History: A 25-year-old male sustained a left knee hyperextension injury while being tackled by a friend in his backyard. He had immediate pain, swelling, and was unable to ambulate. X-Rays in the ED demonstrated an avulsion fracture of unknown origin. Patient was placed in a knee immobilizer and advised to follow up with orthopedics. Three days later, he presented to clinic with pain, swelling, significant instability, numbness and coolness in left foot, and inability to dorsiflex his left ankle.
Physical Exam: Knee examination revealed significant ecchymosis of the posterior-lateral aspect of the knee and positive effusion. Coolness and decreased sensation to distal one third of left leg. He had a positive foot drop. Difficulty palpating dorsalis pedis pulse. Good capillary refill. Significant laxity to lateral collateral ligament in full extension (0 degrees). Positive Lachman’s as well as laxity with posterior drawer testing.
Differential Diagnosis:
1. Knee dislocation with peroneal neuropraxia and possible popliteal artery injury 2. Multi-ligament left knee injury with peroneal neuropraxia and possible popliteal artery injury
Tests and Results: CT angiogram- No arterial injury
MRI - Edema and nonorganized hematoma involving gastrocnemius, soleus, popliteus, and tibialis anterior. Detached medial and lateral patellar retinaculum, medial and lateral meniscus tears. Partial tear of PCL, MCL strain, ruptured ACL and LCL. Thin but intact peroneal nerve noted. Avulsion fracture of biceps femoris and tear of popliteus tendon. Medial femoral condyle osteochondral impaction fracture.
Final Working Diagnosis:
Multi-ligament left knee injury. Avulsion fracture of biceps femoris. Meniscal tears. Peroneal nerve injury without arterial injury.
Treatment and Outcomes:
1. Surgical repair 2 weeks after injury.
2. Extensive rehabilitation (0-6 weeks post-op: ROM exercises 0-90; 6-12 weeks post-op: strengthening exercises and advancing weight bearing 25% weekly).
3. Functional brace.
4. Continued monitoring for peroneal nerve improvement in motor and sensation.
4. Had discussion with patient regarding limited outcome and primary goal of function.
5. Unlikely to return to sport.