I had a new-fangled surgery called allograft meniscus transplantation. I’m three years out and doing great — back to full work schedule, able to hop, skip, and jump, and even get out on the golf course a bit. At my final check up yesterday, the surgeon showed me on the MRI how the graft is pushing out of the joint. I don’t have any pain or other symptoms so there’s no apparent concern. But I’m doing a little Internet research of my own to find out if this could be a problem. What can you tell me?

Allograft meniscus transplantation refers to the use of donor cartilage to replace what was removed from your knee. Since we don’t have any extra meniscus material anywhere else in the body to use, surgeons must rely on a donor bank for the graft material.

We’ve known for quite some time now that removing the meniscus leads to early degenerative arthritis of the knee. So whenever possible, the meniscus is preserved and stitched back in place to restore the natural anatomical structure of the knee. But sometimes it isn’t possible to save the meniscus. When it is removed, this type of transplantation is possible.

Surgeons are trying different surgical techniques and reporting on their results. They are looking for the least invasive, most successful approach that gives patients pain relief and improved knee function. The goal is to allow them to do exactly what you describe — whatever they want to whether that’s hopping, skipping, or chasing after a ball on the fairway.

A review of many studies shows a fairly high rate of what you are experiencing: extrusion of the graft. Extrusion of the graft refers to pushing of a part of the graft material out of the knee joint cavity. This extrusion was more common in grafts on the lateral side of the knee (the side away from the other knee). There does not appear to be any effect of this extrusion on pain or function — at least not in the short-term. Long-term studies may show a different result.

No one knows exactly why graft extrusion occurs. But it is commonly reported in all studies involving meniscal transplantations. Experts suggest a variety of possible reasons for this problem. The fact that the lateral side pushes out more often than the medial side (side closest to the other knee) suggests factors involving biomechanics and load distribution.

But it could be there are effects of surgical technique from putting too much tension on the sutures, using a graft that’s too large for the space (called “overstuffing”), or when the sutures do not reattach the graft at the anatomical location (where the meniscus normally inserts into the bone).

Since patients are usually asymptomatic (without symptoms), the usual approach is to wait-and-see what happens. Surgeons sometimes refer to this as “benign neglect.” In other words, they keep an eye on it and intervene only if it causes a problem. If you start to experience any unusual pain or symptoms anytime in the future, don’t hesitate to get back to your surgeon for a follow-up appointment. Until then, we hope you continue to enjoy the benefits this surgery has provided you with!