In a 69‑year‑old woman with Parkinson disease, bilateral sciatica, a left total hip arthroplasty and moderate degenerative changes of the right hip who now has right‑hip pain worsened by external rotation and flexion, what is the most likely diagnosis and the recommended work‑up and management?

Right Hip Pain in a Patient with Parkinson's Disease and Degenerative Hip Changes

Most Likely Diagnosis

The most likely diagnosis is symptomatic right hip osteoarthritis with possible femoroacetabular impingement (FAI), given the patient's age, known moderate degenerative changes, and pain pattern worsened by external rotation and flexion. 1

While hip osteoarthritis classically presents with groin pain and internal rotation reproducing symptoms, pain can radiate to the buttock and posterior hip, and the presence of moderate degenerative changes on prior imaging strongly supports this diagnosis 1. The pain with external rotation and flexion also raises consideration for posterior FAI or ischiofemoral impingement 1.

Immediate Diagnostic Work-Up

Obtain AP pelvis and lateral hip radiographs immediately as the first diagnostic step (this is the AAOS-recommended initial imaging for posterior hip pain) 1. These views will:

• Rapidly identify progression of hip osteoarthritis severity 2, 1
• Detect FAI morphology and ischiofemoral space narrowing 1
• Rule out periprosthetic fracture near the contralateral left total hip arthroplasty 2
• Assess for greater trochanter abnormalities or avulsions 2

If plain radiographs are non-diagnostic but clinical suspicion remains high, obtain MRI of the hip without contrast to detect labral tears, early cartilage damage, bone marrow edema, and soft tissue pathology not visible on radiographs 1.

Critical Pitfall to Avoid

Do not assume primary hip joint pathology without imaging confirmation, as referred pain from lumbar spine or sacroiliac joint can mimic hip pathology, particularly in a patient with bilateral sciatica 1. However, given her known moderate degenerative changes and pain pattern, hip pathology remains most likely.

Initial Management Algorithm

Step 1: Initiate NSAIDs Immediately

Start NSAIDs for symptomatic relief (strong recommendation, high-quality evidence for hip osteoarthritis) 2, 1. This provides both diagnostic and therapeutic benefit.

Step 2: Refer to Physical Therapy

Refer to formal physical therapy (moderate recommendation, high-quality evidence) targeting hip muscle strengthening, particularly hip abductors, adductors, flexors, and rotators 2, 1. Either formal PT or unsupervised home exercise is supported after THA, but given her Parkinson's disease and bilateral hip issues, formal PT is preferable 2.

Step 3: Consider Intra-Articular Corticosteroid Injection

Intra-articular corticosteroid injection may be considered for symptomatic relief (moderate recommendation, high-quality evidence) if NSAIDs and PT provide insufficient relief 2, 1.

Medications to Absolutely Avoid

• Do not use oral opioids for treatment of symptomatic hip osteoarthritis (consensus recommendation) 2, 1
• Do not use intra-articular hyaluronic acid injection (strong recommendation, high-quality evidence) 2, 1

Special Considerations for Parkinson's Disease

Functional Outcomes and Timing

Parkinson's disease severity directly impacts outcomes after total hip arthroplasty. Patients with mild Parkinson's disease (Hoehn and Yahr stages I-III) achieve excellent pain relief and functional gains from THA 3, 4, 5, 6. However, functional outcomes are significantly worse in mid- or end-stage PD patients 4.

If conservative management fails and THA is considered, perform surgery while the patient is still in early-stage Parkinson's disease (stages I-III), as neurological status will inevitably deteriorate over time 3, 5, 6. At 36 months post-THA, all elective PD patients in one study walked independently, but by longer follow-up (mean 82 months), only 43% maintained independent walking as PD progressed 6.

Surgical Considerations if THA Becomes Necessary

• Precise surgical technique with optimal implant position and balanced soft tissue tension is critical in PD patients due to excessive muscle tone 3
• Consider cemented femoral fixation in older patients, particularly those with extensive spinal fusion (as this patient has sciatica suggesting possible spinal pathology) 2
• Address instability risk: PD patients have higher rates of dislocation, periprosthetic fractures, and aseptic loosening 7. Consider dual-mobility cups or constrained liners, though evidence is not definitive 7
• Expect longer hospital stays and more medical complications (particularly urinary tract infections and cognitive impairment) compared to non-PD patients 3, 7, 5

Perioperative Risk Profile

Medical complications are common in PD patients undergoing THA, including urinary tract infections (most common), cognitive impairment, and pressure ulcers 3. However, one-year mortality and surgical site infection rates are comparable to controls 7.

Prosthesis survivorship at 60 months is 94.1% for THA in PD patients, which is acceptable though slightly lower than the general population 4.

Clinical Decision Point

The key decision is whether to pursue aggressive conservative management versus early surgical intervention. Given that:

• The patient has moderate degenerative changes already documented 1
• She is 69 years old with Parkinson's disease (likely early-stage given she is ambulatory and presenting to clinic) 3, 4, 5
• Neurological deterioration is inevitable and will worsen surgical candidacy over time 3, 4, 5, 6

If radiographs confirm severe osteoarthritis and conservative measures (NSAIDs, PT, corticosteroid injection) fail to provide adequate relief within 3-6 months, strongly consider proceeding to THA while she remains in early-stage PD 2, 3, 4, 6. Delaying surgery until PD progresses to mid- or late-stage will result in significantly worse functional outcomes 4.

Optimization Before Surgery (If Needed)

Before proceeding to THA, optimize:

• BMI (elevated BMI increases adverse events and lowers patient-reported outcomes) 2
• Hemoglobin A1c if diabetic (poorly controlled diabetes increases adverse event risk) 2
• Discontinue tobacco use (tobacco increases adverse event risk) 2
• Wean off narcotic pain medication under prescribing physician guidance 2

Appropriate counseling is essential: Discuss whether potential improvement in quality of life outweighs the risks of medical complications, longer hospitalization, and inevitable PD progression 7, 6.