Can you interpret the hip/pelvis and knee radiographs of a 76‑year‑old patient with four weeks of insidious groin pain at the femoral‑iliac region, mild lumbar discomfort, and intermittent right‑knee pain aggravated by weight‑bearing, without recent trauma, swelling, or urinary/bowel symptoms?

Radiograph Interpretation for Chronic Hip/Groin and Knee Pain in a 76-Year-Old

You should obtain plain radiographs of the pelvis and hip as the first-line imaging study, followed by knee radiographs if not already performed, as these are the essential initial screening tools for evaluating your chronic groin and knee pain 1, 2.

Initial Imaging Approach

Hip/Pelvis Radiographs (Priority #1)

The ACR Appropriateness Criteria explicitly recommend radiographs of the pelvis and hip as the first test for chronic hip pain 1. For your 4-week history of insidious groin pain without trauma, the standard views should include:

• Anteroposterior (AP) view of the pelvis – This bilateral view is superior to isolated hip films because it allows comparison between sides and evaluates the entire pelvic ring 1
• Frog-leg lateral view of the symptomatic hip 3
• Consider a false profile view if femoroacetabular impingement or dysplasia is suspected 1

These radiographs will screen for:

• Osteoarthritis (most common cause in your age group) – joint space narrowing, osteophytes, subchondral sclerosis
• Occult fractures (stress fractures, insufficiency fractures)
• Osteonecrosis of the femoral head
• Bone tumors (less common but important to exclude)
• Hip dysplasia or impingement patterns

Knee Radiographs

For your intermittent right knee pain, obtain at least three views: anteroposterior, lateral, and tangential patellar view 2. The ACR guidelines emphasize that approximately 20% of patients with chronic knee pain inappropriately receive MRI without recent radiographs 2.

Knee films will evaluate for:

• Osteoarthritis (extremely common at age 76)
• Chondrocalcinosis (calcium pyrophosphate deposition)
• Osteochondral lesions
• Joint effusion

Critical Diagnostic Consideration: Referred Pain

Your combination of groin pain, lumbar discomfort, and knee pain raises the possibility of referred pain from the hip or spine 2, 4. This is a common diagnostic pitfall:

• Hip pathology frequently refers pain to the knee – The ACR guidelines specifically state that hip radiographs should be considered in patients with chronic knee pain when knee films are unremarkable 2
• Lumbar spine pathology can mimic hip pain – Your "standard lumbar discomfort" may be contributing to or causing the groin symptoms 4
• Overlapping symptoms are common in patients with both hip and spine pathology, often delaying correct diagnosis 4

What the Radiographs Will Tell You

If Radiographs Show Osteoarthritis:

Physical examination and radiography may be sufficient without MRI, as they have reasonable sensitivity and specificity for osteoarthritis 1. At age 76, degenerative changes are expected and often correlate with symptoms.

If Radiographs Are Normal or Equivocal:

MRI without IV contrast becomes the next appropriate study 1, 2. MRI is highly sensitive and specific for:

• Soft tissue pathology: iliopsoas tendinopathy/bursitis, adductor strains, trochanteric bursitis, abductor tears 1, 5
• Labral tears (though these require MR arthrography for optimal detection) 1
• Occult fractures: stress fractures, subchondral insufficiency fractures 1, 2
• Bone marrow edema: associated with pain in osteoarthritis 2
• Cartilage defects and early degenerative changes not visible on X-ray

For the Knee Specifically:

If knee radiographs are normal but pain persists, MRI without IV contrast is the next indicated examination 2. However, be aware that meniscal tears are incidental findings in the majority of people over 70 years old and may not be the pain source 2.

Important Caveats

Age-related findings do not always correlate with symptoms:

• Asymptomatic meniscal tears are present in most patients over 70 2
• Structural joint changes on MRI are frequent in asymptomatic populations 6
• Neither radiographs nor MRI show perfect correlation with pain and functional impairment 6

Red flags to exclude (though you report none):

• Fever, weight loss, night pain (malignancy, infection)
• Urinary/bowel symptoms (cauda equina, pelvic pathology)
• Acute trauma with inability to bear weight (fracture)

Algorithmic Approach to Your Case

1. Obtain pelvis/hip radiographs first (AP pelvis + frog-leg lateral) 1
2. Obtain knee radiographs (AP, lateral, patellar views) 2
3. If both are normal or show only mild osteoarthritis:
   • Consider diagnostic hip injection (anesthetic ± corticosteroid) to determine if hip is the pain source 1, 7
   • This can differentiate hip pain from referred lumbar or knee pain
4. If injection provides relief: Hip is confirmed as pain source; proceed with hip-directed treatment
5. If injection provides no relief or radiographs are equivocal: Obtain MRI hip without IV contrast 1
6. If knee pain persists with normal knee films: Obtain MRI knee without IV contrast 2

Ultrasound is an alternative for evaluating soft tissue structures (bursitis, tendinopathy, effusions) and can guide injections, but it is not comprehensive for screening 1, 8.

Your cautious approach to returning to swimming is appropriate—low-impact exercise is generally safe while awaiting imaging interpretation, but avoid high-impact activities until the diagnosis is clarified.