Department of Family Medicine (Dr. Siebert) and Department of Orthopedics & Sports Medicine (Dr. Kweon), University of Washington, Seattle siebert@uw.edu
The authors reported no potential conflict of interest relevant to this article.
These fractures occur as a direct blow to the front of the knee, such as falling forward onto a hard surface, or indirectly due to a sudden extreme eccentric contraction of the quadriceps muscle. Nondisplaced fractures with an intact knee extension mechanism, which is examined via a supine straight-leg raise or seated knee extension, are managed with weight-bearing as tolerated in strict immobilization in full extension for 4 to 6 weeks, with active range-of-motion and isometric quadriceps exercises beginning in 1 to 2 weeks. Serial x-rays also are obtained to ensure fracture displacement does not occur during the rehabilitation process.9
High-quality evidence guiding follow-up care and comparing outcomes of surgical and nonsurgical management of patella fractures is lacking, and studies comparing different surgical techniques are of lower methodological quality.10 Nevertheless, displaced or comminuted patellar fractures are referred urgently to orthopedic surgical care for fixation, as are those with concurrent loose bodies, chondral surface injuries or articular step-off, or osteochondral fractures.9 Inability to perform a straight-leg raise (ie, clinical loss of the knee extension mechanism) suggests a fracture under tension that likely also requires surgical fixation for successful recovery. Neurovascular injuries are unlikely in most patellar fractures but would require emergent surgical consultation.9
Ligamentous injury
Tibiofemoral joint laxity occurs as a result of ligamentous injury, with or without tibial plateau fracture. The anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL) comprise the 4 main ligaments of the knee. The ACL resists anterior tibial translation and rotational forces, while the PCL resists posterior tibial translation. The MCL and LCL resist valgus and varus stress, respectively.
Ligament injuries are classified as Grades 1 to 311:
Grade 1 sprains. The ligament is stretched, but there is no macroscopic tearing; joint stability is maintained.
Grade 2 sprains. There are partial macroscopic ligament tears. There is joint laxity due to the partial loss of the ligament’s structural integrity.
Grade 3 sprains. The ligament is fully avulsed or ruptured with resultant gross joint instability.
Vascular injury can lead to irreversible tissue damage and even limb loss if not promptly identified.
The decision to pursue surgical repair of a knee sprain depends heavily on the likelihood of keeping or regaining and maintaining functional joint stability during the injury recovery and postinjury time periods. Injuries that do not result in joint instability or injuries with a high likelihood of returning to a stable state with conservative measures often do not require surgical intervention.
