ACL Injury Reconstruction


The harsh reality for individuals who sustain an anterior cruciate ligament (ACL) rupture is that their risk of developing knee osteoarthritis (OA) increases substantially (1). Although quadriceps weakness is a risk factor for developing OA,

the relationship between other functional performance tasks and early onset of OA is unknown (2).

The primary objective of this study was to determine if functional performance 1 year following ACL reconstruction (ACLR) was associated with 1) the risk of patellofemoral and/or tibiofemoral OA on MRI, and 2) changes in patient-reported outcomes between 1 and

5 years.


Individuals who underwent a single-bundle hamstring autograft ACLR were assessed 1 and 5 years after surgery. Participants completed a

Improving functional deficits during rehabilitation
may benefit both return
to sport aspirations and simultaneously delay or prevent the development of osteoarthritis.

battery of functional tests including single-leg hop (cm), crossover hop (cm), single-leg side hop (max reps in 30 seconds), and one-leg rise (max reps). Limb symmetry index (LSI) was calculated for each test. See the video for a demonstration of these tests.

One outcome of interest was worsening OA defined as an increase in size or severity of an OA feature, or new OA feature on MRI from 1 to 5-year testing. The other outcome of interest was change in score on the Knee injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee Subjective Form (IKDC) from 1 to 5-year testing.

Regression models were used to determine
the association between worsening OA and change in KOOS and IKDC scores with functional performance at 1-year post-ACLR. These analyses

accounted for the presence of a combined injury (i.e. significant cartilage defect and/or meniscus resection/repair), age at 1-year post- ACLR, sex, height, weight, and baseline KOOS and IKDC scores.

The risk of developing knee osteoarthritis increases substantially after ACL rupture.


A total of 111 participants (64% male) with
a median age of 27 years (range 19-51) were assessed at 1-year post-ACLR. The majority (69%) reported playing in jumping, cutting, and pivoting sports pre-injury, and approximately half (49%) had a combined injury. At the 1-year mark, only
1 in 5 participants (18%) successfully achieved >90% LSI on all four functional tests.

At the 5-year follow-up, 78 had an MRI scan and 81 completed their patient-reported outcome measures. The prevalence of OA grew from
6% of participants at 1 year to 19% at 5 years post-ACLR. Worsening cartilage was the most common change of the OA features examined. Specifically, patellofemoral and tibiofemoral cartilage worsening was found in 44% and 21% of participants at 5 years, respectively. For patient- reported outcomes, all KOOS subscale and IKDC scores (except for KOOS symptoms) significantly improved at the 5-year mark.

Participants who demonstrated poor functional performance (i.e. did not achieve >90% LSI on any test) had 3.66 times the risk of worsening patellofemoral bone marrow lesions compared to those who passed at least one functional
test. Generally, participants who did not meet the 90% LSI cut off for any one of the functional tests had an increased risk of worsening patellofemoral cartilage or bone marrow lesions. In contrast, functional performance at 1-year post-ACLR was not associated with changes in KOOS or IKDC scores.


The authors acknowledged that this study may have been underpowered for the statistical analyses that were performed. Additionally, other factors that should be considered in future OA risk prediction models include (but are not limited to) movement patterns, physical activity

ACL Functional Testing battery

levels, time from injury to ACLR, adiposity,
pain, kinesiophobia, knee confidence, and healthcare utilization. It is also important to note that radiographic or MRI-defined OA does not necessarily equate with symptomatic OA. Lastly, using LSI as an outcome of functional performance may overestimate function given the bilateral neuromuscular deficits that follow ACLR (3).


Not meeting the 90% LSI cut-off on any of the functional performance tests at 1-year post-ACLR was generally linked with an increased risk of having worsening patellofemoral OA features

at the 5-year mark. Although the development of OA is multifactorial, existing neuromuscular deficits may impact how individuals load their knee following ACLR. Considering these cut-offs are typical of
return to sport criteria as well, it is possible
that improving functional deficits during rehabilitation may benefit both return to sport aspirations and simultaneously delay or prevent the development of OA. A more comprehensive set of functional tests (e.g. strength, endurance, change of direction) and patient-reported outcomes (e.g. readiness to return to sport, kinesiophobia, knee confidence) may help predict long-term clinical outcomes.

Clinicians should also educate patients about their increased risk of developing OA following an ACL injury or ACLR. If patients understand that achieving high standards of physical function
can improve their odds of a successful return
to sport, and minimize their risk of developing OA, there may be better buy-in for adhering


  1. Poulsen E, Goncalves GH, Bricca A, et al. Knee osteoarthritis risk is increased 4-6 fold after knee injury – a systematic review and meta-analysis. Br J Sports Med. 2019;53:1454-63.
  2. Øiestad BE, Juhl CB, Eitzen I, et al. Knee extensor muscle weakness is a risk factor 38 for development of knee osteoarthritis. A systematic review and meta-analysis. Osteoarthritis Cartilage 2015;23:171-7.
  3. Wellsandt E, Failla MJ, Snyder-Mackler L. Limb symmetry indexes can overestimate knee function after anterior cruciate ligament injury. J Orthop Sports Phys Ther 2017;47:334-8.

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