Figure: Coronal magnetic resonance imaging of the right knee.
A 22-year-old woman presents to the office with severe right knee pain. She notes that she was struck in the knee by her sprinting dog. Since the injury, she is having severe pain when weight-bearing on the right leg. On physical examination, she has a large right knee effusion and significant laxity of the medial collateral ligament (MCL) at 20 degrees and at 0 degrees. She has a negative Lachman test of the anterior cruciate ligament and a negative posterior drawer test of the posterior cruciate ligament. She has severe tenderness to palpation along the medial tibial plateau at the insertion area of the MCL. Initial radiographs taken in the office are normal. A coronal magnetic resonance imaging (MRI) shows a 2-mm depressed lateral tibial plateau fracture with a complete rupture of the distal MCL off the tibia (Figure).
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The medial collateral ligament (MCL) is the most commonly injured ligament in the knee. The mechanism of injury is generally an impact to the lateral knee that causes valgus stress to the knee. Isolated grade I and II MCL injuries are the most common types that can be treated nonoperatively.1 Grade III injuries (the most severe type) occur with other concomitant knee injuries in 80% of cases, most commonly ACL injuries followed by meniscus tears and plateau fractures.1
Generally, isolated grade III MCL injuries can be treated nonoperatively; however, the location of the tear plays a crucial role in predicting healing. An MRI is crucial in determining the location of the tear and should be performed for all grade III MCL tears.1,2 A careful physical examination can locate the site of the MCL tear with point of maximal tenderness to palpation being proximal on the femur, midsubstance, or distal on the tibia.
Complete distal MCL tears off the tibial side tend to not heal with nonoperative treatment, particularly in the athletic population. Distal MCL injuries can cause entrapment of the ligament in the medial joint space or displacement over the pes anserinus tendons (Stener-like lesion). For this reason, acute MCL injuries in athletes with complete disruption at the tibial side should be treated with surgical repair within 7 to 10 days of injury.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopaedics for Physician Assistants.
1. Miyamoto RG, Bosco JA, Sherman OH. Treatment of medial collateral ligament injuries. J Am Acad Orthop Surg. 2009;17(3):152-161. doi:10.5435/00124635-200903000-00004
2. Wilson TC, Satterfield WH, Johnson DL. Medial collateral ligament “tibial” injuries: indication for acute repair. Orthopedics. 2004;27(4):389-393. doi:10.3928/0147-7447-20040401-15