What is the most likely diagnosis for a 53-year-old patient with anterior knee pain that worsens with running and stair climbing?

Most Likely Diagnosis: Patellofemoral Pain Syndrome

The most likely diagnosis for this 53-year-old patient with anterior knee pain that worsens with running and stair climbing is patellofemoral pain syndrome (PFPS).

Clinical Reasoning

The presentation is classic for PFPS based on three key features:

• Anterior knee location: Pain behind or around the patella is the hallmark of patellofemoral disorders, which are strongly associated with anterior knee pain 1
• Activity pattern: Pain that increases with running and stair climbing (both ascending and descending) indicates loading of the knee extensor mechanism during knee flexion under load, which is pathognomonic for PFPS 2
• Age and activity level: While PFPS typically affects those under 40 years, it occurs across all ages and activity levels, making it appropriate for this 53-year-old jogger 3

Supporting Evidence

The British Journal of Sports Medicine defines PFPS as retropatellar or peripatellar pain that worsens with activities requiring knee flexion under load, specifically including stair climbing and running 2. This patient's symptom pattern of pain during jogging 8-10 miles weekly and with stair ambulation precisely matches this definition 4, 3.

PFPS accounts for 11-17% of all knee pain presentations in primary care and is the most common cause of knee pain during stair climbing 2, 3. The gradual onset nature typical of PFPS aligns with this patient's presentation as a recreational jogger rather than acute trauma 4.

Critical Differentials to Exclude

Before confirming PFPS, you must rule out:

• Patellofemoral osteoarthritis: At age 53, early cartilage loss is possible. However, patients 45-55 years with knee pain but normal radiographs can have elevated T2 mapping values on MRI indicating early cartilage changes that still present clinically as PFPS 4
• Patellar tendinopathy: This causes anterior knee pain but typically localizes to the inferior pole of the patella rather than diffuse retropatellar pain 1
• Hip pathology with referred pain: Hip pathology commonly refers pain to the knee and must be evaluated clinically if knee examination is equivocal 1, 2
• Lumbar spine pathology: Must be considered when knee findings are unremarkable, though less likely given the clear activity-related pattern 1, 2

Diagnostic Approach

Initial assessment should include:

• Anteroposterior and lateral knee radiographs to exclude fractures, osteoarthritis, osteophytes, and loose bodies 1, 2
• Palpation for retropatellar or peripatellar tenderness (not isolated joint line tenderness which suggests meniscal pathology) 5
• Assessment for knee effusion—its presence would suggest intra-articular pathology rather than isolated PFPS 5
• Clinical examination of hip and lumbar spine before attributing symptoms solely to knee pathology 1, 2

MRI is not initially indicated unless radiographs show abnormalities or symptoms fail to improve with appropriate treatment 4. Approximately 20% of patients with chronic knee pain undergo premature MRI without recent radiographs, which should be avoided 1.

Common Pitfalls

• Do not overlook referred pain: Hip or lumbar spine pathology can mimic anterior knee pain and should be clinically assessed before focusing solely on the knee 1, 2
• Age considerations: While this patient is older than the typical PFPS demographic, the diagnosis remains valid across all ages, and early patellofemoral osteoarthritis may present identically 4, 3
• Activity modification: The patient's jogging volume (8-10 miles weekly) is moderate, and climbing stairs shows strong evidence for NOT causing knee osteoarthritis, distinguishing it as a pain-provoking activity in existing pathology rather than a causative factor 2