Working Diagnosis:
Femoral mononeuropathy after patellar dislocation

Treatment:
Patient was started on aggressive physical therapy, with a focus on strengthening of his right vastus medialis, hip abductors, core, balance, proprioception, and gait.

Outcome:
Patient continued therapy with partial improvement of his gait, but did not return to sport and was eventually lost to follow up.

Author's Comments:
Femoral neuropathy has rarely been described following patellar dislocations. Current literature reports only a handful of cases
(1). It is likely underestimated because most cases are self-limiting, with recovery occurring over days to months.

Editor's Comments:
This is an unusual case since this involves a distal traumatic injury causing proximal upstream musculature abnormalities. Typically, we see isolated femoral neuropathies in trauma, pregnancy, thigh hyperextension, tumor, abscess and renal transplant surgeries; all etiologies that directly impact the proximal femoral nerve. In the few cases patellar dislocation and concomitant femoral neuropathy the proposed mechanism of injury is extreme stretch at the inguinal ligament due to transmitted forces from the quadriceps (1). Though, there is no exact consensus at this time.
With this presentation it is always important to consider disuse atrophy, plexopathy, amyotrophy, peripheral neuropathy or radiculopathy (2). Should rehab, or presentation appear atypical, e.g. greater than the normal disuse seen in typical patellar dislocations, EMG should be an early next step. At this time physical therapy with the potential for surgical repair of patellar femoral ligament (to reduce quad traction) appear to be the treatment of choice

References:
1 Shin CS, Davis BA. Femoral neuropathy due to patellar dislocation in a theatrical and jazz dancer: a case report. Arch Phys Med Rehabil 2005;86:1258–60
2 J. Feinberg, S. Nadler, L. Krivickas Peripheral nerve injuries in the athlete. Sports Med. 1997 Dec;24(6):385-408.

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