The first recommendation is to address any flexibility impairments once the individual has been cleared for exercise by the physician. This will probably have been assessed and worked on during rehabilitation therapy, but there will likely still be some lingering mobility issues, as people with knee replacements often experience post-operative muscle tightness. Stretching the muscles around the knee will be important to restore adequate flexibility. In particular,
the quadriceps group can become tight at the incision site and throughout the muscle. Specific stretching and myofascial release with a foam roller has shown to be beneficial for restoring flexibility. General stretching and myofascial release of the hip muscles, hamstrings, and calves will also help to maintain flexibility throughout the kinetic chain. Flexibility exercises should be done at a level that does not elicit pain and is within a comfortable ROM.
For strengthening the knee, most exercises are safe, if they are gradually progressed. Particular attention should be placed on the quadriceps and hamstrings to regain knee stability. Open-chain exercises with the knee straight or from 90 to 60 degrees will prevent excessive loading of the patella. Closed-chain exercises can be progressed appropriately within the acceptable range of 0 to 45 degrees with a progression to 90 degrees. General conditioning of the hip and ankle muscles should be included to address any deficits.
The client should have adequate strength, range of motion, and basic proprioception before progressing to more functional activities. Functional activity should progress what has been done in rehabilitation and must follow any precautions. The client should master basic functional skills before progressing to higher-level activity. For these clients, aquatic exercise is a great way to progress functional activity while de-weighting the joint. Aquatic exercise often is used to transition clients to higher-intensity land-based activity. The buoyancy of the water unloads the joint, allowing for more activity with lower amounts of pain.
Deficits in general balance may be evident due to disuse of the kinetic chain. Basic progression of balance activities would be appropriate if no pain is elicited. Low-level cardiovascular activity is indicated for these clients. Exercising on a bike or elliptical trainer is preferred over jogging or walking long distances.
Begin with isometric exercises or light resistance (ankle weights) to strengthen the quadriceps, hamstrings, and gluteals without putting undue pressure on the joint. These exercises can be performed in a pool to further reduce joint pressures. Move to body weight bilateral exercises (e.g., squats) to develop overall muscular and joint control while encouraging full ROM. Add external resistance to increase muscular strength and endurance if no pain is experienced. Progress to unilateral exercises (e.g., lunges and step-ups) to develop muscular control of the joint complex.
Focus on proper control and technique to make sure the patella and femur track correctly.
The following exercises are good options to use initially as the client is getting back into a more rigorous routine for strengthening the lower extremity:
• Standing terminal knee extensions: The client starts by standing on one leg with the non-supporting leg resting toes-down for support and the hands holding onto a chair, counter, or wall for support. The client then moves the support leg into 30 degrees of flexion, keeping the shoulders and hips over the heel, and then presses the knee of the supporting leg backward, actively contracting the quadriceps to move into full extension. Resistance bands can be added to increase difficulty.
• Wall slide/squat: The client begins with the feet comfortably under the hips and the back flat against the wall and slides down the wall until the knees are flexed (staying above 90 degrees or to tolerance)
and holds for 2 to 30 seconds. The client presses through the heels and returns to the starting position.
• Bodyweight squat: The client starts with the feet under the hips and the arms out for balance. The client begins the movement by contracting the glutes and hamstrings to pull the hips backward. Remind the client to flex naturally at the hips and allow the knees to flex until comfortable. The client must keep the knees in line with the hips and ankles.
• Single-leg squat: The client begins by balancing on one foot with the other leg flexed behind for counterbalance. The client initiates the movement by pulling the hips back, and then sinks the weight downward over the support-leg heel.