Immediate Biochemical Changes After Gait Biofeedback in Individuals With Anterior Cruciate Ligament Reconstruction

Key Points

• Among all participants with anterior cruciate ligament reconstruction, serum cartilage oligomeric matrix protein (sCOMP) did not differ between the control and the 3 experimental (symmetric, high, low) loading conditions.

• In a subgroup of participants whose sCOMP increased during the control condition, the high-loading condition resulted in decreased sCOMP. Thus, greater mechanical loading during walking may decrease the acute sCOMP response in individuals who normally demonstrate increased sCOMP after walking.

• Real-time biofeedback was useful in acutely altering joint tissue biochemistry in those with an increased acute sCOMP response to walking, which may indicate that modifying gait biomechanics is beneficial in preventing posttraumatic osteoarthritis after anterior cruciate ligament reconstruction.

Approximately one-third of individuals who sustained an anterior cruciate ligament (ACL) injury and underwent reconstruction (ACLR) developed radiographic posttraumatic osteoarthritis (PTOA) of the knee within the first decade after injury.¹ The development of PTOA is multifaceted, and previous work² supported the hypothesis that both biomechanical and biochemical changes occur after ACL injury and ACLR, and the interplay between these factors likely contributes to the early development of PTOA. Animal models demonstrated that alterations in mechanical loading, both excessive³ and insufficient,⁴ led to articular cartilage degradation consistent with the development of PTOA. In individuals with idiopathic knee osteoarthritis, excessive joint loading during gait was associated with increased serum concentrations of biochemical markers linked to cartilage breakdown⁵ and increased tibiofemoral osteoarthritis severity.⁶ Conversely, in individuals with ACLR, lesser peak vertical ground reaction force (vGRF) produced by the ACLR limb was associated with deleterious changes in cartilage metabolism that were hypothesized to contribute to PTOA development.^7,8 Therefore, increasing peak vGRF in the ACLR limb may result in more beneficial changes in joint tissue biochemistry among individuals with ACLR who are at greater risk of PTOA. Although persistent alterations in mechanical loading may influence tissue metabolism after ACLR,^7,8 whether acutely increasing or decreasing mechanical loading can influence joint tissue biochemistry in those with ACLR is unknown.

Serum cartilage oligomeric matrix protein (COMP) is a biomarker of cartilage breakdown,⁹ and resting levels of COMP are elevated in individuals with ACLR compared with healthy controls.¹⁰ The serum COMP concentration (sCOMP) is mechanosensitive and increases in a dose-dependent manner after acute bouts...