Article

 

  Too often, sports medicine clients are progressed through their rehabilitation programs based on a panacea of intuition and the bandwagon philosophy of “we have always done it this way.”  These beliefs are not individualized to appropriately meet the needs of the patient nor do they utilize scientific evidence from the literature.  This type of practice needs to cease to exist in the area of sports physical therapy if our profession is to be deemed worthy of the autonomy and respect it deserves.  Rather than rely on intuition to determine rehabilitation progression, experienced clinicians recognize the importance of a systematic evidence-based process.  This decision process is also based on subjective, objective, functional and “best” practice guidelines from the current literature.  Serial testing and retesting is at the core of this type of approach and it is utilized to answer the question of when the patient’s rehabilitation may be progressed.  The remainder of this article will describe in detail a functional testing algorithm (FTA) for rehabilitation and return to sport following anterior cruciate ligament reconstruction (Figure 1).  However, this type of evidence-based algorithm approach may be applied in the rehabilitation of all sports/orthopaedic musculoskeletal conditions.  In these cases the specific criteria and testing instrumentation may be different than those that are described in this article, however, the concepts of subjective questioning, objective serial testing, and functional assessment will remain the same.

 

A review of the literature from the 1970s and 1980s reveals that at that time the anterior cruciate ligament (ACL) was the most frequently injured ligament of the knee ^1-3  One would hope that in the last 20 – 25 years we would have seen a decrease in these type of debilitating sports injuries.  However, with the enactment of Title IX and the explosion of popularity sports participation among the young adolescent, the exact opposite has been true.  It has been documented that female athletes have a four to sevenfold increased risk of anterior cruciate ligament (ACL) injury compared with their male counterparts playing at similar levels in the same sports.^4-9  Given these findings, rehabilitation of both male and female athletes following anterior cruciate reconstruction is a common occurrence in outpatient physical therapy clinics.  The functional limitation and disabilities associated with ACL insufficiency are well documented in the literature^10-17 and include deficits in the skills of balance, proprioception, running, twisting, cutting, jumping or landing.^{14, 18}  Many athletes undergo surgically reconstruction with their primary goal being the full return of all functional activities needed for their respective sports.  Therefore, the full return to sport becomes a primary long term rehabilitation goal of each physical therapy session.  To accomplish this goal succinctly and safely, the rehabilitation professional needs to be able to answer the questions of how and when they may advance the therapeutic exercises and modalities associated with ACL rehabilitation.

 

One way to systematically and objectively return an athlete to full sporting activities is through the use of a functional testing algorithm.  In using a functional testing algorithm (FTA) the clinician is able to evaluate both quantitatively and qualitatively the athletes activity progression safely.  The term FTA was originally described by Davies and Zillmer¹⁹ to describe a way in which the clinician can initially retain clinical control of testing and slowly decrease this control as the patient progresses to higher levels of testing.  For example, early in the FTA, a KT-1000 knee arthrometers (MEDmetric® Corp, San Diego, CA, www.medmetric.com) is used by the clinician to assess ligament stability.  With KT-1000 testing, the clinician has total control of the environment, the knee range of motion and the amount of force placed on the reconstructed knee.  As the patient progresses through the FTA, clinical control is lost as the testing procedures become more challenging and complex.  The patient continues through the FTA and is only allowed progression to the next level of testing if they pass the preceding test.  In this way the FTA does not allow the patient to be placed at risk with further testing.  Serial testing and retesting in this manner also allows the clinician to determine what functional limitations are present during that particular phase of the rehabilitation process.  Testing results provide the clinician with specific guidelines that may be used to determine what exercises and skills the patient should perform in order to be successful with subsequent testing and retesting.

