Unfortunately I see that many of my Danish colleagues still do an 'open' surgical Baker's cyst removal as opposed to a keyhole (arthroscopic) procedure.

A Baker's cyst (or popliteal cyst) is a fluid-filled swelling at the back of the knee. If you are troubled by such a cyst there is a high chance (about 90%) that it is the result of a previous knee injury such as a meniscal tear, cartilage lesion or an ACL rupture.

 

Fluid retained via a 'valve' action

The reason a Baker's cyst can occur is a fold (or plica) of the lubricating joint lining at the rear of the joint cavity that produces fluid which would be normal except that sometimes the fold acts as a valve - so that the fluid circulating at the back of the knee cavity runs into the cyst, but it cannot escape. If the cyst does not resolve by the method of manually emptying it and injecting steroid, then you need to have the cyst removed. For this you need to have a special arthroscopic procedure with removal of the plica at the rear of the knee.

If you are one of those people in whom a Baker's cyst has formed without the sort of injury mentioned above, don't let anyone remove your cyst via an 'open' technique from the back of the knee, since there is a 60% risk of relapse. 

 

My preferred surgical technique

My own preferred method is to deal with the problem arthroscopically, passing the keyhole surgery instruments into the back of the knee, locating the valve-like entrance into the cyst from within the knee cavity, and then trimming away the valve edges to allow the pressure in the cyst to equalise with that inside the knee All the cyst fluid should then simply drain back into the knee joint cavity and the swelling collapses.

I also think it is important to mention that it is not the standard 'open-versus-arthroscopic' discussion that is at issue, but really we are talking about a completely different procedure. The surgeon cannot reach the valve (plica) by an open method from the back of the knee - you can only reach it from the front, by an arthroscopic method in the region of the knee we call the posterior compartment. I find it strange that despite my attendance at many international symposia, congresses and courses, I hear no one focusing on this topic. I guess the issue is not confined to Denmark?

 


References

1. Ahn JH, Yoo JC, Lee SH, Lee YS. Arthroscopic cystectomy for popliteal cysts through the posteromedial cystic portal. Arthroscopy. 2007 May;23(5):559.e1-4. Epub 2007 Jan 5.

2. Cho JH. Clinical Results of Direct Arthroscopic Excision of Popliteal Cyst Using a Posteromedial Portal. Knee Surg Relat Res. 2012 Dec;24(4):235-40. doi: 10.5792/ksrr.2012.24.4.235. Epub 2012 Nov 29. [ Free full text with imaging ]

3. Pankaj A, Chahar D, Pathrot D. Arthroscopic management of popliteal cysts. Indian J Orthop. 2016 Mar-Apr;50(2):154-8. doi: 10.4103/0019-5413.177568. [ Free full text  with imaging ]

4. Zhou XN, Li B, Wang JS, Bai LH. Surgical treatment of popliteal cyst: a systematic review and meta-analysis. J Orthop Surg Res. 2016 Feb 15;11:22. doi: 10.1186/s13018-016-0356-3. [ Free full text ]

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