Assessment of Inflammation of Infrapatellar Fat Pad and its Contribution to Anterior Knee Pain Severity and Severity of Knee Osteoarthritis
Authors: Abd EL Hamid Amira Abd Allah , Kamel Nadia Salah , Elwi Mohammed Ali , Ibrahim Soha Eldessouki 
Published: November 2024

Abstract

Background
Osteoarthritis is the most common arthritic disease worldwide leading to debilitating pain (which is the hallmark symptom of the disease) and destruction of joint tissues. The exact etiopathogenesis of Knee osteoarthritis pain is unclear, but clinical, imaging and biochemical observations indicate that inflammation may contribute to both structural disease progression and pain (consequently disability). Early diagnosis and treatment of the inflammation and its cause may contribute to improve the outcome of the disease.

Aim of the Work
The aim of the study was to assess inflammation of infrapatellar fat pad by musculoskeletal Doppler Ultrasound in knee osteoarthritis patients and its contribution to anterior knee pain severity, and relation to different lines of treatment.

Patients and Methods
This case-control study was conducted on 30 knee osteoarthritis (OA) patients and 30 patients with anterior knee pain without OA. Diagnosis of knee OA is based on American College of Rheumatology clinical and radiographic classification criteria for knee osteoarthritis. Each group of patients was divided into 2 subgroups: Fifteen patients were subjected to weight reduction, NSAID for 2 weeks, and physiotherapy in the form of ultra sound diathermy (US), Trans cutaneous electrical nerve stimulation (TENS), and strengthening exercises for quadriceps muscles. Fifteen patients were subjected to US guided local steroid and anesthetic injection in the infrapatellar fat pad under sterile conditions. The injectate was 40 mg methylprednisolone acetate every 4 weeks for a maximum 3 injections.

Results
Flexion ROM and extension ROM before treatment were insignificantly different between group 1B and group 1A and between group 2B and group 2A while were significantly higher in group 2 (A and B) than group 1(A and B) (p &lt; 0.05). Flexion ROM and extension ROM after treatment were insignificantly different between group 1B and group 1A and between group 2B and group 2A while were significantly higher in group 2B than 1B and in group 1B than group 2A and in group 2A than group 1A (p &lt; 0.05). The lateral recess effusion before treatment was significantly different between the studied groups (p = 0.008) and after treatment was insignificantly different among the studied groups (p = 0.295). Medial femorotibial joint osteophytes before and after treatment was insignificantly different among the studied groups. Femoral cartilage assessment before and after treatment was insignificantly different among the studied groups. Echogenicity before and after treatment was significantly different among the studied groups (p = 0.002 and &lt;0.001 respectively). Hoffa fat pad width before treatment was insignificantly different among the studied groups. Hoffa fat pad width after treatment was significantly different among the studied groups. The Hoffa fat pad width after treatment was significantly lower in group 2B than 1B and in group 1B than group 2A and in group 2A than group 1A (p &lt; 0.05). Largest fat lobule width before treatment was insignificantly different among the studied groups. Largest fat lobule width after treatment was significantly different among the studied groups. Largest fat lobule was significantly higher in group 2B than 1B and in group 1B than group 2A and in group 2A than group 1A (p &lt; 0.05). The Western Ontario and McMaster universities (WOMAC) index before treatment was insignificantly different between group 1A and group 2A, and in group 1B and group 2B while was significantly lower in group 2B and group 1B than group 1A and in group 1B and 2B than group 2A (p &lt; 0.05). The WOMAC index after treatment was significantly different among the studied groups. WOMAC index was significantly lower in group 2B than 1B and in group 1B than 2A and in group 2A than group 1A (p &lt; 0.05). VAS scale before treatment was insignificantly different among the studied groups. VAS scale after treatment was significantly lower in group 2B than 1B and in group 1B than group 2A (p &lt; 0.05).

Conclusion
Inflammation of infrapatellar fat pad is evident clinically in patients with knee osteoarthritis and musculoskeletal US has great role in its diagnosis and treatment by US guided injection. Favorable outcomes were observed by US findings and WOMAC index in patients with no osteoarthritis and taking corticosteroid injections compared to patients with osteoarthritis and taking corticosteroid injections. However, patients with osteoarthritis and taking corticosteroid injections had favorable outcomes compared to osteoarthritis or no osteoarthritis but taking the conventional therapy.

Recommendations
Further largescale clinical studies are needed with multicenter cooperation, and long-term follow-up period to monitor structural changes in both groups is recommended. Relying on musculoskeletal US for early detection of inflammation in Hoffa fat pad, and early treatment by musculoskeletal Us guided local corticosteroid injection may decrease the progression and subsequently the disability of knee OA.