Q: Is it true that people who have a patellar graft for a destroyed ACL will get worse arthritis than if we had gotten the hamstring graft? I know it's too late now that I went the patellar graft route, but I still wonder (especially on days the knee feels arthritic).

A: Long-term studies do show that a knee with an anterior cruciate ligament (ACL) repair or reconstruction is at risk for early arthritis. In fact, studies show patients with an ACL rupture (rupture means torn completely through) eventually develop knee osteoarthritis (OA) a full 15 years sooner than adults the same age without this type of knee injury.

Surgery to reconstruct a ruptured ACL is usually done to spare the knee joint further damage. Without an intact ACL, the tibia (lower leg bone) slides forward under the femur (thigh bone). This excess joint motion can cause wear and tear that a stable joint would not be subjected to.

Many times, a force strong enough to cause a complete rupture of the ACL is enough to damage other soft tissues in the knee such as the joint cartilage or the meniscus. Without these additional protective structures, the joint is at increased risk for degenerative changes leading to arthritis. Preventing this early development of osteoarthritis (OA) is another reason surgeons recommend surgery when the ACL is ruptured.

Surgeons do consider whether the surgery itself may be a risk factor for later osteoarthritis (OA). And beyond that -- whether the type of surgery performed is a risk factor for OA. The two major types of ACL reconstruction involve taking a piece of donor graft tissue from some other area of the same patient's knee and using it to replace the torn ligament. The two most common donor sites are the hamstring tendon (behind the knee) and the patellar tendon from the front of the knee.

In a recent study from the Australian Institute of Musculoskeletal Research, degenerative changes in the knee after ACL reconstructive surgery were investigated. The researchers limited their research to patients who had a bone-patellar tendon-bone (BPB) autograft. As you know from your own procedure, autograft refers to the fact that the donor tissue is the patient's own graft material.

The results of previous studies have indicated that osteoarthritis may occur more often after bone-patellar tendon-bone (BTB) grafting. The authors questioned this finding and suggest there are other risk factors potentially associated with poor outcomes following BTB reconstruction.

To explore this idea further, they followed 114 of their own patients who had the BTB procedure. Follow-up was considered long-term with an average time of 13 years. X-rays were used to identify and rate severity of arthritic degenerative changes throughout the follow-up period. Whenever possible, X-rays of the uninvolved knee were used as the control group since that leg had not been subjected to surgery.

Tests of knee motion, strength, and function were also used to assess changes over time. They found that one-third of the group developed abnormal to severely abnormal arthritis changes. This rate of 33 per cent was higher than the 12.8 per cent rate of knee osteoarthritis in the general population. In other words, the injured knee was significantly more likely to show signs of osteoarthritis compared with the nonoperative side.

After analyzing all the data, there were several risk factors identified for osteoarthritis after BTB grafting. These included: 1) injury to the first layer of bone under the articular cartilage of the knee joint (chondral bone), 2) a previous knee surgery, and 3) not returning to sports. Previous knee surgeries reported in this group included arthroscopic exam, meniscus cartilage repair or removal, and/or removal of a bone tumor.

The authors concluded that there is indeed a higher rate of degenerative joint changes after bone-patellar tendon-bone (BTB) grafting for rupture of the anterior cruciate ligament (ACL). Whether or not a different reconstructive technique would have the same effect was not determined in this study. But a number of other risk factors may be the real key to the early development of arthritis observed in this patient group.

The most significant contributing risk factor seems to be the presence of chondral damage at the time of the initial injury. This association may be explained by microscopic damage to bone cells. This damage is made worse when surgery is delayed and the patients continue to walk on that leg with a change in normal knee joint biomechanics. Meniscus damage also contributes to changes in the load bearing on the joint leading to osteoarthritis. The use of a bone-patellar tendon-bone graft may not be the main predictor of early degenerative bone disease.

Reference: James R. D. Murray, MB BChir, MA, FRCS (Tr & Orth), et al. Does Anterior Cruciate Ligament Reconstruction Lead to Degenerative Disease? In The American Journal of Sports Medicine. February 2012. Vol. 40. No. 2. Pp. 404-413.