Post-Traumatic Hip Arthritis

Even when a hip fracture or dislocation is reduced perfectly and heals completely, the cartilage may have been irreparably damaged at the moment of injury. Chondrocytes (cartilage cells) die in the zone of impact, the matrix that supports them is disorganised, and small changes in joint congruity persist long after the fracture itself has consolidated. These changes accumulate quietly until, years later, the patient develops the familiar symptoms of hip arthritis.

Several mechanisms contribute:

• Direct cartilage damage at impact. The single biggest driver. Chondrocyte death and matrix damage cannot be reversed by even perfect surgical reduction.
• Articular incongruity. Imperfect reduction leaves a small step in the joint surface. The strongest single predictor is reduction quality: more than 2 millimetres of residual step-off raises post-traumatic arthritis risk to over 40 per cent compared with around 13 per cent for anatomic reduction (Matta).
• Altered joint mechanics. Malunion, leg length discrepancy, or residual instability concentrate stress on certain parts of the cartilage.
• Retained hardware. Plates, screws, or nails can irritate soft tissues and complicate any eventual hip replacement.
• Post-traumatic avascular necrosis. Particularly after femoral neck fractures or posterior hip dislocations. Loss of blood supply to the femoral head leads to bone collapse and rapid secondary arthritis.
• Heterotopic ossification. Extra bone forming in soft tissues after the original surgery, sometimes restricting motion and complicating the joint.

Around 1 in 5 patients develops severe arthritis at 10 to 20 years after surgical acetabular fixation, and the figure exceeds 40 per cent when the fracture could not be reduced anatomically. Femoral neck fractures carry a 15 to 50 per cent risk of avascular necrosis driving secondary arthritis. Traumatic hip dislocations carry around 24 per cent risk of arthritis at 10 years in uncomplicated cases.

The risk of post-traumatic arthritis depends heavily on the type and severity of the original injury and how well it was reduced surgically:

• Acetabular fracture. A break of the hip socket, usually caused by high-energy trauma (road traffic collision, fall from height, motorcycle crash). Around 19 per cent of patients develop severe arthritis at 10 to 20 years after surgical fixation. The Matta studies showed reduction within 2 millimetres of anatomic gives only 13 per cent risk, while greater than 2 millimetres step-off raises this above 40 per cent.
• Femoral neck fracture. Particularly displaced fractures in younger patients, where surgical fixation is attempted rather than replacement. The neck fracture can disrupt the blood supply to the femoral head, causing avascular necrosis in 15 to 50 per cent of patients, with subsequent collapse and secondary arthritis.
• Traumatic hip dislocation. Particularly posterior dislocations from high-energy injuries. Up to 24 per cent develop arthritis at 10 years even after prompt reduction; the rate rises sharply if reduction was delayed beyond 6 to 12 hours or if there is an associated acetabular fracture.
• Femoral head fracture. Pipkin fractures, often associated with dislocation. High risk of post-traumatic arthritis because of direct articular cartilage damage.
• Severe sports impaction injuries. Bone bruise patterns and chondral shear injuries from rugby, football, skiing, and similar high-impact sports can produce post-traumatic arthritis years later, even when the original X-rays appeared normal.
• Childhood or adolescent hip trauma. Injuries during skeletal maturity can alter joint shape and produce post-traumatic arthritis decades later in adulthood.

The condition is essentially primary osteoarthritis on a fast track, triggered by a defined injury rather than gradual wear.

Conservative care is appropriate first-line treatment for post-traumatic hip arthritis as it is for primary osteoarthritis. The same NICE NG226 framework applies:

• Therapeutic exercise. Tailored physiotherapy combining strengthening, range-of-motion work, and aerobic exercise. Particularly useful for soft tissue contractures from prior surgery.
• Weight management. Reducing joint loading slows symptom progression.
• Topical NSAIDs. Preferred over oral NSAIDs because of fewer systemic side effects.
• Oral NSAIDs. Used at the lowest effective dose for the shortest duration.
• Image-guided intra-articular injection. Both diagnostic (confirms the hip as the source of pain rather than retained hardware or scar tissue) and therapeutic (provides several months of symptom control). Particularly useful in younger post-traumatic patients to buy time before surgery.

The key difference from primary arthritis is the timeline. Post-traumatic patients are typically younger and more active, so the threshold of conservative care that they will tolerate is lower. They want to keep working, keep doing sport, keep playing with children. Hip replacement is more often offered earlier in the disease course than for an older patient with primary osteoarthritis.

If you take prescribed medication, particularly blood-thinners or anti-inflammatories, please review Mr Hussain's patient guide on medications to pause before hip or knee surgery as you approach a surgical decision.

Mr Hussain trained in both hip replacement and hip resurfacing and tailors the choice to the individual. For post-traumatic patients the resurfacing option is more constrained than for primary osteoarthritis because the original injury often disqualifies the femoral head from being resurfaced safely.

For a deeper comparison of the two techniques covering recovery, return to sport, and implant choice, read Mr Hussain's patient guide on hip resurfacing versus total hip replacement. Active patients considering resurfacing may also find returning to sport after hip resurfacing useful for setting realistic expectations.