By participating in this study, it will not alter the standard of care provided during the course of the patient's rehabilitation in physical therapy. During the initial physical therapy evaluation, a member of the research team will determine if the patient would like to participate in the study and if they choose to do so they will then be consented. Based on the clinical presentation the standard evaluation will determine the primary limitations of the knee joint and surrounding soft tissue structures and outline the best course of manual physical therapy intervention deemed appropriate.
Should the patient choose to participate, they will then complete a pre-test maximal isometric contraction in the knee extension machine in the physical therapy clinic; this is an exercise device commonly used to strengthen the quadriceps muscles for patients with various types of lower extremity pathology. Patients will be monitored for any changes in pain during this screening pre-test in accordance with the Physical Therapy service standard operating procedures; those whom pain increases more than 3/10 points on the numeric pain rating scale from baseline will be excluded from this study and will be counted as screen failures; all others will be included in the study. The patient will then be provided an appointment slip to meet the research team at the Army-Baylor Center for Rehabilitation Research Biomechanics Lab at the Army Medical Department Center and School where all formal testing for this study will take place. All laboratory data will be collected for the bilateral lower extremities.
When the subject reports to the lab the following sequence will occur. They will be provided with an intake form to collect all baseline data, Western Ontario and McMaster Universities Osteoarthritis Index, and numeric pain rating score. Pain scores will be elicited throughout the testing procedures to ensure patient safety and comfort per the PT service pain assessment standard operating procedures. Pain pressure threshold will be obtained using a handheld algometer as an adjunct to the numeric pain rating scale to better quantify their pain levels. Pain pressure threshold measures will be collected bilaterally over the Tibialis Anterior muscle belly approximately 2.5cm lateral and 5cm inferior to the tibial tubercle. A Timed up and Go test will then be administered using an accelerometer worn by the patient around the waist and bilaterally on the dorsum of the foot to quantify the velocity in which they complete the test among the various phases (sit/stand, walking, turning). This will be followed by the first isometric testing session to determine the baseline voluntary quadriceps activation and rate of torque development.
Subjects will undergo assessment of neuromuscular function using a combination of voluntary and evoked contractions. All test procedures will be performed on the unaffected limb first, followed by the affected limb. Electrically-evoked contractile properties will be tested first, followed by volitional strength, voluntary activation, then rate of torque development.
Subjects will be seated on the chair for the HUMAC NORM testing and rehabilitation system with the hips and knees flexed to 85 degrees and 60 degrees, respectively. A shin attachment from the dynamometer will be secured around the subjects' lower leg so that the distal end of the pad is approximately 5 cm proximal to the distal end of the tibia anteriorly.
Two-inch by four-inch self-adhesive muscle stimulation electrodes will be applied over the muscle bellies of the distal vastus medialis and proximal vastus lateralis. Subjects will then undergo evoked twitch contractions starting at 50mA (400 V, 1000 µsec pulse width) using a constant current muscle and nerve stimulator (Digitimer Ltd., Model DS7R, Hertfordshire, England) while sitting at rest. This process will continue until the evoked torque reaches a plateau, at which point it will be terminated. The purpose of this testing is to determine the lowest intensity of current necessary to evoke maximal quadriceps torque for each subject. The amount of current necessary to achieve peak evoked twitch torque will be used for all future evoked contractions. After this, muscle speed properties will be assessed using 3 maximal twitches, followed by 3 maximal doublets at 100 Hz, all 10 seconds apart from each other. This will be done for a total of 6 evoked contractions. The purpose of this is to obtain information related to the peripheral speed properties of the muscle (e.g., rates of rise and relaxation for torque).
Maximum volitional isometric contraction testing will be assessed next. Strength testing will begin by having subjects perform 3 sub-maximal (50%, 75%, 90% maximum effort) isometric knee extension contractions to familiarize themselves. After familiarization, subjects will perform at least 2 maximal voluntary isometric contractions of the quadriceps muscles to determine the peak voluntary knee extensor force each subject can generate. For reliability, the researchers will require two contractions that produce similar values of torque (defined as no more than 5% difference between trials). After peak torque has been reliably identified, quadriceps activation will be tested with the interpolated doublet technique (IDT).\[30\] This test includes at least two five second maximal voluntary isometric contractions during which a doublet at the stimulus intensity determined in step one is introduced when the torque produced by the subject reaches a threshold determined during maximal voluntary isometric contraction testing. A second stimulus of equal intensity is delivered shortly after the subject returns to rest after each trial in order to assess the muscle in its potentiated state. Two minutes rest will be provided between each of the trials. To produce inter-trial reliability similar to strength testing, the researchers will require two contractions that produce similar values of voluntary activation (defined as no more than 5% difference in voluntary activation between trials).
Rate of torque development will be measured after completion of maximal voluntary isometric contraction trials. A total of five valid repetitions will be completed lasting approximately one second in duration for each contraction. In order to count as a valid trial, the magnitude of torque attained during these brief contractions must exceed 75% of maximal voluntary isometric contraction. A rest period of 30 seconds between contractions will be given in order to allow for adequate rest. An enthusiastic and loud verbal cue will be provided for each contraction. Instructions to "kick as fast and as hard as possible" will be utilized as verbal cues have been reported to impact the type of motion the patient conducts. Visual feedback and loud verbal encouragement will be used to elicit the greatest amount of muscle activation possible.
Treatment will be initiated within ten minutes of completing the first isometric trial within the Army-Baylor Center for Rehabilitation Research. The researchers will utilize a pragmatic manual physical therapy approach that is customized to each subject. This approach will use targeted manual therapy techniques for the knee joint and soft tissues with complimentary therapeutic exercises to augment the movement impairment identified. All treatment will be performed by a board-certified physical therapist with advanced manual physical therapy fellowship training. The treatment provided will be evidenced-based and is standard care for a manual physical therapy trained provider. The timing of the treatment session is congruent with what is commonly observed in a physical therapy clinic and will last approximately 30 minutes in duration.
The control group will receive the same amount of face-to-face time with a physical therapist. The intervention will include a 30-minute educational class on knee osteoarthritis which will cover various topics to include a brief description of the pathophysiology, diagnosis, prognosis, and different treatment options available in addition to rehabilitation. The researchers will provide handouts on general exercise and joint sparing activities and conclude the brief with a question and answer session.
For post-treatment data collection, each subject will undergo testing for maximal voluntary isometric contraction, voluntary activation, and rate of torque development in the same manner as described above. For voluntary activation testing, the same stimulus intensity determined during pre-treatment data collection will be used. In addition, subjects will not require post-treatment assessment of the contractile properties of their quadriceps muscle group. The reason for not repeating this assessment is because electrically-evoked contractile properties quantify only peripheral physiologic properties of muscle and this study's intent is to measure changes attributed to central drive (i.e. changes within the motor cortex and/or spinal cord).
Immediately following the 30-minute treatment session, subjects will repeat the timed up and go test and rate their pain via the numeric pain rating scale. Immediately following this, the subject will undergo maximal voluntary isometric contraction testing, voluntary activation, and rate of torque development testing in the same manner previously described. The same stimulator settings used during the pre-test will be used for the post-test. At the conclusion of data collection, the researchers will ensure the patient has a follow-up appointment scheduled at the Brooke Army Medical Center physical therapy clinic for the initiation of their formal rehabilitation, thus ensuring that all subjects receive the standard of care for their knee pain. As all data will be collected on a single day in one session no email or phone calls will be required at the completion of the lab testing.
