The sacroiliac (SI) joint connects the sacrum—the triangular bone at the base of the spine—to the ilium, the hip bone. These joints are strong and stable, with minimal natural movement. Their primary function is to transfer the weight of the upper body to the legs and act as shock absorbers during walking and standing. During pregnancy, hormonal and mechanical changes compromise this stability.
A hormone called relaxin softens the ligaments that stabilize the joints in the pelvis, allowing for the necessary widening in preparation for childbirth. This increased joint laxity can lead to instability and misalignment in the SI joint. The growing uterus and corresponding weight gain shift the body’s center of gravity forward. This combination places excessive strain on the SI joint, resulting in the deep, sharp, or aching pain commonly felt in the lower back and buttocks.
Postural and Daily Activity Adjustments
Small changes to daily movement patterns reduce strain on the SI joint. When sitting, keep both feet flat with knees parallel and avoid crossing legs, which places uneven pressure on the pelvis. Use a lumbar support pillow or rolled-up towel to maintain the lower back’s natural curve and distribute weight evenly.
When standing, distribute weight equally across both feet and avoid prolonged standing. For bending tasks, squat down using your legs and keep your back straight to minimize twisting forces on the pelvis. Single-leg weight-bearing actions, like dressing, should be performed while sitting down to prevent a painful joint shift.
Movements in and out of bed or a car should use the “log roll” technique, keeping the trunk and pelvis moving as one unit. To exit the bed, roll onto your side, keep knees pressed together, and push yourself up to a seated position, swinging both legs over the side simultaneously. Applying cold therapy (an ice pack) for 15 to 20 minutes helps reduce inflammation during sharp pain, while heat can be applied to relax stiff muscles.
Targeted Stretches and Gentle Strengthening
Strengthening the core and hip muscles provides a muscular “belt” of support to the pelvis, managing SI joint pain. Controlled movements are necessary, and any exercise that causes pain should be immediately stopped.
The pelvic tilt is a foundational exercise, performed lying on your back with bent knees or on all fours. Slowly tilt the pelvis by flattening the lower back curve and gently engaging the deep abdominal muscles. This rhythmic movement helps mobilize the joint and strengthen core stabilizers without excessive stress.
The Cat-Cow stretch, performed on hands and knees, releases tension in the lower back and sacrum through spinal flexion and extension. A gentle bridge exercise, where you lift the hips slightly while squeezing the glutes, strengthens the gluteal muscles often weakened during pregnancy.
To stabilize the pelvis during walking, side-lying clam shells target the hip abductor muscles. Lie on your side with hips stacked and knees bent, then slowly lift the top knee while keeping your feet together and hips stable. Perform these exercises slowly, focusing on muscle activation, and repeat for 8 to 12 repetitions daily. Consistency helps build the stability the ligaments can no longer fully provide.
External Support Devices
External support devices offer stability to the pelvis, working with strengthening exercises for relief. A sacroiliac (SI) belt is a narrow, non-elastic band worn low and snug around the hips, directly over the SI joints. It provides compression, stabilizing the joint and limiting movement caused by ligament laxity.
SI belts differ from full maternity belly bands, which primarily support the abdomen’s weight. The SI belt should be worn during activities that trigger pain, such as walking or standing. Avoid constant wear, as this can lead to over-reliance and muscle weakening.
Kinesiology tape (KT) is a flexible, elastic tape applied to the lower back and SI joints. KT reduces pain and improves function by providing proprioceptive feedback and gentle support. The tape is typically applied in an X-pattern or as two I-shaped strips. For sleeping, specialized pregnancy pillows placed between the knees and ankles ensure the hips and pelvis remain neutral and aligned.
Consulting Healthcare Professionals
While self-management techniques are effective, certain signs require professional medical consultation. Contact a healthcare provider if the pain limits your ability to walk or stand, or if you experience radiating pain that travels below the knee. Other warning signs include numbness, tingling, or weakness in the legs, or sudden, sharp pain accompanied by fever.
A physical therapist (PT) specializing in prenatal care can accurately diagnose the pain source and create a personalized treatment plan. They utilize manual therapy techniques, such as gentle joint mobilization, and provide guidance on the correct execution of targeted exercises. They also advise on the proper use of support devices and kinesiology tape application.
For medical pain management, acetaminophen (Tylenol) is the preferred over-the-counter option. It is safe for use during all trimesters when taken at the lowest effective dose for the shortest duration. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, should be avoided, especially after the 20th week of pregnancy, due to potential risks. In rare, persistent cases, a doctor may consider interventions like a localized steroid injection, but these are reserved for patients who have not responded to conservative therapies.