Gout is a common form of inflammatory arthritis caused by the accumulation of uric acid crystals within a joint space. While most people associate gout with the sudden, severe pain in the big toe, it is a systemic condition that can affect many joints throughout the body. Gout typically targets smaller, cooler joints, but it can, in rare instances, manifest in larger joints like the hip. This article explores how the condition presents in the hip and how providers distinguish this rare event from other common causes of hip pain.
The Underlying Cause of Gout Flare-ups
Gout results from hyperuricemia, where the concentration of uric acid in the blood rises above its saturation point (approximately 6.8 milligrams per deciliter). Uric acid is a normal waste product from the breakdown of purines. When the body produces too much uric acid or, more commonly, the kidneys do not excrete enough, the excess crystallizes.
These microscopic shards are known as monosodium urate (MSU) crystals, which deposit in the joint tissues. A gout flare is triggered when the immune system recognizes these crystals as foreign invaders. Immune cells flock to the site, causing a massive inflammatory response. This intense immune attack causes the hallmark symptoms of gout: the rapid onset of extreme pain, swelling, heat, and redness in the affected joint.
Gout Manifestation in Large Joints
Gout typically affects peripheral joints like the big toe, ankle, and knee because lower temperatures encourage MSU crystal formation. The hip joint is an atypical site because it is deep, large, warmer, and better perfused with blood, making uric acid more soluble. When gout affects the hip, it usually indicates long-standing, poorly controlled hyperuricemia.
A hip gout flare may not present with the classic acute pain and redness seen in a big toe attack because the joint is deep-seated, making visual signs difficult to detect. Instead, patients experience a severe, deep ache and significant limitation in their range of motion, which can be mistaken for other joint problems. In chronic cases, continuous deposition of urate crystals can lead to the formation of tophi. These chalky deposits can erode the joint cartilage and bone, causing long-term damage and stiffness in the hip.
When Hip Pain Isn’t Gout
It is far more common for a patient with a history of gout to experience hip pain from other musculoskeletal conditions than from an actual gout flare in the hip joint. Healthcare providers must consider these alternative causes, especially since many gout patients have metabolic risk factors that predispose them to other joint problems. Distinguishing the source of the pain is crucial for effective treatment.
Common Alternative Diagnoses
One frequent alternative diagnosis is osteoarthritis (OA), a progressive condition involving the breakdown of the joint’s protective cartilage. Hip OA typically causes a deep, chronic ache felt in the groin, thigh, or buttocks, worsening with activity and improving with rest. Stiffness is common, especially in the morning or after prolonged sitting. The pain is generally progressive over months or years rather than the sudden onset characteristic of an acute gout attack.
Another common cause is trochanteric bursitis, which involves inflammation of the bursa located on the outer side of the hip bone. This condition presents as tenderness and pain on the outside of the hip, often intensifying when lying on the affected side or climbing stairs. Referred pain from the lower back, caused by nerve compression or spinal issues, can also travel to the hip and mimic joint pain.
Diagnosis and Treatment of Hip Gout
Diagnosing gout in a deep joint like the hip requires more than a physical examination and patient history. The definitive method for confirming hip gout is a joint fluid test, also called arthrocentesis. During this procedure, a doctor uses a needle, often guided by imaging, to draw a sample of the synovial fluid from the hip joint. The fluid is then examined under a polarized light microscope to identify the needle-shaped monosodium urate crystals.
Imaging tests, such as X-rays, ultrasound, or dual-energy computerized tomography (DECT), are also used to assess joint damage, visualize crystal deposits, and rule out other causes of pain, like fractures or severe osteoarthritis.
Once hip gout is confirmed, the treatment approach mirrors that for gout in other joints. The acute flare is managed with anti-inflammatory medications, which may include non-steroidal anti-inflammatory drugs (NSAIDs), colchicine, or corticosteroids. For long-term management and prevention of future flares, uric acid-lowering therapy is initiated. Medications like allopurinol or febuxostat reduce the overall level of uric acid in the body, which helps dissolve existing crystals and prevents new deposits from forming.