Sacroiliitis is inflammation within the sacroiliac joint. It is a feature of spondyloarthropathies, such as axial spondyloarthritis (including ankylosing spondylitis), psoriatic arthritis, reactive arthritis or arthritis related to inflammatory bowel diseases, including ulcerative colitis or Crohns disease. It is also the most common presentation of arthritis from brucellosis. Symptoms and signs
People suffering from sacroiliitis can often experience symptoms in a number of different ways, however it is commonly related to the amount of pressure that is put onto the sacroiliac joint. Sacroiliitis pain is typically axial, meaning that the location of the condition is also where the pain is occurring. Symptoms commonly include prolonged, inflammatory pain in the lower back region, hips or buttocks.However, in more severe cases, pain can become more radicular and manifest itself in seemingly unrelated areas of the body including the legs, groin and feet.Symptoms are typically aggravated by:
Transitioning from sitting to standing
Walking or standing for extended periods of time
Running
Climbing stairs
Taking long strides
Rolling over in bed
Bearing more weight on one leg

Cause
Sacroiliitis is a condition caused by inflammation within the sacroiliac joint. This joint is located where the base of the spine, known as the sacrum, and the pelvis, known as the ilium, intersect. "Itis" is a Latin term denoting inflammation.Since sacroiliitis can describe any type of inflammation found within the sacroiliac joint, there can be a number of issues that cause it. These include:
Degenerative arthritis, or osteoarthritis of the spine, can cause degeneration within the sacroiliac joints and lead to inflammation and joint pain.
Endogenous depression (melancholia) is an atypical sub-class of major depressive disorder (clinical depression). It could be caused by genetic and biological factors. Endogenous depression occurs due to the presence of an internal (cognitive, biological) stressor instead of an external (social, environmental) stressor. Endogenous depression includes patients with treatment-resistant, non-psychotic, major depressive disorder, characterized by abnormal behavior of the endogenous opioid system but not the monoaminergic system. Symptoms vary in severity, type, and frequency and can be attributed to cognitive, social, biological, or environmental factors that result in persistent feelings of sadness and distress. Since symptoms are due to a biological phenomenon, prevalence rates tend to be higher in older adults. Due to this fact, biological-focused treatment plans are often used in therapy to ensure the best prognosis.Endogenous depression was part of the Kraepelinian dichotomy system. Signs and symptoms
The forefront indication that a depressive episode is manifesting is the sudden loss of energy or motivation in daily routines. When this occurs, it is not uncommon for individuals to seek medical attention with excessive worrying or anxiety that a more severe, physiological disease may be the underlying issue. However, without an actual disease present, this neurotic thinking often results in severe anxiety, sleep disturbance, and mood swings which may hinder social relationships. Individuals with endogenous depression may experience inconsistencies in symptom severity  which is often the reason for delayed treatment. If left untreated, symptoms may progress to a major depressive episode.