Background/Purpose:   The elbow extension angle (ELB) is commonly given as 180o although most healthy females exhibit hyperextension(1).  The loss of hyperextension (LOH) in a female is the earliest sign of elbow arthritis(2) and can be regarded as evidence of organic disease.  Therefore, diseases commonly involving the elbow, such as rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE) might be associated with LOH whilst diseases such as osteoarthritis (OA), which does not alone affect the elbow, or fibromyalgia (FM), a non-organic disorder, would be expected to maintain normal ELB.  A trained clinician can estimate the ELB accurately(3).  One of us (Case) has been recording the ELB as neutral, hyperextended, or contracted in female patients at the time of 1st rheumatologic contact.  To test the hypothesis that ELB may be used as a diagnostic tool in early arthritis we reviewed the scanned electronic medical record at our institution for the period January 1, 2003 – December 31, 2007.

Methods:   All outpatient female patients were eligible.  The primary rheumatologic diagnosis at the time of last follow-up was used.  The ACR disease criteria available during the study period were observed.  All study patients with RA and SLE met criteria; FM patients were included if they exhibited diffuse pain with multiple diffuse tender points (not necessarily 11 of 18).  The Mann-Whitney U test was used to distinguish disease subgroups, and Spearman’s correlation to compare age and duration of disease with LOH.  Statistics were done with SPSS.                             

Results:    The charts from 717 patients were available.  Of these, 396 had the initial ELB recorded (55%).  (Most of the remainder had exclusively lower extremity-directed exams; data not shown.)  106 of these had disease onset of less than one year.  They had a mean age of 51.0 (SD 14.1) years and were followed for a mean of 2.1 (SD 3.0) years.   The final diagnoses were RA in 31 (29.2%), OA in 20 (18.9%), SLE in 7 (6.6%), FM in 14 (13.2%), other in 34 (32.1%).  FM could be distinguished from RA (p=0.005) and SLE (p=0.04) but not from OA (p=0.062).  RA could not be distinguished from SLE (p=0.874).  Only one in 14 FM patients evidenced LOH.  These findings are expressed in the Figure.  Among the 396 patients with disease of any duration, RA could be distinguished from OA (p<0.0001) and FM (p<0.0001); FM, however, could not be distinguished from SLE (p=0.316).  An observed LOH in FM was correlated with duration of disease (p<0.0001) but not with age (p=0.280).

Conclusion:   The hypothesis that early LOH was associated with RA and SLE but not with FM was confirmed.  Early FM rarely had LOH whereas RA and SLE commonly did.  Measurement of the ELB is potentially a new diagnostic sign in the rheumatologic exam.  References:

(1)    Amis et al, Clinics Rheum Dis (1982) 571-591

(2)    Lockie, Arthritis and Allied Conditions (1982) p. 22

(3)    Blonna et al, Knee Surg Sports Traumatol Arthrosc (2012) 20:1378-1285