LUMBAR MANIPULATION AND EXERCISE IN THE MANAGEMENT OF ANTERIOR KNEE PAIN AND DIMINISHED QUADRICEPS ACTIVATION FOLLOWING ACL RECONSTRUCTION: A CASE REPORT
BACKGROUND AND PURPOSE
Quadriceps weakness following anterior cruciate ligament (ACL) reconstruction is a common clinical finding that can be functionally limiting and return to pre‐injury status can be difficult. Approximately 100,000 to 130,000 ACL reconstructions are performed each year,1—3 the majority of which follow non‐contact injuries.2 In order to return to high levels of activity, many individuals opt for surgical reconstruction following ACL injuries. Impaired quadriceps strength that is <85% of the uninvolved side has been correlated with functional impairments.4 Patients with <80% quadriceps strength demonstrate similar gait mechanics to patients with ACL deficient knees, while patients with >90% quadriceps strength demonstrate gait mechanics similar to a normal population.5 These findings highlight the importance of maximizing quadriceps recruitment in order to optimize physical function after injury or surgery.
Quadriceps weakness in this population may be a sign of centrally mediated inhibition. In fact, altered spinal and supraspinal excitability has been hypothesized to impair volitional quadriceps activation, thus contributing to quadriceps weakness.6,7 The flexor withdrawal reflex (FWR), also called the nociceptive reflex, has been utilized experimentally to demonstrate central sensitization of nociceptive pathways in individuals with musculoskeletal dysfunction, including ACL rupture.7 Accordingly, central sensitization may occur following repetitive or a single musculoskeletal trauma8 such as ACL rupture. With hyperexcitability of the FWR, not only is hamstring activation (flexors) triggered, but also quadriceps activation may be inhibited. Thus, central sensitization of nociceptive pathways may promote inhibition of quadriceps activation. Hyperexcitability of this reflex has been demonstrated in an animal model of knee joint injury9,10 and in patient populations with musculoskeletal dysfunction.11—14 However, quadriceps inhibition has not been closely associated with hyperexcitable pain mechanisms when examined in persons with knee OA,11 indicating that the relationship between altered quadriceps activation and central pain mechanisms may require further research.
Joint mobilization has been utilized clinically to increase range of motion and decrease pain.15 Recent studies have demonstrated that thrust16 and non‐thrust17 manipulation functions in part, by decreasing central nociceptive excitability. In addition, previous authors have reported improved quadriceps muscle activation and decreased knee pain immediately following application of sacroiliac or lumbopelvic joint thrust manipulations in individuals with anterior knee pain/patellofemoral pain syndrome (PFPS).18—22 Spinal joint mobilization/manipulation stimulates sensory receptors within and around the joints23 and this input to the central nervous system may affect motoneuron pool availability and efferent motor output at the involved segmental levels.24 It has been suggested that because the sacroiliac joint (L2‐S3), quadriceps (L2‐4) and knee joint (L2‐S2) share common nerve root levels,25 sensory input from the treatment of one structure, such as the lumbar spine, may alter motor output to structures sharing the same nerve root innervations (such as the quadriceps muscle).26 However, previous studies examining this premise have utilized a supine lumbopelvic or sacroiliac joint manipulation.
The purpose of this report is to describe the physical therapy management of anterior knee pain and chronic quadriceps weakness utilizing side‐lying rotational lumbar thrust manipulation and therapeutic exercise for an individual eight months status‐post ACL reconstruction.
CASE DESCRIPTION
History
A 20 year‐old male college student presented to a university physical therapy clinic following ACL reconstruction of the left knee using an allograft eight months prior, following an isolated ACL tear, sustained while playing basketball. His chief complaint was left anterior knee pain and weakness for the previous five months, with insidious onset. The subject had two episodes of physical therapy prior to this evaluation: one bout following surgery and another at approximately five months post‐op. The subject reported ongoing quadriceps weakness following the initial course of care. Prior to initiating the second course of care, the subject reported performing a HEP three times each week, including straight leg raises in four different directions, and calf stretching. When communicating with the subject's second physical therapist, the author found that the subject's quadriceps strength was 3+/5, as measured with manual muscle testing (MMT), at the onset of the bout of therapy. The second episode of care focused on improving quadriceps strength and dynamic stability through a combination of open and closed kinetic chain strengthening, dynamic balance exercises, and neuromuscular electrical stimulation for strengthening. Unfortunately, the subject's second therapist noted that the subject continued to experience left anterior knee pain and significant weakness, which limited performance of recreational and sports related activities. Further information related to the prior episodes of care can be seen in Table 1.
