BIOMECHANICS OF PATELLA FUNCTION. PETER G. KRAMER, EdD, PT*

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1 l/86/ $02.00/0 THE JOURNAL OF ORTHOPAED~C AND SPORTS PHYSICAL THERAPY Copyright by The Orthopaedic and Sports Physical Therapy Sections of the American Physical Therapy Association Patella Malalignment Syndrome: Rationale to Reduce Excessive Lateral Pressure PETER G. KRAMER, EdD, PT* Patella malalignment syndrome is characterized by pain in the anterior portion of the knee. There can be numerous causes; however, the end result appears to be excessive lateral pressure on the patellofemoral articulation. This problem commonly affects athletes as an overuse injury. Standard conservative treatment attempts to decrease inflammation and increase strength whereas surgical techniques seek to correct the actual cause of the malalignment. The biomechanical approach advocated in this article employs the standard conservative treatments in addition to a passive forced technique designed to reduce lateral pressure by stretching the lateral retinaculum and patella compression to facilitate cartilage metabolism. The approach has proven effective in reducing symtoms and allowing early return to activity. Patella malalignment syndrome is a long recognized syndrome of pain in the anterior portion of the knee, ofteh associated with vigorous activity. This pain can be acute and severe, forcing the individual to walk with the knee held in full extension or it can be mild, intermittent, and chronic, causing the individual only minimal discomfort. Although pain is the chief symptom, patella malalignment syndrome can be associated with patella dislocation or repeated subluxation, knee effusion, locking, grating, or ~eakness.~.~ Patella malalignment problems are derived from congenital or acquired abnormalities which, according to Larson,' manifest themselves in three areas: 1) abnormal patellofemoral articulation, 2) deficiencies in the surrounding supporting soft tissues, 3) malalignment of the lower extremity. It is not uncommon to have a combination of these problems associated with this syndrome. It is the purpose of this article to describe the standard conservative and surgical approaches commonly used to relieve the symptoms of patella malalignment syndrome and to present additional conservative treatment protocol which can be beneficial in treating the symptoms and preventing surgery. 'Director of Physical Therapy, Copley Hospital, Washington Highway, Morrisville, VT ; and Associate Professor, Athletic Trainer, Johnson State College. Johnson. VT BIOMECHANICS OF PATELLA FUNCTION Before examining the problems caused by malalignment of the patella, it is important to understand normal patellar function. The patella is located anterior to the knee joint. It is a sesamoid bone partially encased in the common tendon of the quadriceps muscle group, slightly superior to its insertion on the tibia1 tuberosity. The undersurface of the patella and the patello-femoral articular surface d the femur are covered with hyaline cartilage and lubricated with synovial fluid. The quadriceps are responsible for extending the knee, often against an extremely large weightbearing load. The patella functions as a fixed single axis pulley deflecting the quadriceps tendon, increasing its angle of pull on the tibia, and giving a mechanical advantage to the quadriceps muscle group.'.9 In the extended position, the patella is located above the patellofemoral articular surface. As the individual goes to full flexion, the femur rotates posteriorly on the tibia, causing the patella to slide below the articular groove on the femur, covering and protecting the anterior portion of the knee joint. As the individual returns to a standing position, the quadriceps contract and the patella once again is pulled over the articular surface of the femur as it rotates anteriorly on the tibia. In the range between 20 and

2 302 KRAMER JOSPT Vol. 8, No. 6 Fig. 1. A, With the knee in extended position, the patella is located above the patellofemoral groove; B, in slight knee flexion, the patella is in the articular groove; C, during moderate knee flexion with the patella below the articular surface.