 

Although we use a similar testing protocol as described by Davies¹⁹, we have altered his original program based on the equipment and testing equipment that is available in our individual clinics.  Furthermore, clinicians without access to the isokinetic testing equipment described later will have to substitute this form of strength testing with alternative equipment such as a Smith Squat rack and a knee extension machine.  Modifications to avoid stressing the ACL tissue graft and ensure patient safety will have to be designed into the testing protocols.  Careful communication with the treating orthopaedic surgeon is paramount in these cases.  Regardless of what instrumentation a clinician decides to use, it is critical to recognize whether the testing protocol is reliable and valid.  Furthermore, whatever methods of balance or strength testing one decides to use, the concepts of serial testing and logical progression originally described by Davies^{19, 20} remain unchanged.

 

 

 

The initial phases of the FTA begin with the examination and evaluation of several basic measurements including subjective questionnaires, visual analog pain scales, range of motion goniometric measurements and kinesthetic and proprioceptive tests.  The use of scoring systems in which the patient rates knee function are an excellent tool to track an athlete’s confidence in his or her progress and self awareness.  Tools such as the Cincinnati and Lysholm scoring systems have been shown to be reliable and valid.²¹  Visual analog pain scales are also an easy method to assess subjective criteria in an objective manner.  Recently, Crossley et al. has shown that visual analog pain scales are a reliable method to monitor outcomes in individuals with patellofemoral pain.²²  In the FTA, a visual analog pain scale greater than 2 or 3 out of 10 needs to be investigated.  Weekly girth or anthropometric measurements should be included in documenting a patient’s progress following ACL reconstruction.  Girth measurements are taken at 15 cm distal to the knee joint line, at the joint line, and at 10 cm and 20 cm proximal to the joint line to assess joint effusion and muscle atrophy following surgery.  Measurements are taken in centimeters and compared to the uninvolved lower extremity.  The reliability of these type of girth measurements following ACL surgery has been documented in the research literature.²³  Empirically, a patient’s exercise intensity and duration is not progressed if a difference of greater than 1 cm exists at the joint line.  It is important to note that a difference of a cm is relatively common during the early stages of rehabilitation however, a difference of 1 cm at 6-12 weeks following the reconstruction procedure in a knee that demonstrated equal measurements during the previous PT visit is an example that the patient did not tolerate the rehabilitation program at their last visit or may be evidence that they are irritating the knee outside of physical therapy.  Finally, range of motion measurements may be taken with a standard goniometer and should be within 10 percent of the uninvolved knee prior to beginning any other testing.  In summary, basic measurements should be recorded on a weekly basis at minimum.  Changes in pain, joint line anthropometrics and range of motion provided subjective and objective data the clinician can use to determine if the patient is ready to progress to the next phase of rehabilitation.

 

 

KT-1000 Knee Arthrometer Testing

 

Following basic measurement testing, a KT-1000 knee arthrometer is used to manually assess the laxity associated with the reconstructed anterior cruciate ligament graft tissue.  The KT-1000 is an instrument that measures either anterior or posterior tibial translation.  This difference in translation is measured by the arthrometer monitoring the translation of motion in millimeters between two sensor pads, one in contact with the patella and another in contact with the tibial tubercle (Figure 1).^{10, 24-27}  Anterior translation measurements are only valid if the posterior cruciate ligament is intact or posterior cruciate laxity has been measured with the arthrometer prior to ACL testing.  The knee is placed in 30 degrees of flexion and the arthrometer is aligned and secured to the patient’s tibia.  Anterior tibial translation is then recorded under the following five loads / conditions: anterior translation forces of 15 lb, 20 lb, and 30 lb, a manual maximum force and an “active quadriceps” measurement taken with the patient performing a short-arc knee extension.  According to the research by Daniels et al., a right to left difference of less than 3 mm is desirable and classified as normal physiological laxity.  A right to left difference on any test of 3 mm or more is classified as pathologic.^{10, 25, 26}

 

 

 

