Disclosures: Michael Boeving, MD: No financial relationships or conflicts of interest

Case Diagnosis: Femoral neuropathy following non-contact lateral patella dislocation

Case Description: Here we present a case of a 32-year-old male referred for electromyography (EMG)/nerve conduction study (NCS) due to quadriceps/iliopsoas weakness. Patient was playing soccer 2 months prior and twisted his left knee while attempting a high kick resulting in a left lateral patellar dislocation. Relocation of the patella required several attempts and conscious sedation. On 2-week follow-up, the patient was found to have deep vein thrombosis requiring anticoagulation. He was then managed with bracing and physical therapy but by 6 weeks had significant refractory weakness prompting the referral.

Setting: OutpatientAssessment/

Results: Initial EMG/NCS, 2-months post injury, demonstrated a left femoral compound motor action potential (CMAP) 25% of the right femoral CMAP and acute denervation with significantly reduced recruitment isolated to the left vastus lateralis consistent with 3-/5 strength in iliopsoas and quadriceps strength testing. Patient reported improvement in the subsequent 3-6 months but had residual weakness and atrophy. At 12 months, repeat EMG demonstrated left femoral CMAP had improved to 75% of the right and EMG demonstrated no acute denervation with increased amplitude motor unit potentials with reduced recruitment.

Discussion: Femoral neuropathy has rarely been associated with patellar dislocation most notably in ballet dancers as well as at least one soccer player. In nontraumatic cases, the neuropathy is attributed to femoral nerve traction injury. More commonly, femoral neuropathies in sports are the result of traumatic iliopsoas hematoma compressing the femoral nerve. This case is an unusual presentation which was suspected due to femoral nerve traction but could also be due to nontraumatic iliopsoas hematoma resulting from therapeutic anticoagulant which is also rare. Regardless of the underlying cause, the patient demonstrated favorable, but incomplete, functional and electrodiagnostic recovery.

Conclusion: Femoral neuropathy is a rare potential complication of patellar dislocation that practitioners should be aware to direct appropriate workup and rehabilitation efforts.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/lateral-patella-dislocation-associated-femoral-neuropathy-a-case-report/