The subject's pain was aggravated with descending stairs and using the leg extension machine at the gym. Transient, sharp pain was reported as 7/10 on the numeric pain rating scale (NPRS) with these activities; however decreased with cessation of the aggravating activities (pain at rest reported from 0‐2/10). No complaints of low back, hip, or foot/ankle pain were reported. He noted no swelling, sensations of clicking, catching or instability. No other significant orthopedic injuries or past medical history was reported. The subject's primary goals were to decrease pain, increase strength, and return to recreational soccer and basketball. The referring surgeon stated that there were no precautions, and he expected return to recreational sport at nine months for most of his ACL reconstruction patients.
Clinical Impression I
The primary author hypothesized that the subject's ongoing symptoms appeared consistent with PFPS. The pain was localized to the anterior aspect of the knee, was mechanical in nature (worse with lifting weights and descending stairs), and did not refer proximally or distally. Neurological symptoms were not reported. Based on the subject's pain location, other potential diagnoses on the therapist's differential list included lumbar or hip joint pain referral, patellar tendinopathy, fat pad or plica syndrome, or meniscal pathology.
Based upon the subject's report and communication with his previous physical therapist, the subject appeared to have followed a typical post‐ACL reconstruction protocol. However, no manual therapy beyond patellar mobilization was utilized in either course of therapy. Manual therapy directed to the lower quarter in addition to stabilization exercises and other interventions has been reported to be beneficial in decreasing pain and improving function a small sample of subjects with PFPS.27 Additionally, multiple studies have reported thrust manipulation directed towards the lumbopelvic region may be beneficial at decreasing pain and improving quadriceps recruitment.18—22 Based on the ongoing impairments following interventions primarily utilizing exercise and modalities, the therapist hypothesized the addition of manual therapy could facilitate improved outcomes for this subject, potentially by modulating centrally mediated muscle inhibition.
EXAMINATION
While local knee joint examination was the main priority, proximal and distal joint screening was also performed. The therapist evaluated the lumbar spine, hip, and talocrural joints for impairments that could potentially contribute to the subject's symptoms. Standing examination, including functional testing, was performed prior to tests done on the plinth, in order to improve examination efficiency.
Active range of motion (AROM) of the lumbar spine with overpressure demonstrated full ROM and did not reproduce any symptoms. A bilateral squat was performed, with increased weight bearing noted on the right side, without reproduction of symptoms. With unilateral squat, femoral adduction and internal rotation was noted on the left along with an anterior trunk lean (a compensatory pattern often utilized in the presence of quadriceps weakness), with hesitation noted with increased knee flexion. No impairment was found on the right. Similar hesitation and loading patterns were noted with a single leg sit to stand test (an accurate functional assessment of quadriceps strength)28 and a step down test. Pain was noted during the step down test at 47° left knee flexion. Hop testing was performed on the right; however the subject declined to perform this testing on the left secondary to hesitation and fear of re‐injury. A neurologic screen assessing lower quarter myotomes, light touch sensation in a dermatomal pattern, and lower quarter reflexes was normal.
Quadriceps force was objectively measured using a MicroFET 2 (Hoggan Health Industries, Inc., Drapper, UT) hand‐held dynamometer with the subject sitting at the side of the treatment table with the leg tested at 90° of knee flexion (Figure 1). A break test was performed in this position over the course of five seconds. The mean of three trials was recorded on each leg, with the right scoring 101.6 lbs and the left scoring 70.6 lbs. Testing the left side increased pain to 7/10 which immediately decreased to 1/10 with cessation of the test.
Strength testing on the left revealed additional impairments of the hip abductors and hip extensors (tested with the knee flexed), which both measured as 4/5 using MMT in sidelying and prone, respectively. No lower quarter flexibility or neural tension impairments were observed with the straight leg raise (SLR) or Ely test. When assessing joint mobility, no hip, talocrural or subtalar joint restrictions were noted. However, mild restriction was noted with an inferior glide of the left patella. Ligamentous stability testing of the left knee was negative, making apprehension during dynamic tasks less likely the result of true knee instability. Palpation revealed tenderness at the medial facet of the left patella, reported as 3/10. No tibiofemoral joint line or patellar tendon tenderness was noted.