If ligament integrity is determined to be acceptable, we then test kinesthesia and proprioception.  Balance has been described as the body’s coordinated neuromuscular response to maintain equilibrium.²⁸  If computerized instrumentation such as the Balance System (Biodex Medical Systems, Shirley, NY) is available it should be utilized.  However, as mentioned previously often this type of testing equipment is unavailable in the small private practice or hospital outpatient setting.  Therefore, alternative tests and less expensive equipment are substituted.  The one legged stance or “stork” test²⁹ is probably one of the oldest known methods to evaluate balance that is described in the rehabilitation literature.  However, this test is usually not a sensitive test in the young athletic population.  Most athletes can stand unilaterally on their involved lower extremity without difficulty within two to three weeks post operatively.  In addition, the stork test can only be used to evaluate static balance.  For this reason we use a dynamic balance test known as the Lower Extremity Functional Reach Test (LEFRT).^30-32  In this test the participant uses a single-leg stance position to reach with the contralateral leg as far as possible in multiple directions (Figure 2A and 2B).  The distance from the toes of the stance foot to the toes of the reaching foot is recorded.  The participant is asked to reach in a controlled manner.  Loss of balance, touching completely down with the reaching foot or touching with either upper extremity is not allowed.  The distance reached with the uninvolved extremity is compared to that of the uninvolved extremity.  Research has shown that the test / retest reliability of the LEFRT is quite high.^{30, 32}  In order to advance to the next stage of testing in the FTA the goal of a balance deficit of less than 10% to the uninvolved lower extremity must be met.  If the patient is unable to meet this criteria then activities incorporating the balance test itself or balance tasks are integrated into the rehabilitation plan.

 

 

 

Once the patient has successfully met the specific criteria or normative data of the basic tests of the FTA then it is time to assess muscular strength and power.  It should be recognized that these strength and power tests are only carried out when the following two criteria have been met.  First, sufficient bone and soft tissue healing time must have occurred.  This time period will be dependent on many variables such as graft choice, surgical method, age of the patient, additional injuries, etc.  Second, with all testing methods and equipment a gradient warm-up or submaximal test should be provided.  If pain or apprehension is present during this warm-up or submaximal testing period, then testing is discontinued. 

 

In the FTA following ACL reconstruction, closed kinetic chain testing precedes open kinetic chain strength testing.  Like the original FTA first described by Davies¹⁹, isokinetic testing over a velocity spectrum is utilized.  Results are interpreted based on normalized peak torque to body weight data, comparison to the uninvolved extremity, unilateral agonist/antagonist peak torque ratios, and normative data from the literature.²⁰  The Lido Linea (Loredan Biomedical, West Sacramento, CA) is the preferred closed kinetic chain (CKC) isokinetic device to determine strength.  The Lido Linea is used in a semi recumbent position, which more accurately reflects the position of the body during functional activities.  A reciprocal stepping motion is also utilized, as it is thought that this better represents functional activities of walking or running.  Testing velocities are slow at 10-inches per second (25.4 cm), medium at 20-inches per second (50.8 cm) and fast at 30-inches per second (76.2 cm).  The reliability of the Lido Linea has been shown to be consistent with intraclass correlation coefficients of .85 to .94.³³  It is with CKC isokinetic testing that strength of the entire lower extremity is assessed.  Because CKC isokinetic testing involves contributions from the hip, knee, ankle, and foot, specific deficits of any single muscle group may go unnoticed if compensated for by other muscles in the lower extremity kinetic chain.³⁴  Empirically, we have found that deficits of as little as 5% on CKC testing may reveal 20-30% deficits in the isolated quadriceps and hamstring muscle groups.  Therefore following CKC isokinetic testing, an open kinetic chain (OKC) test is always performed to ensure that no weakness exists in the quadriceps or hamstring muscles. 

