Hip osteoarthritis: where is the pain?

Background: Pain radiating below the knee is typically thought to originate from the lumbosacral spine rather than degenerative hip pathology. We investigated the lower limb distribution of pain using body image maps in 60 patients awaiting primary hip arthroplasty and in 60 patients awaiting spinal decompression for confirmed spinal stenosis. The perception of 33 orthopaedic registrars regarding distribution of hip pain was also assessed. Results: Groin and buttock pain are significantly more common in hip osteoarthritis. The presence of groin pain is 84.3% of those sensitive for hip dysfunction with a specificity of 70.3%. Patients with hip osteoarthritis had pain below the knee in 47% of cases whereas 88.5% of orthopaedic trainees believed hip pain did not radiate below the knee. Radiographic features of osteoarthritis within the hip joint, visual analogue pain score or Oxford Hip Score have no significant association with a patient's distribution of hip pain. Conclusions: Hip pain referred below the knee is common with a degenerate hip joint and follows the distribution of the saphenous nerve, which branches from the femoral nerve. Radiographic deterioration of a hip joint does not correlate with pain distribution or patient dysfunction as measured by the Oxford Hip Score.