Hip Osteoarthritis: Understanding Joint Degeneration and Staying Active

What Is Hip Osteoarthritis?

Osteoarthritis (OA) of the hip is a degenerative joint disease characterised by progressive loss of articular cartilage, subchondral bone remodelling, osteophyte formation, and synovial inflammation. The hip joint — a ball-and-socket articulation between the femoral head and the acetabulum — is one of the most commonly affected weight-bearing joints in the body, with hip OA affecting approximately 10% of adults over 60. Unlike the inflammatory arthropathies, hip OA is not primarily an immune-mediated disease: it arises from an imbalance between cartilage degradation and repair, driven by mechanical loading, biochemical factors, and the progressive failure of the joint's protective mechanisms. Once established, hip OA follows a variable course — some individuals progress slowly over decades with manageable symptoms; others experience rapid cartilage loss and debilitating disability within a few years.

What Happens Inside the Joint

Articular cartilage has limited regenerative capacity — it is avascular and aneural, sustained by diffusion of nutrients from synovial fluid. When the balance of mechanical loading and repair capacity is disrupted — by age-related changes in chondrocyte function, prior injury, obesity, or repetitive overloading — the cartilage matrix begins to break down. Chondrocytes release matrix metalloproteinases that degrade collagen and proteoglycans, the structural components of cartilage. The progressive loss of cartilage exposes subchondral bone, which undergoes sclerosis (hardening) and cyst formation. The joint margins develop osteophytes — bony outgrowths that represent the joint's attempt to redistribute load across a reduced articular surface. The synovium, irritated by cartilage debris, produces low-grade inflammatory cytokines that amplify pain and accelerate further degradation. Pain in established OA arises not from cartilage (which is aneural) but from the subchondral bone, synovium, joint capsule, and periarticular muscles and tendons.

Recognising Hip Osteoarthritis

Hip OA classically presents with deep groin pain — occasionally referred to the anterior thigh or knee — that is aggravated by weight-bearing activity and eased by rest in the early stages. Morning stiffness of less than 30 minutes duration (distinguishing it from inflammatory arthritis) is typical. As the condition progresses, pain occurs at rest and at night, and the characteristic gait pattern emerges: an antalgic gait with reduced hip extension and a Trendelenburg sign (hip drop) from gluteus medius weakness. Loss of internal rotation is the earliest and most reliable physical sign of hip OA. The FADIR test (flexion-adduction-internal rotation) is positive in most presentations. Hip OA commonly refers pain to the knee — a feature that can delay diagnosis if the hip is not specifically assessed.

Exercise as Medicine

Exercise is the most strongly evidence-supported intervention for hip OA — more effective than analgesics for improving function and quality of life, and the only intervention consistently shown to modify the disease course over time. The mechanism is multifactorial: exercise improves cartilage nutrition through joint movement and load cycling; strengthens periarticular muscles (particularly the gluteals and hip external rotators) that reduce peak joint contact forces; improves neuromuscular control; and reduces the systemic inflammatory burden through metabolic effects. Effective programmes combine progressive resistance training (targeting hip abductors, extensors, and external rotators through functional loading), aerobic exercise (water-based exercise reduces load while maintaining cardiovascular and muscular benefits), and neuromuscular training (balance and proprioceptive exercises that improve joint centring under load). Pain during exercise should be monitored using a 0–10 scale — up to 4/10 is acceptable and not harmful; activity that consistently provokes pain above this level requires modification.

Comprehensive Management

Exercise remains central, but comprehensive management incorporates several additional strategies. Weight management — even modest reductions in BMI substantially reduce hip joint load and symptom severity. Education and self-management support — understanding OA as a modifiable condition rather than inevitable deterioration markedly improves adherence and outcomes. Footwear and orthotics modify lower limb mechanics and reduce provocative loading. Manual therapy — hip joint mobilisation, soft tissue release of the hip capsule, piriformis, and iliopsoas, and thoracolumbar and lumbar mobilisation — reduces pain, improves range of motion, and facilitates exercise participation. Total hip arthroplasty — hip replacement — is among the most successful elective surgical procedures, achieving excellent pain relief and functional restoration in appropriate candidates when conservative management has failed.