 

Like CKC testing, OKC testing is also performed throughout the velocity spectrum.  Speeds of 90, 180, and 300 degrees per second are commonly used.  To avoid undue stress to the surgical reconstruction during OKC testing, an extension range of motion stop is placed at 30 degrees of knee flexion.  Wilk and Andrews and others have previously demonstrated that with peak knee extension the tibia is translated anterior greatest between the ranges of 30 and 15 degrees of knee extension.^35-38 Tibial pad placement during isokinetic testing is also somewhat controversial.  We agree with others who use a proximal tibial pad placement at about mid tibia to decrease anterior shear forces produced by the quadriceps extensor mechanism.^{20, 39, 40}

 

 

 

 If strength has proven acceptable for the given time frame, the patient is progressed to actual functional jump and hop testing.  Up to this point the clinician has retained clinical control of his or her patient since they have determined range of motion limitations, forces through the reconstructed graft, and velocities of movement.  When jumping and hoping tests begin, a large portion of clinical control is lost.  Our functional testing begins with the two-legged jump test.  A jump test by definition uses a double-legged motion or pattern.¹⁹  Manske et al have shown that the jump test is extremely reliable, even following isokinetic testing.⁴¹  This is in agreement with other investigators who have found the two-legged jump test to be very reliable.^{42, 43}  Hands can be held behind the back¹⁹ or on the hips⁴¹ to prevent additional contributions from the head, trunk and arms(Figure 3).  Four gradient warm-ups (25%, 50%, 75%, and 100% effort) are used so that the patient can practice and fully understand the testing procedure.  Testing is discontinued if pain or obvious apprehension is apparent during the warm-up jumps.  Following the gradient warm-up, the patient is allowed three maximal volitional attempts.  Both the quality and quantity of the jump is evaluated.  Many times the patient is ready to perform the concentric portion of the jump, yet appear hesitant during the eccentric landing of the jump.  This can be seen as the patient favoring the injured extremity by landing more on the uninvolved leg.  This is an excellent example of how qualitative data as well as quantitative date may be gleaned from this type of functional test.  At present, no research is available describing jump performance following various knee injuries.  Therefore, we score the jumps normalized to the patient’s own height.  Men are expected to jump about 100% of their height, whereas women should jump 90% of their height.¹⁹  If the patient is able to jump the appropriate distance with two legs, the single-leg hop test can be performed.  Similar to the jumping protocol, four gradient warm-ups are given, followed by three maximal volitional hop attempts.  During the single-leg hop test the patient jumps off of the involved leg and lands on the involved leg.  This can be compared to the uninvolved leg.  As with the two-legged jump, the patient is asked to hold either his/her hands on hips or behind their back to minimize head and trunk movements (Figure 4).  Scores are compared bilaterally as well as normalized to the patient’s own height.  The patient’s psychological willingness to land on the single injured leg is tested when the patient is asked to land on the single post surgical extremity.  When performing the single-leg hop test, male patients should be able to hop 80-90% of their height, while female patients should be able to hop 70-80% of their height.  Additionally each should be able to hop within 10% of their uninjured extremity. 

 

The final test that we perform is the Lower Extremity Functional Test (LEFT).  This test was devised after attempting multiple tests to clinically assess multiple functional lower extremity movement patterns that may be assessable following surgery.  The LEFT test is unique in that it has many functional movement components in one single test (Video Clip).  Negrete and Brophy have proven that the LEFT is valid and correlates with other tests of physical performance.⁴⁴  Tabor et al have shown that the LEFT is has excellent reliability.⁴⁵

 

 

 

Logical and scientific progression of a rehabilitation patient following ACL reconstruction is possible utilizing a functional testing algorithm based approach.  Although further investigation needs to be performed to assess its ultimate success, the use of the FTA serves as a blueprint from which the sports medicine clinician may set goals, establish protocol guidelines, and safely determine timelines for return to sport.  Certain aspects of physical therapy will always remain an art based on the “hands-on” skills of the clinician, however, clinical reasoning and rehabilitation progression decisions must be based on a scientific foundation of evidence-based practice.  Utilization of an algorithm based functional testing approach as described above can make this a reality.

 

 

 

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Robert C. Manske, MPT, MEd, SCS, ATC, CSCS