Differentials
Medial meniscus tear
SIGNS / SYMPTOMS
Patients frequently complain of mechanical symptoms in their knees such as catching, giving way, locking, clicking, and popping; these symptoms are unusual in isolated MCL injuries.
May present with quadriceps atrophy and often have an associated knee effusion and tenderness localized to the joint line. In contrast, MCL injuries have tenderness above and below the joint line following the path of the MCL. The McMurray test can be used for diagnosing meniscal injury. It is performed with the patient lying supine and the examiner placing one hand on the lateral joint line, providing a valgus stress. If pain or a click is felt as the knee is externally rotated and brought into full extension, the exam is positive, and suggestive of a medial meniscal tear. The McMurray test has a low positive predictive value (82.6%) and therefore has a limited role in clinical practice.[28]
INVESTIGATIONS
MRI is the most accurate test. MRI reports score the quality of the meniscus signal on a 0-III scale: grade 0 represents normal, healthy meniscus and grade III represents a torn meniscus.
Diagnostic ultrasound of the knee may also be useful in visualizing pathology.
Soft tissue contusion of the medial knee
SIGNS / SYMPTOMS
Patients usually describe an object impacting the knee.
Absence of valgus laxity on abduction stress testing.
INVESTIGATIONS
MRI or ultrasound will show edema surrounding the contusion but should demonstrate an intact MCL with normal-appearing fibers.
Tibial plateau fracture
SIGNS / SYMPTOMS
Usually involves a large force on the knee, commonly seen in major falls or motor vehicle accidents.
Significant pain, effusion, and joint stiffness are typical symptoms.
INVESTIGATIONS
Plain x-rays in multiple orientations (anteroposterior, lateral, patellofemoral, and oblique) will usually reveal a disruption of the tibial articular surface.
CT provides a more detailed view of the pathology.
Osteochondral fracture
SIGNS / SYMPTOMS
Immediate pain and swelling of the knee at the time of injury. Significant pain with weight-bearing.
Mechanism of injury usually involves a high-force, twisting injury of the knee.
INVESTIGATIONS
Osteochondral fractures may be missed on x-rays. CT and MRI are preferred as they provide more detailed images.
Pes anserinus bursitis
SIGNS / SYMPTOMS
Tenderness along the medial knee, exacerbated by ascending and descending stairs. Pain is usually absent when walking on a level surface.
Unlike MCL sprains, there is usually no history of acute injury.
Tenderness at the conjoint tendons of the pes anserinus, located 3 to 5 cm below the anteromedial margin of the knee.
No valgus laxity on abduction stress testing.
INVESTIGATIONS
T2-weighted MRI images demonstrate an increase in signal intensity in the pes anserinus bursa.
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