What is the appropriate treatment algorithm for infrapatellar fat‑pad impingement (Hoffa’s disease)?

Infrapatellar Fat Pad Impingement (Hoffa's Disease): Treatment Algorithm

Begin with a 6-8 week trial of conservative management consisting of NSAIDs, activity modification, physical therapy focused on quadriceps strengthening and patellar mobilization, and consider ultrasound-guided corticosteroid injection into the fat pad; if symptoms persist despite optimal conservative treatment, proceed to arthroscopic partial or subtotal fat pad resection. 1, 2, 3

Initial Conservative Management (First-Line Treatment)

Diagnostic Confirmation

• Confirm diagnosis with MRI showing fat pad edema, hypertrophy, or synovitis thicker than 2 mm, which correlates with peripatellar pain 1
• Contrast-enhanced MRI is more accurate for diagnosing Hoffa's disease and quantifying the degree of synovitis 1
• Physical examination should demonstrate positive Hoffa's test (tenderness with palpation of the fat pad on either side of the patellar tendon with the knee extended) 3
• Consider diagnostic lidocaine injection into the fat pad—symptom relief confirms the diagnosis 3

Conservative Treatment Protocol (6-8 Weeks Minimum)

• Prescribe NSAIDs for anti-inflammatory effect targeting the inflamed fat pad 2, 4
• Initiate physical therapy emphasizing quadriceps strengthening exercises to improve patellar tracking and reduce fat pad impingement 2, 4
• Include patellar mobilization techniques to prevent adhesion formation between the fat pad and surrounding structures 2, 4
• Modify activities to avoid repetitive knee flexion-extension movements that cause fat pad impingement 4, 5
• Consider ultrasound-guided corticosteroid injection into the inflamed fat pad if initial measures fail after 3-4 weeks 5

Alternative Conservative Option: Ultrasound-Guided Alcohol Ablation

• For patients who fail standard conservative measures but wish to avoid surgery, consider ultrasound-guided alcohol ablation of the fat pad 5
• This involves injecting a mixture of alcohol and local anesthetic under ultrasound guidance, with repeat injections at three-weekly intervals (mean of 4 injections) 5
• This technique achieved 62% reduction in pain scores in a pilot study with minimal side effects 5
• This represents an intermediate step between conservative management and surgical intervention 5

Surgical Intervention (When Conservative Treatment Fails)

Indications for Surgery

• Persistent symptoms after minimum 6-8 weeks of optimal conservative management including medications, physical therapy, and injections 2, 3
• MRI-confirmed fat pad pathology with clinical correlation 3
• Positive response to diagnostic lidocaine injection confirming fat pad as pain source 3

Arthroscopic Technique

• Perform arthroscopic partial or subtotal resection of the infrapatellar fat pad using a superolateral viewing portal for excellent visualization 2
• Remove impinged, fibrotic, or hypertrophic portions of the fat pad that are causing mechanical symptoms 2, 4
• Address any associated fibrocartilaginous transformation or early ossification that may develop from chronic impingement 6
• Subtotal resection is preferred over complete removal to preserve some fat pad function 2, 3

Expected Surgical Outcomes

• Long-term follow-up (mean 148.7 months) demonstrates sustained clinical improvement with VAS scores decreasing from 7.25 preoperatively to 3.66 at final follow-up 3
• Significant improvements in Kujala, IKDC-2000, Lysholm, and Tegner activity scores are maintained at 10-year follow-up 3
• Radiographic parameters remain stable with no significant progression of patellofemoral osteoarthritis after fat pad resection 3
• However, 27.8% of patients report persistent symptoms at long-term follow-up, emphasizing the importance of accurate diagnosis 3

Critical Pitfalls to Avoid

• Do not proceed to surgery without adequate conservative trial: A minimum 6-8 week trial of comprehensive conservative management must be completed first 2, 3
• Do not rely on plain radiographs alone: X-rays are often normal in Hoffa's disease; MRI is essential for diagnosis 1
• Do not perform complete fat pad excision: Subtotal resection preserves some fat pad function and is the preferred technique 2, 3
• Do not misdiagnose as patellofemoral pain syndrome: While both cause anterior knee pain, Hoffa's disease has specific MRI findings of fat pad pathology and responds to targeted fat pad injection 1, 3
• Do not ignore the acute phase: Early recognition and treatment of acute fat pad impingement prevents progression to chronic fibrosis and ossification 4, 6