Front Knee Pain After ACL Surgery?

ACL marked 20mm from each end by Dr Nuelle

While looking for a topic to write this week, I came across a research paper by Rahardja et al (2023) comparing knee pain and difficulty with kneeling between the bone-patella tendon bone (BTB) and hamstring graft after anterior cruciate ligament (ACL) reconstruction. 

I subsequently found a Twitter thread concerning the article where an orthopaedic surgeon says he "don't believe" what the paper says (see picture below).

Compared to now, there were more patients whose surgeons used the BTB graft when they tore their ACL's when I started work as a physiotherapist in the late 1990's. The hamstring autograft (not cadaver graft) is most commonly used now. 

One of the main reasons patients are told not to use a BTB graft  is because it (supposedly) causes anterior (or front) knee pain. 

A total of 10,999 patients who had ACL reconstructions were analyzed at 2-year follow-up. 9.3 percent (420 cases out of 4492 reported consequential knee pain (CKP) while 12 percent (537/4471) reported severe kneeling difficulty (SKP). For those into research, the Knee and Osteosrthritis Outcome Score (KOOS) was used to identify patients reporting CKP, defined as a KOOS Pain subscore of ≤ 72 points. 

The authors wrote that the most important predictor of CKP at 2-year follow-up was having significant pain before surgery while the most important predictor of SKP was the use of a BTB versus hamstring graft.

I do not agree with the authors' observation. I have treated many patients who had ACL reconstructions in the past 24 years. In the first few weeks after the ACL reconstruction, patients who choose either graft do have a little anterior knee pain presumably from the operation itself. After 6 weeks, anterior knee pain is very rare especially for those with the BTB graft. Very occasionally if they kneel onto the BTB graft site, they may have some kneeling pain which goes away quickly once they change position.

In fact, an orthopaedic surgeon commented that his few "non BTB" (i.e. hamstring graft) patients tend to have more anterior knee pain than his BTB graft patients (see picture below).

Moreover if you have read my earlier post, Spindler et al (2020) suggests that the HS graft is 2.1 times more likely to tear again compared to the BTB graft. Surely this is supporting evidence that the BTB graft is the 'better' and 'stronger' graft? 

There should be no reason to use "anterior knee pain" as an 'excuse' to use other graft choices rather than the BTB graft. 

Choosing your graft after tearing your ACL will definitely be influenced by discussions with your doctor, surgeon and physiotherapist. If you do not want to use your own BTB and hamstring graft, you can also use an allograft (cadaver) now. 

Please keep this information in mind if you were to tear your ACL. Come talk to us if you have any questions.

References

Rahardja R, Love H, Clatworthy MG et al (2023). Comparison Of Knee Pain And Difficulty With Kneeling Between Patella Tendon And Hamstring Tendon Autografts After Anterior Cruciate Ligament Reconstruction: A Study From the New Zealand ACL Registry. AJSM. DOI: 10.1177/03635465231198063

Spindler KP, Huston LJ, Zajichek A et al (2020). Anterior Cruciate Ligament Reconstruction In High School And College-age Athletes: Does Autograft Choice Influence Anterior Cruciate Ligament Revision Rates? 48(2): 298-309. DOI: 10.1177/0363546519892991.

Which ACL Graft is Less Likely To Tear Again?

Post op -view from the front

In all my years of being a physiotherapist, I have treated many patients and athletes who tore their anterior cruciate ligament (ACL) and opted to have surgery to repair it. 

View from the back

In the earlier days, the bone patella tendon bone (BTB) graft and the hamstring/ gracilis (HS) graft were the more popular choices. Allografts (cadaver graft) were not popular then, but they are definitely more accepted now.

I've had many patients (not just the athletes) who subsequently re-tore their HS graft. However, I have yet to encounter a patient who re-tore their BTB graft.

If my observations were accurate, surely then the BTB graft would be the 'better' and 'stronger' graft? Now it seems like there is evidence supporting my observations.

Researchers studied 770 patients (14-22 years) who were injured playing sports and had a six year follow up period. These patients had one normal un-injured knee and the injuredACL knee was reconstructed using the BTB or HS graft. Average age of the subjects was 17 years, of which 48% were female.

There were 492 (64%) BTB grafts and 278 (36%) HS grafts.

The chance of a subsequent  tear on the same reconstructed knee at six years was 9.2% compared to 11.2% in the uninjured normal knee. If it was either knee, the rate goes up to 19.7%.

The three most likely predictors of a subsequent re tearing of the operated knee were knee ligament laxity prior to knee operation, graft selection and age.

Those patients who had a HS graft were 2.1 times more likely to re-tear their ACL graft compared to those who had the BTB graft.

Choosing your graft after tearing your ACL will definitely be influenced by discussions with your doctor, surgeon and physiotherapist etc. Moreover, besides the BTB and HS grafts, you can also use an allograft (cadaver) now. 

Please bear this information in mind if you were to tear your ACL. Please come talk to us if you have any questions.

Reference

Spindler KP, Huston LJ, Zajichek A et al (2020). Anterior Cruciate Ligament Reconstruction In High School And College-age Athletes: Does Autograft Choice Influence Anterior Cruciate Ligament Revision Rates? 48(2): 298-309. DOI: 10.1177/0363546519892991.

R knee