Natural course of Baker’s cysts in a total knee arthroplasty population

AIMS AND OBJECTIVES: Baker’s cysts are known to be a source of discomfort and pain due to pressure on adjacent structures. They are not uncommon in patients eligible for total knee arthroplasty (TKA). Since there is a paucity of medium-term studies that assess the natural course of Baker’s cyst following TKA, in this study we report the one- and five-year outcomes of patients to elucidate the state of their Baker’s cyst following TKA. MATERIALS AND METHODS: In this prospective case series, 102 TKA patients were included. All patients who received surgery had a diagnosis of primary osteoarthritis and had preoperatively presented with a Baker’s cyst. Sonography was performed to evaluate the existence and the gross size of the cyst before TKA, and sonography was repeated at one and five years after TKA. Symptoms potentially attributable to the Baker’s cyst were recorded at each assessment. In addition, the five-year assessment included a sonographic assessment of the anterior aspect of the knee to identify joint effusion. RESULTS: Ninety-one patients were available for the five-year assessment (with an 89% follow-up rate). After one and five years, Baker’s cyst was still present in 87 (85%) and 30 (33%) patients, respectively. Of those patients who retained a Baker’s cyst at one-year follow up, 31 patients (36%) had sustained popliteal symptoms. Of those patients who continued to have a Baker’s cyst at five years, 17 patients (56.7%) were still symptomatic. The probability of entering remission was dependent on the size of the Baker’s cyst at baseline (odds ratio, 1.41; p = 0.025). The mean preoperative cyst size was 14.5 cm2. At one and five years postoperatively, the mean cyst size was 10.6 cm2 and 9.9 cm2, respectively. At five years, no association between cyst size and popliteal symptoms was found. CONCLUSION: Five years after TKA, the majority of the Baker’s cysts that were present at baseline had gone into remission. The probability of going into remission was dependent on the size of the Baker’s cyst at baseline.