Orthopedics - Oleksa A.P. 2006

Congenital and Acquired Deformities of the Lower Extremity
Congenital Deformities of the Knee Joint
Baker's Cyst

Arthritis of any Etiology is typically accompanied by an exudative process manifested by excessive fluid accumulation within the joint cavity. Due to the underlying joint pathology and increased intra-articular pressure, patients experience heightened joint pain. A protective antalgic contracture develops, balancing the tension of antagonistic Muscles and making the joint appear more voluminous, which eases the patients' condition. In chronic synovitis, during movement and joint loading, the excessive fluid distends the fibrous-synovial capsule and widens the joint space, given that joint cavities, with the exception of the knee, are enclosed spaces.

The knee joint cavity communicates via a very narrow channel with the bursa musculi semimembranosi and the upper anterior recess of the knee, which is sometimes isolated and does not communicate with the joint cavity.

When there is an excess of exudate and elevated pressure within the knee—most commonly observed in patients with rheumatoid arthritis during the early stage of the disease—flexion of the lower leg forces the fluid out of the joint cavity, driven by the taut tendon of the rectus femoris Muscle and the Patella, into the semimembranosus bursa, which is the most compliant area of the popliteal fossa. Gradually, fluid accumulates within this bursa, forming a Baker's cyst, which can vary in size and even extend into the canalis cruropopliteus (Fig. 175), thereby deforming the area of the triceps surae muscle.

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Fig. 175. Baker's popliteal cyst in rheumatoid synovitis: a — clinical appearance, b — radiograph following contrast agent administration.

Small popliteal cysts cause little discomfort to patients, and they may go unnoticed.

We observed a patient with Rheumatoid Polyarthritis who felt a click and pain in the popliteal fossa during a deep squat (therapeutic exercise). Her rheumatologist referred her to a surgeon, who diagnosed thrombophlebitis due to subsequent lower leg edema. However, the prescribed Surgical Treatment was ineffective, and the calf pain intensified sharply, prompting the patient to seek our care. Based on her medical history and contrast arthrography of the knee joint (with contrast agent leaking from the joint cavity into the canalis cruropopliteus), a Diagnosis of ruptured popliteal cyst was established.

The patient underwent synovicapsulectomy of the knee joint affected by the rheumatoid process. Under comprehensive treatment, the symptoms of aseptic reactive inflammation in the lower leg completely disappeared.

Quite often, surgeons fail to associate The Development of a Baker's popliteal cyst with arthritis and surgically excise only the cyst itself.

We had to operate on a patient three months after cyst excision due to chronic synovitis and recurrence of the popliteal cyst. Following synovicapsulectomy, the popliteal cyst resolved completely.

Serial contrast radiographs confirmed that after joint synovicapsulectomy, popliteal cysts decrease in size, fibrin clots formed within the cyst undergo fibrosis, and the cystic cavity obliterates. Therefore, synovectomy is pathogenetically justified in all cases of popliteal cysts. In cases of large popliteal cysts, their excision must be performed simultaneously with joint synovicapsulectomy, as fibrosis takes a considerable amount of time, and sometimes they may become encapsulated and persist.