Effect of foot balance on the intra-articular pressure in the distal interphalangeal joint in vitro.

REASONS FOR PERFORMING STUDY Increased joint pressure has been implicated in the progression of osteoarthritis. HYPOTHESIS That intra-articular pressure in the distal interphalangeal joint (DIP) is significantly higher in legs loaded with heel up (HU), low heel (TU), lateral side up (LU) and medial side up (MU) imbalance compared to the balanced position. METHODS Twelve elbow down limbs were compressed in a hydraulic loading jig and DIP pressure measured. RESULTS Elevating the heels by 5 degrees significantly increased DIP pressure. After 5 ml of contrast was injected into the joint, heel elevation caused a greater increase in DIP pressure and heel lowering decreased DIP pressure. Silicone rubber castings were taken of 20 DIP whilst under load. The articular contact area was localised on the dorsal aspect in the HU position, palmar aspect in the TU position and towards the elevated side with lateromedial imbalance. CONCLUSIONS Altered foot orientation, which could result from trimming and shoeing, therefore influences intra-articular pressure in the DIP and the articular contact area. POTENTIAL CLINICAL RELEVANCE The results support the view that a balanced foot is the ideal and that the elevated heels may be detrimental to long term viability of the DIP joint.