Years spent cracking knuckles doesn’t predict OA
A case control study found no correlation between OA in the hands and habitual knuckle popping.3 Investigators recruited 215 patients 50 to 89 years old who had received a radiograph of their right hand during the previous 5 years and divided them into cases with OA (135 patients), and controls without OA (80 patients). Patients completed questionnaires assessing the prevalence (20%), frequency (1 to 20 times per day), and duration (26 to 36 years) of knuckle popping.
Patients most commonly popped proximal interphalangeal joints (15.9%) followed by metacarpal phalangeal joints (13.5%), distal interphalangeal joints (6.1%), and first carpal metacarpal joints (2.3%). OA most often affected the distal interphalangeal joint (68.4%), followed by the first carpal metacarpal (57.1%), proximal interphalangeal (54.1%), and metacarpal phalangeal joints (28.6%). Investigators found no difference in the prevalence of knuckle popping between cases and controls (18% in cases vs 23.2% in controls; P=.361).
When investigators evaluated total knuckle popping exposure in “crack years” (number of times per day multiplied by years) in the distal interphalangeal or metacarpal phalangeal joints, they found no significant association between crack years and OA (distal interphalangeal joint, mean 108 crack years; metacarpal phalangeal joint, mean 75 crack years).
50 years of knuckle popping without ill effects
An n-of-1 case control study found similar results.4 The researcher, a physician, popped only the knuckles of his left hand, twice a day, for 50 years. He compared his hands at the end of the trial and found no arthritis in either hand and no visible differences.
But knuckle popping does have a downside
A paper described 2 case reports of acute injuries sustained during attempted knuckle popping—a partial tear of the ulnar collateral ligament of the thumb and subluxation of the extensor tendon of the fifth digit.5 Both injuries were associated with forceful manipulation of the digits, and both resolved with conservative management within 4 weeks.