A 62-year-old woman with six months of anterior knee pain, no history of trauma, worse with stair climbing, patellar tenderness, and obesity (BMI 46). Which diagnosis is most likely?

A 62-year-old woman with six months of anterior knee pain, no history of trauma, worse with stair climbing, patellar tenderness, and obesity (BMI 46). Which diagnosis is most likely?

• A. Chondromalacia patella
• B. ACL tear
• C. Medial meniscus tear
• D. Prepatellar bursitis

Answer: (D)

Anterior knee pain with focal tenderness directly over the patella points to irritation of the structures in front of the knee rather than inside the joint. The prepatellar bursa sits right in front of the patella, and inflammation here—prepatellar bursitis—produces tenderness and sometimes swelling in that area. This fits well with a nontraumatic course and a risk factor present in this patient: obesity, which adds repetitive pressure to the knee as it bends during activities like stair climbing. The pain worsens with knee flexion because bending the knee compresses the inflamed bursa against the patella and skin. Chondromalacia patellae (softening of cartilage under the patella) can cause anterior knee pain and is more common in younger individuals or athletes; it often presents with crepitus and pain on patellar tracking rather than a localized bursal swelling. ACL tear would typically follow an acute twisting injury and present with instability and immediate swelling, not chronic anterior patellar tenderness. Medial meniscus tear usually causes joint line tenderness, swelling, and mechanical symptoms like locking or clicking, again not a localized prepatellar process. So the pattern of chronic anterior knee pain with tenderness over the patella and risk from obesity, without trauma or mechanical symptoms, makes prepatellar bursitis the most likely diagnosis.

Anterior knee pain with focal tenderness directly over the patella points to irritation of the structures in front of the knee rather than inside the joint. The prepatellar bursa sits right in front of the patella, and inflammation here—prepatellar bursitis—produces tenderness and sometimes swelling in that area. This fits well with a nontraumatic course and a risk factor present in this patient: obesity, which adds repetitive pressure to the knee as it bends during activities like stair climbing. The pain worsens with knee flexion because bending the knee compresses the inflamed bursa against the patella and skin.

Chondromalacia patellae (softening of cartilage under the patella) can cause anterior knee pain and is more common in younger individuals or athletes; it often presents with crepitus and pain on patellar tracking rather than a localized bursal swelling. ACL tear would typically follow an acute twisting injury and present with instability and immediate swelling, not chronic anterior patellar tenderness. Medial meniscus tear usually causes joint line tenderness, swelling, and mechanical symptoms like locking or clicking, again not a localized prepatellar process.

So the pattern of chronic anterior knee pain with tenderness over the patella and risk from obesity, without trauma or mechanical symptoms, makes prepatellar bursitis the most likely diagnosis.