What is Patellar Enthesopathy?
Patellar enthesopathy is a degenerative disorder of the patellar tendon at its attachment site to the inferior pole of the patella, characterized by activity-related anterior knee pain resulting from repetitive loading rather than inflammation. 1
Pathophysiology
The condition involves tendinosis—a degenerative process with microinjury to tendon fibers, mucoid degeneration, necrosis, and loss of transitional fibrocartilage—not tendinitis (inflammation), making the term "patellar tendinitis" technically incorrect. 2, 3
Repetitive loading of the patellar tendon, particularly from jumping activities, generates considerable energy loads in the extensor mechanism that lead to progressive tendon dysfunction. 2
Clinical Presentation
Patients experience activity-related anterior knee pain localized at the inferior pole of the patella that worsens with navigating stairs and prolonged sitting. 1
The condition affects both athletes (especially those in jumping sports like basketball and volleyball) and non-athletes alike. 1, 2
Pain typically develops gradually and can persist for years if untreated, sometimes ending athletic careers despite prolonged treatment attempts. 4
Physical Examination Findings
Tenderness at the inferior pole of the patella with the leg fully extended during resisted leg extension is the hallmark finding. 1, 5
The decline squat test reproduces pain by placing increased load on the patellar tendon. 1, 5
In more advanced cases, palpable tendon thickening and nodules may be present. 1
Diagnostic Imaging
Ultrasonography demonstrates high specificity (94%) but lower sensitivity (58%) for showing tendon thickening and decreased echogenicity. 5
MRI shows moderate sensitivity (78%) and specificity (86%) for demonstrating chronic degenerative changes. 5
MRI with metal reduction techniques can evaluate patellar tendinopathy in patients with total knee arthroplasty. 1
Ultrasound can effectively evaluate patellar tendinopathy in the post-surgical setting. 1
Key Clinical Distinction
This is fundamentally a degenerative overuse condition, not an inflammatory process, which has critical implications for treatment selection—anti-inflammatory medications provide only short-term pain relief without affecting long-term outcomes. 1, 5
The pathology involves mucoid degeneration and necrosis rather than active inflammation, explaining why traditional anti-inflammatory approaches have limited efficacy. 3