Musculoskeletal · Knee Injuries
The facts most likely to be tested
Medial Collateral Ligament (MCL) injuries typically result from a valgus stress applied to the lateral aspect of the knee.
The valgus stress test is the primary physical exam maneuver used to assess MCL integrity, performed with the knee in 30 degrees of flexion to isolate the ligament.
A positive valgus stress test is defined by increased medial joint space opening compared to the contralateral knee.
MCL sprains are frequently associated with the 'unhappy triad', which includes concurrent injury to the Anterior Cruciate Ligament (ACL) and the medial meniscus.
Grade I and II MCL sprains are managed conservatively with rest, ice, compression, elevation, and a hinged knee brace for protection.
Magnetic Resonance Imaging (MRI) is the gold standard diagnostic modality if the diagnosis is unclear or if multi-ligamentous injury is suspected.
Isolated MCL injuries have an excellent healing potential due to the ligament's robust extracapsular blood supply.
Vignette unlocked
A 22-year-old male collegiate soccer player presents to the urgent care clinic after a collision during a match. He reports that an opposing player fell onto the lateral aspect of his right knee while his foot was planted. On physical examination, there is localized tenderness along the medial joint line. The knee is stable to anterior and posterior drawer testing. A valgus stress test performed at 30 degrees of flexion reveals increased laxity and medial joint space opening compared to the left knee.
What is the most likely diagnosis and the most appropriate initial management?
Medial Collateral Ligament (MCL) sprain; conservative management with a hinged knee brace.
The patient's mechanism of injury (valgus stress) and positive valgus stress test at 30 degrees are classic for an MCL sprain, which is typically managed non-operatively.
Full handout
High yield triage
Etiology / Epidemiology
Common in contact sports involving valgus stress to the knee. Often associated with the unhappy triad.
Clinical Manifestations
Medial knee pain, swelling, and laxity with valgus stress. Valgus stress test is the diagnostic maneuver.
Diagnosis
MRI is the gold standard for grading. Clinical diagnosis via valgus stress test at 30 degrees flexion.
Treatment
Conservative management (RICE, bracing, PT) for grades I-II. Surgery reserved for grade III with instability.
Prognosis
Most return to play in 4-8 weeks. Grade III injuries require prolonged immobilization.
Full handout
Epidemiology & Etiology
Occurs frequently in athletes participating in contact sports like football or soccer. Mechanism is typically a direct blow to the lateral knee causing valgus stress. Non-contact injuries occur via sudden deceleration or pivoting.
Pertinent Anatomy
The MCL connects the medial femoral epicondyle to the medial tibial condyle. It provides primary resistance to valgus force and external rotation of the tibia.
Pathophysiology
Force applied to the lateral knee creates a tension injury on the medial structures. Grade I involves microscopic tearing, Grade II involves partial tearing, and Grade III involves complete ligamentous rupture. Often occurs alongside ACL and medial meniscus injury, known as the unhappy triad.
Clinical Manifestations
Patients report localized medial pain and swelling following trauma. Physical exam reveals laxity with valgus stress at 30 degrees of flexion. Neurovascular compromise is rare but must be ruled out by checking distal pulses.
Diagnosis
The valgus stress test is performed at 0 and 30 degrees; laxity at 30 degrees isolates the MCL. MRI is the gold standard for confirming the grade of injury and identifying associated intra-articular pathology. Radiographs are indicated to rule out avulsion fractures (e.g., Pellegrini-Stieda lesion).
Treatment
Initial management includes RICE (Rest, Ice, Compression, Elevation) and NSAIDs for pain. Grade I and II injuries are treated with a hinged knee brace and physical therapy. Avoid corticosteroid injections due to risk of ligament weakening. Grade III injuries may require surgical reconstruction if persistent instability exists.
Prognosis
Grade I and II injuries typically resolve within 4-8 weeks. Grade III injuries may require 3-6 months of rehabilitation. Monitor for chronic instability or post-traumatic osteoarthritis.
Differential Diagnosis
ACL tear: positive Lachman test
Medial meniscus tear: McMurray test and joint line tenderness
LCL injury: laxity with varus stress
Tibial plateau fracture: pain on weight-bearing and bony tenderness
Pes anserine bursitis: localized tenderness distal to the joint line