Decreases in muscular strength, endurance, and angular velocity have previously been demonstrated in the elderly. Osteoarthritis (OA), especially of the knee, may cause further reductions in these parameters and lead to functional limitations. This study measured the effects of a quantitative progressive exercise muscle rehabilitation program (QPE) that was added to a physical therapy (PT) program. Forty subjects (20 men and 20 women) with OA of the knees were randomly selected from a group of volunteers (N = 437) for the 3-month program. Measurements of strength, endurance, angular velocity, and the Jette Functional Status Index were determined before and after 1, 2, and 3 months of the program. The QPE program was composed of isometric, isotonic, isotonic with resistance, endurance, and speed contractions prescribed in a progressive sequence. Muscle strength (14% and 29%) and endurance (38% and 43%) increased significantly (p < 0.05, ANOVA for repeated measures) for both the quadriceps and hamstrings, respectively, after rehabilitation. There were marked decreases in walking time and the difficulty and pain experienced during functional activities.