3 JOSPT December 1986 PATELLA MALALIGNMENT SYNDROME Fig. 2. Irregular patellofemoral articular surface. 30' of knee flexion, the patella is pulled most medial facets of the patellofemoral surface of the tightly against the ffmoral surface, causing the femur. Under normal conditions, this angle is apdeflection of the quadriceps tendon and providing proximately if the angle increases, the the mechanical advantage for kneeextension (Fig. groove is flattened, increasing the potential for 1). subluxation or abnormal tracking of the patella PATHOMECHANICS OF PATELLA FUNCTION through this groove (Fig- *). b) Patellar tilt. If the line extended from the Under circumstances9 knee extension is lateral articular facet of the patella is parallel or a and painless event. There are, however, converges with the line from the lateral condyle numerous conditions that can alter the normal patella, causing pain for the individual. of the patello-femoral groove, it is an abnormal Kettlekamp7 reviews some of the common causes condition and indicates increased lateral pressure of patella malfunction: with knee extension (Fig. 3). c) Patella alta. A high riding patella exists when Abnormalities in the Patellofemoral the infrapatella tendon is longer than the greatest Articulations diagonal length of the patella. Under normal cira) Increased sulcus angle. The sulcus angle is cumstances, the ratio between the two approxicreated by the lines drawn from the lateral and mates one (Fig. 4).

4 304 KRAMER JOSPT Vol. 8, No. 6 Fig. 3. Patellar tilt causing an increase in the pressure on the lateral portion of the patellofemoral surface. d) Chondromalacia patella. This is the actual erosion of the articular cartilage of the patella. Surrounding Soft Tissue Abnormalities a) Vastus medialis. This muscle attaches to the superior medial aspect of the patella. Under normal conditions, it exerts a medial force on the patella during knee extension. Atrophy of this muscle or an abnormally high insertion on the patella can reduce its mechanical efficiency in producing medial tension. As a result, the patella will have a tendency to drift laterally during - knee extension (Fig. 5). b) Vastus lateralis. This quadricep muscle attaches to the superior lateral surface of the patella. If this muscle is hypertrophied, has developed a contracture, or is not correctly neutralized by the pull of the vastus medialis, it will cause a lateral drift of the patella during knee extension (Fig. 5). c) Abnormalities in the patella retinaculum. The patella retinaculum is fascia which attaches to the medial and lateral surfaces of the patella and assists in its proper tracking. Medial laxity or lateral tightness will cause an abnormal shift of the patella against the lateral femoral condyles during knee extension. d) Generalized joint laxity can also be a causative factor in the patella malalignment syndrome. This may allow the patella to move abnormally during knee extension. Lower Extremity Malalignment which the 66Q,, Angle a) An increased breadth of the hips in relationship to femoral length. b) Genu recurvatum.

5 JOSPT December 1986 PATELLA MALALIGNMENT SYNDROME 305 c) Pes planus. d) Foot pronation. Regardless of the specific cause or causes of abnormal patellar function, the end result, according to Ficat and Hungerford2 appears to be excessive lateral pressure on the patellofemoral articulation. The actual cause of pain in the patella malalignment syndrome is still a matter of debate. Hyaline cartilage is the tissue receiving the greatest abuse in this syndrome, but it is devoid of sensory nerve fibers. It is theorized that the pain comes from subchondral bone or from the surrounding synovial tissue as the result of a general inflammatory reaction.=16 CLINICAL PRESENTATION OF PATIENTS It has been my experience over the past 10 years that the patients suffering from patella malalignment syndrome fall into one of three general categories: 1) Young people (early teens) often just beginning athletic careers. In this group, girls will normally outnumber the boys:they will complain of pain associated with activity, usually localized on the superior and possibly medial aspect of the patella. Initially, pain will be noticed following practice. Later, pain is noticed.during the mornings, but will disappear toward the end of the day. The pain will progress to soreness and stiffness, oc- Fig. 4. Patella alta. curring during practice and interfering with activities. Sometimes, weakness or "catching" is reported. 2) Seasoned athletes or individuals engaged in lifetime fitness programs can suffer from patella malalignment syndrome as an overuse injury. As a group, they will have minimal objective pathology; however, small variations of normal alignment can lead to symptomatic complaints when the activities are highly repetitive. These individuals will often report an increase in the amount of work in their exercise program or increases in the frequency of their training prior to the onset of symptoms. 3) Patella malalignment syndrome can, in some cases, manifest itself as an acute injury. This is often seen in weekend athletes or during early season training with individuals who are unaccustomed to the intensity of their program. The pain develops rapidly under the patella during a practice session. It gets progressively worse, causing the athlete to stop histher activity. Following practice, the athlete will have moderate to severe pain, which is often reported as a burning sensation. The athlete will ambulate with the knee held rigidly in full extension since attempts to flex the knee will cause pain. STANDARD TREATMENT PROGRAMS The standard treatment for patella malalignment syndrome is conservative management,

