Eight metatarsophalangeal (fetlock) joints were studied in anaesthetized young ponies. Pressure measurements were made in the joint and at various sites in the marrow cavity of the third metatarsal bone with simultaneous measurement of systemic arterial and venous blood pressures. Fetlock joint flexion was always associated with a statistically significant initial decrease in intra‐articular pressure (p<0.05) followed by a marked increase in pressure (p<0.05). Subsequent extension was accompanied by a similar pressure pattern, although there appeared to be a hysteretic relationship. Fetlock joint distension induced by incremental injection of saline caused a stepwise increase in the intra‐articular pressure.