200 Section - Cramping, Atrophy, and a Baker’s Cyst: A Case Report on ALS Misattributed to a Musculoskeletal Pathology

Tuesday, May 19, 2026

6:00 PM - 7:30 PM PT

Presenting Author/Autor expositor(s)

AJ

Ashley Joss, n/a

Medical Student
PNWU-COM
Spokane, Washington, United States
DK

David Kim, MA

Medical Student
Pacific Northwest University of Health Sciences
Seattle, Washington, United States

Co-Author/Coautor(s)

JL

John F. Long, D.O., DO

Physician
Spokane Spine Center
Spokane, Washington, United States

Case Diagnosis: Amyotrophic Lateral Sclerosis (ALS)

Case Description: 62-year-old female patient with a medical history of transient ischemic attack (TIA), chronic obesity, and right knee derangement presented with posteromedial right knee pain, initially attributed to a Baker’s cyst. She reported an inability to dorsiflex or extend her right foot but denied lumbar radicular symptoms. The physical exam was significant for tongue fasciculations and atrophy, as well as right distal lower extremity muscle atrophy, weakness, and frequent cramping. Although the patient reported a prior history of stroke, there was no evidence of prior stroke on imaging or with clinical correlation.

Discussions:

This unique case of ALS emphasizes the importance of electrodiagnostic studies (EDX), including EMG and NCS, in differentiating ALS from peripheral neuropathies or benign musculoskeletal conditions, such as Baker’s cysts. EMG and NCS are crucial in confirming widespread lower motor neuron involvement consistent with ALS. These tools are especially helpful when differentiating ALS from other conditions that have overlapping presentations, such as stroke, cervical myelopathy, radiculopathy, or inclusion body myositis. The disadvantages of EMG and NCS are operator dependence, patient tolerance and compliance, concomitant diseases, and loss of nerve conduction with aging. However, despite some limitations, EMG and NCS ultimately help facilitate appropriate and timely referral to appropriate rehabilitation services.

Conclusions:

This case illustrates how neuromuscular disease can be masked by a localized musculoskeletal complaint, delaying accurate diagnosis. Although this patient displayed classic ALS symptoms with distal weakness, atrophy, and fasciculations her presentation was initially attributed to a Baker’s cyst. This underscores the importance of EDX especially when considering clinically misleading presentations as in this case study. This case reflects the profound psychosocial impact of an ALS diagnosis. Therefore, future research could focus on identifying red flags in patient presentations and examining systemic, socioeconomic, and emotional barriers that lead to diagnostic delays or follow-up gaps.