigate pressure risk.5PubMed Central. The prevention of pressure injuries in the positioning and mobilization of patients in the ICU For short procedures like rectal exams or enemas, pressure injury risk is negligible. The concern becomes real when a patient is positioned laterally for extended periods in surgery, recovery, or critical care. In those contexts, padding between the knees, under the ankle, and beneath the shoulder becomes essential. A pillow between the legs to keep the hips aligned is standard practice for anyone spending more than a few minutes in a side-lying position.
For the typical clinical uses of Sims’ position, the duration of the procedure is usually short enough that pressure management is not a major concern. But nurses caring for immobile patients who are turned into a Sims-like position as part of a turning schedule should monitor those bony contact points and reposition at regular intervals.
When Sims’ Position Is Not the Right Choice
Despite its versatility, Sims’ position is not appropriate in every clinical scenario. Patients with significant hip or knee pathology on the right side may not be able to flex the upper leg comfortably, making the position impractical or painful. Shoulder problems on the left side can make lying on that side difficult. And patients with certain spinal conditions or recent abdominal surgery may not tolerate the semi-prone torso rotation well.
For procedures that require wide bilateral access to the pelvis or abdomen, lithotomy or supine positions are more practical. Sims’ position gives access primarily to the posterior and perineal areas, so anterior pelvic exams, abdominal palpation, and most surgical approaches to the lower abdomen call for the patient to be face-up.
In emergency situations where rapid airway management is needed, the standard recovery position (which is similar in concept but differs in arm and leg placement details) is typically preferred over the formal Sims’ arrangement, because recovery position protocols are more widely trained into first responders and prioritize airway protection over perineal exposure.
The Difficult History Behind the Name
J. Marion Sims is often called the “father of modern gynecology,” but that title carries a deeply uncomfortable history. Sims developed both the position that bears his name and the Sims vaginal speculum while performing experimental surgery on enslaved women in Alabama during the 1840s.6International Urogynecology Journal. The Sims position and the Sims vaginal speculum, re-examined He was attempting to repair vesicovaginal fistulas, a devastating childbirth injury that causes continuous urinary leakage, and he performed repeated painful surgeries on these women without anesthesia. One patient endured 29 failed operations over four years before Sims achieved a successful repair.
The ethics of this history have been debated with increasing urgency in recent years. Defenders have pointed out that anesthesia was not yet widely available or standardized during the period of Sims’ early experiments. Critics counter that Sims held beliefs, common among white physicians of the era, that Black patients did not experience pain in the same way as white patients, and that enslaved women could not meaningfully consent to experimental surgery. Statues of Sims in New York and elsewhere have been removed or relocated in response to public pressure.
The position and the speculum he invented remain in clinical use because they are genuinely useful tools. But knowing the history matters, both for understanding how medical progress has sometimes been built on exploitation and for recognizing why many patients and practitioners feel conflicted about the terminology. Some clinicians have quietly shifted to using descriptive terms like “left lateral position” in practice, though “Sims’ position” remains the standard name in textbooks and clinical guidelines.