3. DISCUSSION
OC is a benign tumor of bone tissue that occurs mainly during
endochondral ossification of growth plates of long bones. OC is often
caused by hereditary multiple exostoses in the areas of the tibiofemoral
and patellofemoral joints (6). Of course, this lesion is rarely observed
in the patellar ligament and usually causes stiffness of the knee joint
(joint locking), dysfunction of the anatomic function of the quadriceps
femoris muscle tendon and loss of knee joint extension, edema, chronic
pain, ossification of the ligament, formation of fibro- fatty tissue,
degenerative arthritis and finally neurovascular compression (7).
In the present case, the patient presented with common symptoms of OC,
including edema, chronic pain and stiffness in the knee joint and
palpation of solid masses in the patellar ligament. These symptoms could
be due to the inflammatory processes involved in the degeneration of
dense connective tissue around the mass of exostoses in the lacunae of
the patellar ligament. Studies show that OC is associated with good
prognosis and low risk of metastasis, but due to the disturbance in the
anatomical alignment of the knee joint, the masses are removed by
radical resection and the patellar ligament is fixed and stabilized at
the connection to the tibial tuberosity (5). In the report of Pandian et
al. (2016), in a 22-year-old man, bilateral OC masses in the patella and
patellar ligament caused severe arthritis, chronic pain, edema, and
impaired flexion-extension knee movements (8). In 15% of cases, the
mass is surrounded by a calcified cartilage cap around the bony lacuna,
and its thickness even reaches >15 mm (4). Studies show
that the incidence ranges of OC are 0.9 - 1.4% per 100,000, which is
rare in the patellar ligament. If there is no intervention, valgus
deformity in the ankle, knee and pelvic joints is expected in the third
decade of life. However, vascular compression and/or nerve compression
along with acute pain, extensive edema and tissue degeneration are
observed in OC of the hip (sacroiliac-iliofemoral) and shoulder
(glenohumerus) joints (9 and 10).