6 KRAMER JOSPT Vol. 8, No. 6 Fig. 5. In combination, the vastus medialis and vastus lateralis produce knee extension. The vectors represent their tendency to pull the patella medially or laterally. which if unsuccessful, can be followed with surgical intervention. Standard conservative management starts with rest. (Bracing can be used if the pain is acute.) Various medications have been advocated." As the symptoms resolve, quadricep strengthening is attempted; first through isomet- f\cs, and then as to\e~ated, isotonics. (The re\a- tionship between the decrease in symptoms with increased quadricep strength is difficult to explain physiologically or biomechanically, but clinically, it appears to be related.) Patients are then allowed to return to activities as tolerated short of ~ain.~,~," In cases where conservative management fails and pain becomes a progressive problem, surgical management is indicated. Surgical management attempts to correct the biomechanical problems. Insal15 reviews the generally accepted surgical procedures which are as follows: 1) Lateral release. This is an incision through the lateral retinaculum of the patella. This procedure can be performed on its own or in combination with numerous other procedures. The goal here is to prevent a tightened retinaculum from causing the lateral deviation of the patella. 2) Proximal realignment. Proximal realignment is generally performed to create a more inferior insertion of the vastus medialis or to release some of the inferior fibers of the vastus lateralis. It is hoped that this procedure will increase the mechanical efficiency of the vastus medialis which is responsible for creating a medial tension on the patella during knee extension. 3) Distal realignment. This is the practice of changing the insertion of the infrapatella tendon by moving it in a medial direction, thus reducing the Q angle. 4) Tibial tubercle elevation. In addtion to moving the insertion of the infrapatella tendon medially, it has been found that by elevating the transplanted tubercle, this reduces the pressure on the patellofemoral groove. 5) Patellar shaving and debridement. 6) Patella replacement. 7) Excision of the patella. This should occur only in those cases where the pain is intolerable. Under these circumstances, there will be a remarkable weakness in knee extension in the last 20". All of these surgical techniques attempt to construct or reestablish the normal alignment between the patella and the femur, thus reducing the pain associated with abnormal function. CONSERVATIVE APPROACH TO REDUCE EXCESSIVE LATERAL PRESSURE It is generally accepted that regardless of the specific cause of patella malalignment syndrome, the end resub is excessive pressure on the lateral aspect of the patellofemoral articulation and damage to the hyaline cartilage. This conservative biomechanical approach attempts to reduce the lateral pressure by stretching appropriate soft tissues and to facilitate proper cartilage metabolism.

7 JOSPT December 1986 PATELLA MALALIGNMENT SYNDROME 307 Fig. 6. A, The patella is in the midline position; B, medial displacement stretching the lateral retinaculum. This management system has three general phases: Phase I. Initially, there is a short period of rest which helps to decrease the symptoms. Treatment: 1) Modality of choice. Cold packs, ultrasound, and/or high voltage Galvanic stimulation can give good relief from pain caused by inflammation. 2) Medications optional. 3) Manual therapy. The patient is sitting with the knee in full extension. Glide the patella medially and hold that position for approximately 1 minute. This is a passive forced technique which stretches the lateral retinaculum (Fig. 6). 4) Quadriceps sets with knee in full extension. In this position, the patella is above the patellofemoral articulation and should not produce pain. Phase II. The symptoms have begun to resolve. Treatment: 1) Continue with the modality of choice. 2) Medications optional. 3) Patella compression and tracking. The patient now sits with the knee flexed at 90. As the knee is extended, the patella is compressed against the patellofemoral articular surface and tracked medially (Fig. 7). Maitlandlo was the first to suggest adding compression as a treatment for intra-articular injuries. He theorized that hyaline cartilage, although avascular, contains living cells which derived their nutrition from the surrounding synovial fluid. Compressing the patellofemoral surface during knee extension appears to facilitate cartilage metabolism. Maitland's theory is supported by Salter et a1.12 who did research

