In a patient with knee discomfort but a normal knee examination, can hip pathology refer pain to the knee?

Hip Pathology Frequently Refers Pain to the Knee

Yes, hip pathology is a well-recognized cause of knee pain in patients with normal knee examinations, and must be systematically excluded before attributing symptoms to primary knee pathology. 1, 2

Clinical Recognition Pattern

Hip disease commonly presents with knee pain rather than hip or groin pain, creating a diagnostic trap that leads to misdiagnosis even by musculoskeletal specialists. 3 In one institutional series, 21 patients were referred for knee pain but ultimately diagnosed with hip pathology as the pain source—15 of these referrals came from musculoskeletal providers including 12 from orthopedic surgeons. 3 Twelve patients had already undergone surgical knee interventions, including total knee arthroplasty, with minimal relief before the hip etiology was identified. 3 After hip treatment (primarily total hip arthroplasty), 14 of 17 patients experienced complete resolution of their knee pain. 3

Diagnostic Algorithm for Knee Pain with Normal Knee Examination

Step 1: Obtain Standard Knee Radiographs First

• Order anteroposterior (or Rosenberg/tunnel), lateral, and tangential patellar views of the knee 1, 2
• This establishes baseline imaging and satisfies the requirement that approximately 20% of patients inappropriately receive MRI without recent radiographs 2, 4

Step 2: Perform Directed Hip Assessment

If knee radiographs are normal or show only effusion, immediately evaluate for hip pathology: 1, 2

• Groin pain – the classic location for intra-articular hip pathology 5, 6
• Hip range of motion limitations – particularly internal rotation in flexion 2, 4
• Positive impingement signs – pain with flexion, adduction, and internal rotation 2, 4
• Buttock or lateral thigh pain – may indicate extra-articular hip pathology such as trochanteric bursitis 5, 6
• Pain pattern extending from low back through buttock to thigh and knee – suggests overlapping hip and spine pathology 5, 6

Step 3: Order Hip Radiographs When Clinically Indicated

Obtain pelvis and proximal femur radiographs if any of the following are present: 1

• Clinical evidence of hip pathology on examination 1, 2
• Groin pain or hip range-of-motion restriction 2, 4
• Normal knee radiographs with persistent unexplained knee pain 1, 7

A pelvis view plus additional proximal femur view is superior to isolated ipsilateral hip films for detecting dysplasia, femoroacetabular impingement, and early arthritis. 1

Step 4: Consider Lumbar Spine Evaluation

Also obtain lumbar spine radiographs if: 1, 2

• Low back pain is present 5, 6
• Radicular symptoms suggest nerve root involvement 2, 4
• Pain pattern includes buttock, posterior thigh, and knee 5, 6

Both hip and lumbar spine pathology can coexist and produce overlapping knee pain, requiring sequential management of both conditions. 5, 6

Step 5: Proceed to MRI Only After Excluding Referred Pain

If hip and spine radiographs are normal or not clinically indicated, then order knee MRI without contrast to evaluate for: 2, 4

• Meniscal tears (most common cause of mechanical symptoms) 2
• Articular cartilage defects 2, 4
• Bone marrow lesions (strongly associated with pain) 2, 4
• Ligament injuries 2
• Occult fractures 4, 7

Common Pitfalls and How to Avoid Them

Do not assume knee pain originates in the knee. Hip osteoarthritis, labral tears, femoroacetabular impingement, and other hip pathologies routinely refer pain to the knee, and this remains an overlooked phenomenon despite being considered basic knowledge. 3

Do not order knee MRI before obtaining hip radiographs in patients with normal knee films and clinical suspicion of hip disease. This sequence wastes resources and delays diagnosis. 1, 2

Do not attribute persistent knee pain to "normal aging" or soft-tissue strain without imaging the hip. In the case series, 16 of 21 patients with hip-referred knee pain were reduced to major assistive devices (including wheelchairs) before correct diagnosis. 3

Recognize that both hip and spine pathology may require treatment. Managing one source of pain does not guarantee resolution if the other remains untreated, so counsel patients that sequential interventions may be necessary. 5, 6