Outcomes were measured using the Lower Extremity Functional Scale (LEFS), NPRS, hop testing, and quadriceps force generation (as measured by HHD). The LEFS is a validated outcome measure of self‐reported function with 20 questions answered on a scale of 0 (extreme difficulty) to 4 (no difficulty), with higher scores representing higher levels of function. The minimal clinically important difference (MCID) is 9 points29 and was shown to have high test‐retest reliability in subjects with anterior knee pain.30 Hop testing after ACL reconstruction is a commonly used functional performance test, often one criteria for assessment for return to sports, and has been shown to be valid and reliable.31 HHD and MMT have both demonstrated convergent construct validity in measuring knee extensor strength, however the discriminant construct validity of MMT has been challenged.32
Clinical Impression II
Following the examination, patellofemoral pain syndrome appeared to be the most likely diagnosis. This was supported by tenderness along the medial patellar facet, and reproduction of pain with resisted concentric and eccentric quadriceps contractions (when the patellofemoral joint space is compressed). It appeared that residual quadriceps weakness, decreased hip strength, and decreased confidence and altered mechanics in single leg activities were contributing factors to the subject's anterior knee pain. Lumbar, hip, ankle and neurological screens were negative, making a referred pathology less likely. No tenderness was present at the patellar tendon, medial plica, or fat pad. Additionally, when coupled with the subject's denial of swelling, clicking or catching, and the lack of joint line tenderness, meniscal pathology seemed unlikely. When reviewing the operative report, no meniscal, cartilage or other soft tissue injury had been noted.
Previous investigations of asymptomatic individuals and those with anterior knee pain have shown small, but statistically significant, short‐term improvements in quadriceps output and decreased pain following lumbopelvic or sacroiliac joint manipulation.18—22 Spinal manipulation has a number of proposed neurophysiological effects, including dampening of central inhibition and altering motoneuron excitability, which is potentially why improved efferent motor activity can be noted immediately afterwards.23 Because prior interventions had not yet returned the subject back to sports, and given the results of previous studies, the therapist believed lumbar thrust manipulation may aid in the subject's recovery. By temporarily improving quadriceps force generation, the subject would ideally be able to perform other activities with improved muscle activation patterns and without sagittal plane compensation. No contraindications preventing the utilization of thrust manipulation were noted.
INTERVENTION
The primary goal of physical therapy intervention was to increase left lower quarter strength and decrease knee pain, in order to facilitate the subject's return to his prior level of function. To accomplish this, primary interventions used were a side‐lying rotational lumbar thrust manipulation, followed by dynamic balance exercises, progressive concentric and eccentric quadriceps loading exercises, and hip abductor and extensor strengthening. Eccentric exercise appears to be a safe and effective method of increasing quadriceps strength in individuals status post ACL reconstruction.33—35 The combination of these exercises had been utilized with this subject previously, however no manual therapy interventions were previously performed at proximal segments.
Initial Evaluation
Following the initial evaluation the subject was educated with a home exercise program (HEP) including weight training for the quadriceps in a pain free range of motion, as pain can have an inhibitory effect of quadriceps output.36,37 The subject was already performing lower quarter strengthening in the gym four times each week (leg press, leg extension, leg curls, squats). Single leg sit to stands were prescribed for daily performance, with instruction to control the lowering phase facilitating unilateral eccentric loading of the knee. The subject was instructed to slowly lower himself from standing using the left leg only to a surface where the range of motion remained pain free. As the exercise became easier, the surface height was lowered to facilitate control through a greater range. The subject was also educated to avoid using the leg extension machine as it exacerbated symptoms.
Visit 2, Week 2
The subject reported symptoms remained unchanged at the first follow up visit. Following re‐assessment, a five‐minute self‐selected pace warm up on a bike without added resistance was performed. Afterwards, lumbar manipulation as described by Cleland et al38 was directed at the L3 segment, with the subject in right side‐lying, as the left was the symptomatic extremity (Figure 2). Knee extension force was measured with a hand‐held dynamometer before and after the thrust technique. Baseline quadriceps strength was 73.2 lbs, which increased to 78.8 lbs immediately following the lumbar manipulation treatment. The subject then performed a series of exercises combining both dynamic balance and strength training of the left knee extensors as well as the left hip abductors and extensors. These included single leg mini squats in a mirror in order to facilitate knee position awareness as well as eccentric quadriceps loading, decline squats (Figure 3) to increase quadriceps recruitment, single leg deadlifts to increase gluteal strength and stability in single leg stance, and walking lunges to facilitate quadriceps recruitment as well as lumbopelvic stability. Bilateral squats on a BOSU® ball (Figure 4) were performed with cues to keep the platform parallel to the ground, in order to encourage equal weight bearing and balance. The subject's HEP was modified to primarily focus on the eccentric phase of squats and leg press in order to increase quadriceps loading. Additionally, the patient was educated to attempt to control sagittal plane motion at the knee complex during exercises. The details of the subject's exercise program can be seen in Table 2.
