PIGMENTED VILLONODULAR SYNOVITIS
AND MENISCAL CYSTS
PIGMENTED VILLONODULAR SYNOVITIS
This diffuse or localized lesion develops in synovial
tissue and involves the joints, bursae, and tendon sheaths. Although its
etiology remains unclear, it does appear to be an idiopathic condition.
Diffuse Villonodular Synovitis
This condition typically occurs in adults between 20 and 40 years of age. A single joint of the lower limb, most frequently the knee, is the most common site of involvement. The synovial membrane becomes thickened and diffusely covered with long, tangled, reddish and yellow-brown villi, which may mat together to form plaques. Later, both sessile and pedunculated rubbery nodules appear. Hemosiderin-bearing stromal cells, lipid-bearing foam cells, and multinucleated giant cells are seen on microscopic examination.
Late in the disease, the pathologic changes may cause
pressure indentation of bone and sometimes actual invasion of bone at the
articular margins with subsequent bone destruction.
The predominant symptom is a chronic, slowly
increasing swelling of the joint that is associated with mild aching. Acute
episodes of pain with increased joint swelling may occur intermittently and are
attributed to pinching of villi between the joint surfaces, with subsequent
hemorrhage. Because the course of the disease is usually benign, diagnosis and
treatment are often delayed. Examination of a palpable joint often shows a
diffuse, slightly warm and tender, boggy swelling. A valuable diagnostic
finding is the aspiration of bloody, brown, or serosanguineous fluid from a
chronically swollen, uninjured joint.
Early on, radiographic examination may reveal an increase in joint fluid and a thickened synovial membrane.
However, MRI remains the diagnostic imaging modality that is most beneficial.
Late in the disease, superficial erosions of cortical bone near the joint
margin and irregular areas of bone destruction may be present. Surgical
treatment options range from arthroscopic synovectomy for more mild or inactive
forms to complete open synovectomy for active diffuse forms. If the entire
synovial membrane cannot be excised, localized disease can recur and radiation
therapy may be indicated. If bone destruction is present, a total joint
arthroplasty can be performed.
Localized Villonodular Synovitis
This more common form occurs in small joints, bursae,
and tendon sheaths. The characteristic lesion is a sessile or pedunculated,
yellow to reddish brown nodule with localized villous proliferation around its
base. Symptoms are mild, consisting of intermittent swelling and aching. Slight
swelling and a localized nodule may be noted on examination. The tenosynovitis,
also called a xanthomatous giant cell tumor of the tendon sheath, is the most
common manifestation of localized villonodular synovitis, occurring primarily
in the hand or foot, where it presents as a discrete, firm, slowly enlarging
nodule.
Treatment is complete excision of the nodular lesions
in joints, tendon sheaths, and bursae.
MENISCAL CYSTS
Cysts of the meniscus of the knee are one of the most
frequent causes of swelling at the lateral or medial joint line. The lateral
meniscus is involved much more
frequently than the medial meniscus. Although the
etiology of these cysts is unknown, they may be due to trauma that causes
cystic or mucoid degeneration in fibrocartilage and fibrous tissue and are
often associated with tears of the meniscus. Patients vary in age from
adolescence to middle age.
The cysts normally develop in the periphery of the
middle third of the meniscus and in the adjacent soft tissues within the joint
capsule. Usually multilocular and lined with endothelium, they contain a clear,
gelatinous material.
Persistent aching in the cyst area is the main symptom. Examination reveals a tense, palpable, and often visible swelling at the joint line over the middle third of the meniscus, usually just anterior to the LCL. The cyst, which moves with the tibia, is most prominent on extension of the knee and tends to disappear on flexion. Arthroscopic examination and decompression of the cyst, while addressing any meniscal pathology, is indicated if pain and disability are significant.
