Background The enthesis around the knee including the quadriceps tendon and infrapatellar ligament insertions could be responsible for a significant cause of knee pain functional deterioration in long standing knee osteoarthritis.
Objectives Ultrasound evaluation of the enthesis at the quadriceps tendon patellar insertion, infrapatellar ligament patellar and tibial insertions in patients with long standing knee osteoarthritis (KOA) and low knee function.
Methods 410 Patients with KOA attending the outpatient rheumatology clinic of AL-Azhar university hospitals who had met the inclusion criteria:
Primary Knee osteoarthritis.
Kellegren – Lawrance scale grade III.
At least 5 years disease duration.
Patients with chronic diseases affects the patient function.
Patients with previous knee surgery, recent trauma, or intraarticular intervention.
Patients with knee effusion, active synovitis, or popliteal cysts.
All patients were subjected to ultrasound assessment in gray scale and Power Doppler was performed using a scanner with a multifrequency 12L linear array transducer (General electric Systems; LOGIQU-E). Ultrasound techniques were used for all patients included in the study. Knee was assessed for the following items in both sides while Patient lying supine with the knee flexed 40 degrees:
1) Superior pole of the patella – quadriceps tendon enthesis: ● Quadriceps tendon thickness >6.1 mm ● Suprapatellar bursitis ● Superior pole of patella erosion ● Superior pole of patella enthesophyte.
2) Inferior pole of the patella – proximal patellar ligament enthesis: ● Patellar ligament thickness >4 mm ● Inferior pole of patella erosion ● Inferior pole of patella enthesophyte.
3) Tibial tuberosity – distal patellar ligament enthesis ● Patellar ligament thickness >4 mm ● Infrapatellar bursitis ● Tibial tuberosity erosion ● Tibial tuberosity enthesophyte.
Knee functional status was assessed using KOOS scale for Pain, other Symptoms, Activities of Daily Living (ADL), Sport and Recreation Function (Sport/Rec) and knee-related Quality of Life (QOL). Low knee function was considered if the patient had score 50 or more in any KOOS scale parameter.
Results 172 (42%) patients were found with low knee function among them quadriceps enthesitis found in 114 (66.3%) patients, at the patellar attachment of infrapatellar ligament in 160 (93%) patients, and enthesitis at the tibial attachment of infrapatellar ligament in 44 (26%) patients. Good knee function were found in 238 (58%) patients among them quadriceps enthesitis found in 76 (31.9%) patients, at the patellar attachment of infrapatellar ligament in 87 (36.3%) patients, and no enthesitis at the tibial attachment of infrapatellar ligament were detected.
Conclusions Enthesitis at the quadriceps and infrapatellar ligament represent a common ultrasonographic finding in patients with longstanding KOA, and significantly associated with low knee function.
Disclosure of Interest None declared