Chronic anterior knee pain is a common complication following intramedullary nailing of a tibial shaft fracture. The source of pain is often not known nor is the reason for a simultaneous decrease in thigh muscle strength. Anterior knee pain has also been reported following an anterior cruciate ligament rupture. No previous investigation has assessed whether weakness of the thigh muscles is associated with anterior knee pain following intramedullary nailing of tibial shaft fractures.
University Hospital of Tampere, University of Tampere.
Fifty consecutive patients with a nailed tibial shaft fracture were initially included in the study. Ten patients did not have isokinetic strength testing for various reasons and were eliminated from the study.
Main Outcome Measurements
Isokinetic muscle strength measurements were done in 40 patients at an average 3.2 ± 0.4 (SD) years after nail insertion (1.7 ± 0.3 years after the nail extraction).
Twelve (30%) patients were painless and 28 (70%) patients had anterior knee pain at follow-up. With reference to the hamstrings muscles, the mean peak torque deficit of the injured limb (as compared with the uninjured limb) was 2 ± 11% in the painless group and 11 ± 17% in the pain group at a speed of 60°/s (P = 0.09, [95% CI for the group difference = −18% to 0%]). At a speed of 180°/s, the corresponding deficits were −3 ± 13% and 10 ± 21% (P = 0.03, [95% CI for the group difference = −4% to −2%]). With reference to the quadriceps muscles, the mean peak torque deficit of the injured limb was 14 ± 15% in the painless group and 15 ± 15% in the pain group at speed of 60°/s (P = 0.71, [95% CI for the group difference = −11% to 10%]). At a speed of 180°/s, the corresponding deficits were 9 ± 11% and 14 ± 17% (P = 0.46, [95% CI for the group difference = −14% to 5%]).
Based on this prospective study, we conclude that anterior knee pain after intramedullary nailing of a tibial shaft fracture, although of multifactorial origin, may be related to deficiency in the flexion strength of the thigh muscles.