Introduction: After knee injury or surgery, there is usually a marked weakness and atrophy of knee extensor muscles, especially m. quadriceps femoris. Strength and endurance of m. quadriceps femoris are of vital importance for normal knee joint function. An important underlaying factor of long-term m. quadriceps femoris weakness after knee injury is arthrogenic muscle inhibition. Regardless of resistance training m.quadriceps femoris strength remains unchanged or is even reduced due to arthrogenic muscle inhibition. Purpose: The aim of this diploma work is to evaluate the effectiveness of physiotherapeutic procedures for strengthening and activation of muscles in a patient with chronic m. quadriceps femoris weakness because of postoperative knee joint impairment. Methods: In diploma work a 44 year old patient is described, which was included in the 16 exercise units. The patient was tested and measured twice, before and after the therapeutic program. Inspection, palpation and goniometric measurements of knee joint were performed as well as measurements of lower limb circumference, skin fold and body mass, Y-balance test, single-leg step down test and measurements of maximal volitional isometric contraction of extensors and flexors of both knee joints. Results: Most of the measured variables of the operated leg improved after the therapeutic program. Lean thigh circumference of the operated leg increased distally by 1,3 cm (3,9 %), and proximally by 2,3 cm (5,5 %), the body weight of the patient increased by 3,1 kg, in the performance of the Y-balance test with the operated leg reach increased in anterior direction by 10,5 cm, posterolateral by 29,0 cm and posteromedial by 32,5 cm. Maximal volitional isometric contraction of knee joint extensors of operated knee increased by 6 Nm (14 %). Discussion and conclusion: We managed to achieve most of our goals, which are increase muscular strength and endurance, stimulate hypertrophy and disinhibition of m. quadriceps femoris of the operated leg, improve function and reduce pain in the operated leg, eliminate fear during walking and loading, and achieve normal gait pattern. Based on the results we can conclude that the choice of the protocol of physiotherapy procedures was appropriate and effective.