8 Fig. 7. As the knee is actively extended, the patella is compressed against the patellofemoral surface with medial drift. concerning the repair of cartilage following full thickness injuries. Salter's hypothesis is that continued motion across articular surfaces facilitates the repair of this tissue. Medial tracking prevents excessive lateral pressure. 4) Isometric knee extension with knee at various angles: 90, 60, 45, and 30. The isometric contraction should not illicit patellofemoral pain. 5) Short arc extension against resistance. Have the patient flex the knee from full extension and stop at the moment of pain, pressure, or grinding. Extend the knee fully from this point. 6) Continue with quadriceps setting exercises at home. 7) The patient mobilizes the patella on his/her own. Again, the knee should be in full extension and the patient glides the patella medially. Phase Ill. Return to activities. Treatment: 1) If the symptoms continue, use a modality of choice. A soft patellar brace can be used during activities. 2) Stretch the quadriceps by placing the patient prone and produce full knee flexion, heel to but- AER JOSPT Vol. 8, No. 6 tocks. This is to ensure that minimal tightness does not increase the pressure on the patellofemoral articular surface. 3) Continue with patella compression and tracking in an active range of motion from 0-90'. 4) During the day, have the patient mobilize the patella in full knee extension. CASE STUDIES In a 6-month period, 33 patients were referred to our clinic with patella malalignment as the diagnosis, and underwent our treatment protocol. Twenty-six of these were high school and college athletes participating in sports to include soccer, field hockey, running, basketball, and skiing. All of these athletes were able to return to full activity during their competitive season. Four of these athletes stated that they continued to have occasional symptoms, but were able to manage these symptoms with the Phase Ill treatment. Of the seven nonathletes, five returned to normal activities and were asymptomatic. The two remaining had anatomical abnormalities, patella alta, and an abnormal sulcus angle, and required surgery. SUMMARY 4 Patella malalignment syndrome is a common problem among active individuals. Until now, conservative management has focused on decreasing inflammation and pain while improving strength. Surgical techniques have been developed to improve the alignment of the patella, but are expensive, have some risk, and should be used only as a last resort. It has been our experience that the treatment protocol outlined in this article for patella malalignment is an effective conservative way to treat the syndrome, decrease the symptoms, and allow the individual to continue his/her active lifestyle. REFERENCES 1. Basmajian JV: Grant's Method of Anatomy. Ed 8. Baltimore: Wilhams & Wilkins, pp , Ficat RP, Hungerford DS: Disorders of the Patello-Femoral Joint. Baltimore: Williams & Wilkins Hughston JC: Subluxation of the patella. J Bone Joint Surg (Am) 50: , Hughston JC, Walsh WM: Proximal and distal reconstruction of the extensor mechanism for patella subluxation. Clin Orthop 144:36-42, lnsall J: Current concepts review: patella pain. J Bone Joint Surg (Am) 64: , Keller EK: Patellar malalignment syndrome in runners. Nurse Pract 8:27-38, 1983

9 JOSPT December 1986 PATELLA MALALIGNMENT SYNDROME Kettelkamp DB: Current concepts review: management of patellar malalignment. J Bone Joint Surg (Am) 63: Larson RL. Cabaud HE, Sloccum DB. James SL. Keenan T, Hutchinson T: The patellar compression syndrome: surgical treatment by lateral retinacular release. Clin Orthop 134: , Luttgens E, Wells K: Klnesiology, Sc~entific Basis of Human Motion, Ed 7, pp Philadelphia: Saunders College Publ~shing Co, Maitland GD: The hypothesis of adding compression when exam- ining and treating synovial joints. J Orthop Sports Phys Ther 2: Malek MM, Mangine RE: Patellofemoral pain syndromes: a comprehensive and conservative approach. J Orthop Sports Phys Ther 2: , Salter RB, Simmonds DF, Malcolm BW, Rumble EJ, MacMichael D, Clements ND: The biological effect of continuous passive motion on the healing of full-thickness defects in articular cartilage. An experimental investigation in the rabbit. J Bone Joint Surg (Am) 62: ,1980