Working Diagnosis:
Complete MPFL disruption, MCL tear, and avulsion fracture of the medial patella

Treatment:
The patient failed conservative management with functional rehabilitation and pain control. He was given a patellar stabilizing brace and referred to an orthopedic surgeon given his recurrent patellar instability.

Outcome:
He underwent a successful right knee arthroscopy with MPFL reconstruction using hamstring allograft and patella chondroplasty. He completed post-operative physical therapy.

Author's Comments:
The patient's recurrent instability likely predisposed him to an atraumatic MPFL tear. The natural tendency of the patella is to laterally dislocate, tearing the MPFL in the process. Acute patellar dislocation is easily observed on exam, but many patients self-reduce their injuries before presenting. MPFL tears can be diagnosed on ultrasound and MRI. In this case, the suspicion was high despite an unusual mechanism of injury. Non-operative management includes a patellar stabilizing brace, NSAIDs and icing to reduce pain and swelling, and rehabilitation of the surrounding structures to allow for tissue healing and optimizing mechanics to restore stability. Referral for surgery is indicated when non-operative treatments fail.

Editor's Comments:
Patellar instability is a common cause of acute and chronic knee pain. The diagnosis is made easily when the patient presents with the patella dislocated, but often it self-reduces. In these cases, care should be taken to distinguish patellar dislocation from other causes of instability such as ACL tear. Physical exam findings suggestive of patellar instability include effusion in the acute setting, tenderness over the MPFL, tenderness over the lateral femoral condyle and medial patellar facet due to bone contusions, and patellar apprehension. In patients with hypermobility contributing to patellar instability, the physican should asess for other joint hypermobility and consider connective tissue disorders.

References:
Krebs C, Tranovich M, Andrews K, Ebraheim N. The medial patellofemoral ligament: Review of the literature. J Orthop. 2018;15(2):596-599. Published 2018 May 7. doi:10.1016/j.jor.2018.05.004.
Rogers DL, Cosgarea AJ. Evaluating Patellofemoral Patients: Physical Examination, Radiographic Imaging, and Measurements. Clin Sports Med 41 (2022) 1-13.
Colombi M, Dordoni C, Chiarelli N, Ritelli M. Differential diagnosis and diagnostic flow chart of joint hypermobility syndrome/Ehlers-Danlos syndrome hypermobility type compared to other heritable connective tissue disorders. Am J Med Genet C Semin Med Genet. 2015 Mar;169C(1):6-22.

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