1. INTRODUCTION Current literature reports 2,000,000 anterior cruciate ligament (ACL) injuries worldwide, with children and adolescents accounting for 0.5%-3% of the injuries in the United States. Isolated ACL injuries occur less than 50% of the time and are divided into contact and noncontact injuries. Limited evidence exists on the management of ACL injuries in children younger than 10 years old. While surgical management often leads to increased knee stability, potential growth plate damage from surgical intervention can be detrimental to the long-term functional capacity of the child. ANATOMY/BIOMECHANICS OF THE ACL One of four major ligaments supporting the knee Intra-articular, extrasynovial, and well vascularized Prevents anterior tibial translation in open chain motion Maximally stressed during the last 30° of knee extension Limits sagittal, frontal, and transverse plane motions HISTORY/EXAMINATION MOI: landed from jump with the left knee in a position of flexion, internal rotation, and valgus Unable to weight-bear symmetrically secondary to pain Went to the ED findings revealed a 3+ Lachman test and an a midsubstance ACL tear confirmed by MRI. PSH: right congenital club foot had Achilles tendon lengthening (2008), posterior medial capsule release (2011) NPRS 4/10 Effusion: 1+ (stroke test) Joint mobility: hypomobility TFJ and PFJ Special tests: 1+ Lachman test, +Thomas test Gait: decreased left terminal knee extension Stair negotiation: unreciprocal with right LE leading SLS: left 5 seconds; right 5 seconds Dynamometer quad strength: 70% KOOS 58/100 MOTIONAROM°PROM°MMT RightLeft RightLeftRight Hip flexion120 3+/55/5 Hip ER502535503/5 Hip AB40 3/54-/5 Knee flexion14590 1504-/55/5 Knee extension00015-03+/55/5 Ankle DF0152055/5 Ankle PF50 3/52/5 Treatment PhaseGoals of PhaseInterventions Phase 1 (Week 1-4)Decrease pain 4/10 – 0/10 Decrease effusion to trace Obtain symmetrical ROM Independent HEP Retrograde massage Patella mobilization Soft tissue stretching HEP – quad sets, bridging, SLR Phase II (Week 5-8)Increase MMT by 1 grade SLS ≥ 30s Promote TKE during gait Therex: step up/down, clam shells, squats Retro treadmill walking SLS with ball catch Phase III (Week 9- 12) Dynamometer quad strength > 85% SLS ≥ 60s KOOS > 80/100 Therex: step up/down, squats Functional drills: running weaving, cutting through cones, hopping, jumping Measure (Left)Baseline (IE)Re-eval (2 mo) Discharge3 Mo. Follow-Up KOOS (0-100)58759070 NPRS (0-10)4000 Dynamometer (quad strength) 70%75%85%73% AROM°0-9015-0-150 0-146 Hip AB MMT3/54-/54+/53+/5 Hip ER MMT3/54-/54+/55/5 Hip Flex MMT3+/54-/54+/5 DF MMT5/5 PF MMT3+/54/55/54+/5 SLS56090120 OUTCOMES INITIAL ROM AND MMT DISCUSSION We suggest children are capable of performing structured programs that initially aid in the restoration of quadriceps strength and neuromuscular control following an ACL tear We do recognize however, that the pediatric population may require less structured exercises to maintain compliance We also recognize that this injury could have had a positive outcome due to spontaneous healing of the ACL in such a young child Despite successful short-term outcomes, we cannot predict whether functional loss or other structural damage will occur in the future CONCLUSION This case report described the successful conservative management of a five year-old child presenting with a mid-substance ACL tear. Clinicians are encouraged to consider all variables present when choosing optimal interventions during management of ACL injuries in the skeletally immature patients. We suggest a combination of quadriceps strengthening, playful activities, and neuromuscular control drills to optimize strength and motor control before a full return to unrestricted activity.