Indents in the back are a relatively common anatomical feature, most often found in the lower back region. These indentations are medically known by different names and can have distinct meanings depending on their location and characteristics. The two most common types are Venus dimples and sacral dimples, with most cases being completely benign. However, in some situations, a back indent can signal a medical issue that warrants professional evaluation.
Understanding the two primary types of back indents
Venus Dimples (Lateral Lumbar Indentations)
Also known as "dimples of Venus" in women and "dimples of Apollo" in men, these are two symmetrical indentations located in the lower back, just above the buttock cleavage.
Cause: They are not caused by muscle or fat, but rather by a short, fibrous ligament that stretches from the posterior superior iliac spine (a part of the hip bone) to the skin. The presence of these dimples is largely hereditary, meaning you are born with them.
Significance: Venus dimples are considered a purely cosmetic feature and are not associated with any medical conditions. Being in good physical shape and having a lower body fat percentage can make them more visible, but they cannot be created through exercise.
Sacral Dimples
A sacral dimple is a single indentation or pit, typically located right above the groove between the buttocks. This is also a congenital condition, meaning it is present at birth.
Cause: The exact cause of sacral dimples is not definitively known, but it is believed to be related to minor abnormalities during fetal development. While most sacral dimples are shallow and harmless, some may be deeper and potentially connected to underlying issues.
Significance: Most sacral dimples do not cause any problems and fade as a child grows. However, a sacral dimple accompanied by certain signs may require a doctor's evaluation to rule out underlying spinal issues. These "red flags" include:
- A nearby tuft or patch of hair
- A skin tag or skin discoloration in the area
- The dimple appears particularly deep or large
Associated conditions and considerations
Sacroiliac (SI) Joint Pain
While Venus dimples themselves are not painful, they are located directly over the sacroiliac (SI) joints, where the sacrum attaches to the ilium of the pelvis. Pain in this region can be caused by problems with the SI joint, which can be mistaken for pain related to the dimples. Causes of SI joint pain include:
- Arthritis
- Traumatic injury
- Pregnancy
- Abnormal walking patterns
Spinal Abnormalities
In rare cases, a sacral dimple can be a marker for an underlying spinal abnormality, such as a neural tube defect. Conditions that may be associated with a sacral dimple include:
- Spina bifida occulta: A mild form of spina bifida where the spinal column doesn't fully close around the spinal cord, though the cord remains within the spinal canal. Most people with this condition have no symptoms. A doctor may use an ultrasound to investigate if a suspicious dimple is present.
- Tethered cord syndrome: A condition where the spinal cord is abnormally attached to surrounding tissue, limiting its movement and potentially causing nerve damage as a child grows. Symptoms can include lower back and leg pain, leg weakness, numbness, and bowel or bladder issues.
When to seek medical advice
It's important to consult a healthcare provider if you or your child has a sacral dimple with any of the associated red flag symptoms mentioned above. For general back pain or discomfort near any back dimples, seek medical attention if you experience:
- Pain that persists for more than a week without improvement
- Pain that radiates down one or both legs
- Numbness, tingling, or weakness in the back, legs, or buttocks
- Unexplained weight loss or fever accompanying back pain
- Difficulty controlling your bladder or bowels
Comparison of Venus Dimples and Sacral Dimples
| Feature | Venus Dimples | Sacral Dimples |
|---|---|---|
| Location | Symmetrical pair on the lower back, above the buttocks | Single dimple or pit, right above the buttock cleavage |
| Cause | Short ligaments tethering skin to the pelvic bone | Congenital development; specific cause is unknown |
| Number | Two, one on each side of the spine | Typically one, but can be multiple or deeper pits |
| Medical Significance | Purely cosmetic and harmless | Usually harmless, but can rarely indicate a spinal issue |
| Associated Pain | Not painful, but overlie the sacroiliac (SI) joints, which can be a source of pain | Not painful on their own, but deep pits can become infected |
| Red Flags | None, as they are benign | Hairy patch, skin tag, discoloration, deep pit |
| Related Conditions | None | Rare association with spina bifida occulta or tethered cord syndrome |
Conclusion
For most people, what do indents in your back mean is simply a benign genetic trait. Symmetrical Venus dimples are a harmless cosmetic feature, while sacral dimples are also typically benign congenital markers. The key is to distinguish between these normal variations and potential warning signs. By being aware of the specific red flag symptoms, particularly those associated with a sacral dimple, you can ensure that any underlying spinal issues are addressed promptly. If you have any concerns about back indentations or experience pain in that area, a consultation with a healthcare provider is the best course of action. More information on sacral dimples can be found on the Cleveland Clinic's website: Sacral Dimple - Cleveland Clinic.
