Substantial side-to-side differences in knee cartilage contact area exist in healthy knees—Should we reconsider comparing to the contralateral side after ligament reconstruction?

Anterior cruciate ligament (ACL) rupture and subsequent surgical reconstruction (ACLR) result in altered knee kinematics, generalized knee loads, and cartilage contact patterns. 1 Li G. Moses J.M. Papannagari R. Pathare N.P. DeFrate L.E. Gill T.J. Anterior cruciate ligament deficiency alters the in vivo motion of the tibiofemoral cartilage contact points in both the anteroposterior and mediolateral directions. J Bone Joint Surg Am. 2006; 88: 1826-1834 Crossref PubMed Scopus (169) Google Scholar These biomechanical alterations can cause aberrant loading to both the reconstructed graft and knee cartilages, which may predispose individuals with ACLR knees to early-onset osteoarthritis. 2 Andriacchi T.P. Mundermann A. Smith R.L. Alexander E.J. Dyrby C.O. Koo S. A framework for the in vivo pathomechanics of osteoarthritis at the knee. Ann Biomed Eng. 2004; 32: 447-457 Crossref PubMed Scopus (784) Google Scholar It has been widely reported that native knee kinematics are not restored by ACLR and meniscal repair. 3 Andriacchi T.P. Osteoarthritis: probing knee OA as a system responding to a stimulus. Nat Rev Rheumatol. 2012; 8: 371-372 Crossref PubMed Scopus (21) Google Scholar These studies, and in fact most studies in the ACL literature, use the intact contralateral knee for comparison. 4 Pairot-de-Fontenay B. Willy R.W. Elias A.R.C. Mizner R.L. Dube M.O. Roy J.S. Running biomechanics in individuals with anterior cruciate ligament reconstruction: a systematic review. Sports Med. 2019; 49: 1411-1424 Crossref PubMed Scopus (38) Google Scholar The intact contralateral knee is assumed a good proxy for effective recovery from ACLR, despite some evidence for bilateral deficits in knee biomechanics compared with controls. 5 Pamukoff D.N. Montgomery M.M. Choe K.H. Moffit T.J. Garcia S.A. Vakula M.N. Bilateral alterations in running mechanics and quadriceps function following unilateral anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther. 2018; 48: 960-967 Crossref PubMed Scopus (36) Google Scholar