2015 ISAKOS Biennial Congress ePoster #1242

Single-Legged Hop Scores Early After ACL Injury Associated With Knee OA 5 Years Later

Elizabeth Wellsandt, DPT, PhD, Omaha, NE UNITED STATES
Kurt Manal, PhD, Newark, DE UNITED STATES
Michael J. Axe, MD, Newark, DE UNITED STATES
Thomas S. Buchanan, PhD, Newark, DE UNITED STATES
Lynn Snyder-Mackler, PT, ScD, FAPTA, Newark, DE UNITED STATES

University of Delaware, Newark, DE, USA

FDA Status Not Applicable

Summary: Athletes who develop early onset radiographic knee osteoarthritis (OA) 5 years after anterior cruciate ligament (ACL) injury demonstrate significantly lower single-legged hop scores early after injury than those without radiographic knee OA.




The risk of knee osteoarthritis (OA) significantly increases following anterior cruciate ligament (ACL) injury. However, little is known regarding potential risk factors exhibited early after injury that may increase the risk of OA. Identification of such risk factors may present modifiable pathways to alter the course of joint degeneration. Therefore, the purpose of this study was to determine whether clinical differences exist early after ACL injury between those who do and do not develop radiographic knee OA 5 years later.


Forty-six athletes (16 F, mean age 30.3±11.7 years) with acute, unilateral ACL injury were included. Exclusion criteria included repairable meniscus injury, symptomatic grade III injury to other knee ligaments, and articular cartilage lesions >1 cm2. Patients completed testing when impairments of pain, range of motion, effusion, and obvious gait dysfunction were resolved initially after injury. Testing consisted of burst superimposition quadriceps strength testing, single-legged hop tests (single, crossover, triple, and timed), and patient-reported outcomes including the Knee Outcome Survey Activities of Daily Living Scale (KOS), Global Rating Scale of Perceived Function (GRS), and International Knee Documentation Form 2000 (IKDC 2000). Quadriceps strength and hop scores were calculated using symmetry indexes. Crossover and triple hop data was only available for 26 patients.
Seven patients completed non-operative management while 39 underwent ACL reconstruction (ACLR) using either a hamstring allograft or soft tissue allograft. Five years after ACL injury (non-operative) or ACLR patients completed the Marx Activity Rating Scale (Marx) and posterior-anterior 30° bent knee radiographs. Radiographs were graded using the Kellgren-Lawrence grading system with a grade 2 or greater operationally defining OA (OA, nonOA).
Independent t-tests and Fisher’s exact tests were used to test differences in demographics, strength and hop measures, and patient-reported outcomes between those who did and did not have OA at 5 years.


At 5 years 10 patients had OA, 36 did not. No group differences existed in age (p=0.569), sex (p=0.455), BMI (p=0.926), days from injury to baseline testing (p=0.590), or proportion of patients who chose operative versus non-operative management of injury (p=0.319). Patients with OA had significantly lower single hop (p=0.031; OA: 77.5±21.0; nonOA: 90.2±14.3) and triple hop (p=0.032; OA: 74.9±17.2; nonOA: 89.4±11.5) scores than those without OA. They also hopped worse during the crossover hop (p=0.377; OA: 80.8±16.6; nonOA: 90.1±21.4) and timed hop (p=0.366; OA: 87.5±18.4; nonOA: 94.0±19.0) although not statistically significant. No group differences were present in quadriceps strength (p=0.351), KOS (p=0.551), GRS (0.185), IKDC (0.659), or 5-year Marx scores (0.356).


of this study suggest those who develop early radiographic OA have poorer ability to hop on the involved limb initially after injury than those who do not. Lower joint loading early after injury has been associated with later knee OA, and lower single-legged hop scores may reflect these altered loading patterns. Hop tests may provide a measure simple to complete in a clinical setting sensitive to increased risk of early onset OA. Further work is warranted to investigate whether altered single-legged hopping is associated with lower knee joint loads.