Background. The goal of our research was to evaluate changes in vertical floor reaction force (N) in lower limbs of patients between the 14th and 18th week of physiotherapy after selected operations to surgically repair articular cartilage in the knee. Material and methods. We examined 55 persons, 25 of whom were recovering from surgical repair of articular cartilage in the knee. The subjects, divided into 4 groups, were examined on MTD-Balance tensometric platforms while ascending and descending steps (19 cm per step). We examined the changes in the vertical floor reaction force (N) in the operated and healthy limbs. The results obtained between the 14th and 18th weeks of physiotherapy were compared to those of persons without damage to cartilage. Results and conclusions. While ascending stairs, the patients and healthy controls showed a 20-28% increase in floor reaction force in comparison to standing on one leg. While descending, both the patients and the healthy controls showed 80-90% increases. The results were roughly similar and no statistically significant differences were observed.