# Clinical Cases: Lower Limb - Leg and Knee ## Case 1: Anterior Cruciate Ligament (ACL) Tear ### Clinical Image ![ACL Tear MRI](case_01_image.jpg) *Source: [Wikimedia Commons - ACL Tear MRI](https://commons.wikimedia.org/wiki/File:ACL_tear_MRI.jpg) - CC BY-SA 3.0* ### Case Presentation A 22-year-old female soccer player presents to the emergency department after injuring her left knee during a game. She was planting her left foot to change direction when she felt her knee "give way." She heard and felt a "pop" at the time of injury and fell to the ground unable to continue playing. She reports immediate swelling of the knee within 2 hours. Physical examination reveals a tense effusion of the left knee. Range of motion is limited by pain and swelling (10-90 degrees vs. full on the right). Lachman test is positive with increased anterior tibial translation and soft endpoint compared to the right knee. Anterior drawer test is also positive. Pivot shift test reproduces her sensation of instability. There is no varus or valgus instability. McMurray test is equivocal. Radiographs show no fracture but a joint effusion. MRI confirms a complete midsubstance ACL tear with bone bruising in the lateral femoral condyle and posterolateral tibial plateau (typical pivot shift pattern). There is also a lateral meniscus posterior horn tear. After discussion of treatment options, she elects for ACL reconstruction with patellar tendon autograft to return to competitive sports. ### Key Learning Points - The ACL prevents anterior translation of the tibia and provides rotational stability - ACL injuries commonly occur with non-contact pivoting, cutting, or landing with knee near extension - Females have 2-8 times higher ACL injury rates due to anatomic, hormonal, and neuromuscular factors - Acute hemarthrosis after knee injury is ACL tear until proven otherwise (70% have ACL injury) - Lachman test is more sensitive than anterior drawer; pivot shift indicates functional instability --- ## Case 2: Acute Compartment Syndrome of the Leg ### Clinical Image ![Compartment Syndrome](case_02_image.jpg) *Source: [Wikimedia Commons - Compartment Syndrome](https://commons.wikimedia.org/wiki/File:Compartment_syndrome.jpg) - CC BY-SA 3.0* ### Case Presentation A 19-year-old man is admitted following closed reduction and casting of a right tibial shaft fracture sustained during a motorcycle accident. Eight hours after injury, he reports worsening pain in his right leg that is not controlled with IV morphine. He describes the pain as severe, constant, and burning, located throughout his lower leg. The nursing staff notes increasing analgesic requirements. Physical examination reveals a tense, swollen right leg. Pain is dramatically increased with passive extension of the toes (stretch of flexors in deep posterior compartment) and passive toe flexion (stretch of extensors in anterior compartment). The cast has been bivalved. Sensation is diminished over the first web space (deep peroneal nerve). Dorsalis pedis pulse is palpable. Intracompartmental pressure measurements reveal elevated pressures in all four compartments: anterior (55 mmHg), lateral (45 mmHg), deep posterior (52 mmHg), and superficial posterior (42 mmHg). Diastolic blood pressure is 80 mmHg, giving a delta pressure of 25-38 mmHg (abnormal <30). He is taken emergently to the operating room for four-compartment fasciotomy. At surgery, the muscles appear dusky but pink up after release. The fascia is left open and the wounds closed with skin grafting 5 days later. ### Key Learning Points - The leg has four compartments: anterior, lateral, superficial posterior, and deep posterior - Compartment syndrome occurs when increased pressure compromises perfusion and tissue viability - Pain out of proportion and pain with passive stretch are early findings; pulselessness is a late/ominous sign - Pressure measurement: absolute >30 mmHg or delta pressure (diastolic BP - compartment pressure) <30 mmHg indicates fasciotomy - Tibial fractures are the most common cause; delay in treatment leads to Volkmann-type contracture and rhabdomyolysis --- ## Case 3: Medial Meniscus Tear ### Clinical Image ![Meniscus Anatomy](case_03_image.jpg) *Source: [Wikimedia Commons - Meniscus](https://commons.wikimedia.org/wiki/File:Knee_meniscus.png) - CC BY-SA 4.0* ### Case Presentation A 45-year-old recreational tennis player presents with 6 weeks of right knee pain and intermittent mechanical symptoms. He recalls a twisting injury to his knee while playing tennis when he pivoted on a planted foot. He has had persistent medial-sided knee pain, worse with squatting and going up and down stairs. He reports episodes where his knee "catches" and occasionally "locks" in a flexed position, requiring him to wiggle the knee to unlock it. Physical examination reveals mild joint effusion. There is tenderness along the medial joint line. McMurray test is positive - rotating the tibia externally while extending the knee from a flexed position produces a painful click at the medial joint line. Thessaly test at 20 degrees of knee flexion reproduces medial pain. There is no ligamentous instability. MRI demonstrates a complex tear of the posterior horn of the medial meniscus extending to the inferior articular surface. Given his age, mechanical symptoms, and failure of conservative management, he undergoes arthroscopic partial meniscectomy with debridement of the unstable fragment. ### Key Learning Points - The menisci are C-shaped fibrocartilage structures that deepen the tibial plateau and improve load distribution - The medial meniscus is more commonly injured (less mobile, attached to MCL and capsule) - Meniscal tears often occur with rotational force applied to a flexed, weight-bearing knee - Mechanical symptoms (catching, locking) suggest a displaced fragment; locking in flexion is classic for bucket-handle tear - McMurray test: external rotation + extension tests medial meniscus; internal rotation tests lateral meniscus