Five-year follow-up of knee joint cartilage thickness changes after acute anterior cruciate ligament rupture.
Eckstein F, Wirth W, Lohmander LS, Hudelmaier MI, and Frobell RB. Arthritis Rheum. [Epub Ahead of Print].
Take Home Message: Following an anterior cruciate ligament (ACL) rupture overall cartilage thickness in the tibiofemoral joint increased at an average of 0.4% per year. Patients under 25 years of age showed greater cartilage thickening than older patients.
In addition to immediate physical limitations, a patient who experiences an ACL rupture also has an increased risk of long-term disability due to structural adaptations within the joint. If clinicians could identify early changes in the joint then clinicians may eventually be able to implement pharmacological and rehabilitation protocols to limit joint cartilage changes and other structural changes that may lead to osteoarthritis. Therefore, Eckstein and college completed a prospective study to quantify tibiofemoral cartilage thickness changes in patients with an ACL rupture. The researchers assessed 121 physically-active individuals (18-35 years old, 89 men) with ACL ruptures who participated in the KANON randomized control trial. Sixty-two participants underwent rehabilitation and early ACL reconstruction (within 10 weeks of injury) and 59 participants received rehabilitation with the option of a delayed ACL reconstruction. Sixty participants sustained meniscal injuries in addition to the ACL rupture. The researchers measured joint cartilage thickness changes by magnetic resonance images at baseline (4 weeks post injury), 2 year post-injury, and 5 year post-injury. Overall, joint cartilage thickness increased (0.4% increase per year) in the 5 year-follow period. Participants younger than 25.3 years of age had greater annual cartilage thickness increases compared with older participants. Cartilage thickening was most significant in the medial tibiofemoral compartment while cartilage thinning was noted in the posterior region of both the medial and lateral tibia. There was some evidence to suggest that changes in joint cartilage thickness may be more greater in some areas of the knee during the first 2 years after an injury compared with years 3-5 post injury.
While these findings may not impact our current day-to-day clinical practice the data suggests that we can detect changes in the cartilage of the tibiofemoral joint during the first 5 years after an ACL rupture. This complements other work from the KANON trial that showed that changes in bone shape occur over the first 5 years after an injury. While the joint cartilage overall increased in thickness there were also areas with cartilage thinning. The areas of thickening may represent an attempt to adapt to biomechanical changes caused by the ACL rupture or swelling of the cartilage. These findings may suggest that changes in the joint biomechanics may be leading to different tibiofemoral contact points. The researchers also noted that the areas most affected may vary between participants – it would be interesting to learn if treatment influenced which regions were most affected. This study should serve as a reminder to clinicians that joint injuries can have long lasting effects, like osteoarthritis, that will cause chronic pain and disability. Traditionally, osteoarthritis wasn’t diagnosed until years after the patient left our care but with newer imaging approaches we can see that the changes begin while they are still under our care. As a community focused on injury and illness prevention we need to do everything we can to prevent these chronic conditions among our patients. This may include promoting injury prevention programs, education patients about the risk for osteoarthritis, and trying to optimize joint health after an injury.
Questions for Discussion: How much does the long-term health of the knee affect your clinical decision making in your current setting? Do you talk to your patients about the risk of osteoarthritis after a joint injury? Do you think early detection of change in joint health after an injury will change clinical practice?
Written by: Kyle Harris
Reviewed by: Jeffrey Driban