Side‐lying rotational lumbar thrust manipulation. (a). The therapist passively flexes the patient's legs until movement is felt at the L3‐4 interspinous space. (b). The therapist then grasps the patient's bottom shoulder and introduces ...
BOSU® ball squat. (a). Starting position, (b). While squatting, the patient attempts to keep the platform parallel to the ground
Visit 3, Week 3
At the following visit, the subject reported improvements in pain (5/10 at worst, with no pain at rest). The next two visits were similar in regards to interventions. A warm up at a similar pace preceded right side‐lying rotational lumbar thrust manipulation targeted at the L3 segment with quadriceps force measured pre‐ and post‐treatment (Table 3). The subject performed the same exercises but with more repetitions for improved endurance and enhanced motor control. The depth of squats was increased with proper form, and the subject reported increased confidence in single leg activities.
Visit 4, Week 4
At the fourth follow up visit, the subject continued to report pain with aggravating activities, but with decreased intensity (3/10 at worst). The subject also reported subjective improvements in knee strength, but still felt limited with sports. Lumbar manipulation was again performed with strength improvement (Table 3), followed by therapeutic exercises. Based on good technique noted with exercises on level surfaces, single leg squats and deadlifts were performed on a half foam roll to add a challenge to the subject's balance (Figures 5 & 6). Jump landing training was initiated with the subject jumping off both feet, and landing on both feet, focusing on equal loading. As this became easier to perform, the subject began jumping off a step and landing on both legs to increase loading demand.
Visits 5‐8, Weeks 5‐8
At subsequent follow up visits the subject continued to report improvements in left knee strength and pain (Table 3). He was able to participate in recreational basketball with friends, primarily non‐competitive games, although felt limited with anything more than jogging. Lumbar manipulation was performed at the onset of follow up visits by the same therapist, followed by progressive strengthening and dynamic loading of the quadriceps. Plyometrics were advanced to increase quadriceps demand and to make therapeutic exercise more sport specific. Specifically, double leg jumps for height and for distance were performed, and when good technique was demonstrated, speed of performance was increased. Also, the subject performed single leg jumps to replicate lay‐ups, demonstrating good form and no complaints of instability.
OUTCOMES
The subject was seen for eight total sessions (including the initial evaluation) over the course of 8 weeks. At each follow up visit the subject consistently reported improvements in pain and function, with quadriceps force production improvements demonstrated using HHD (Table 3). At the eighth visit the subject performed hop testing, which was measured at 92% of the unaffected lower extremity indicating high function.4 Lower extremity functional scale scores had improved from 58/80 to 72/80 satisfying the MCID of nine scale points, indicating a clinically significant improvement in self‐reported function. The subject did not report pain with previously aggravating activities, and was able to play recreational basketball without complaints. The subject was discharged with an updated HEP for continued functional improvement. Outcome measures at initial evaluation, four weeks and eight weeks can be seen in (Table 4). In a follow up email received three months following discharge, the subject reported that he had fully returned to playing basketball and soccer without discomfort.
DISCUSSION
Quadriceps weakness is a common impairment found in individuals following ACL reconstruction. Months and even years after surgery, individuals status‐post ACL reconstruction may exhibit impairments in strength and function.39—45 Quadriceps weakness can be functionally limiting, particularly in individuals hoping to return to sports. Recent evidence has suggested that central mechanisms may play a role in this dysfunction.9,11,13,16,17,26,46—48 While some studies have attempted to identify the mechanisms underlying quadriceps inhibition,24,48 less is known regarding the optimal methods to maximize quadriceps strength in order to improve function.
Altered muscle activation patterns in the lower extremity have been reported in individuals following ACL rupture,9 and hyperexcitable FWR reflex activation has been demonstrated,47 indicating central changes in nociceptive processing in this population. It follows that quadriceps inhibition could be associated with this heightened reflex, however this has not been demonstrated in previous studies, nor has it been examined following reconstructive surgery. Future studies in subjects following ACL reconstruction, utilizing a combination of methods such as FWR threshold or temporal summation (which both examine excitability of nociceptive pathways),11,16 conditioned pain modulation protocols (which examine descending inhibitory mechanisms),49 in conjunction with quadriceps burst superimposition (which examines central activation failure of the quadriceps),11 may advance understanding of potential mechanisms underlying quadriceps dysfunction.
Joint mobilization and manipulation have been demonstrated to decrease central nociceptive excitability,16,17as well as promote positive clinical outcomes.50 Supine thrust manipulation to the lumbosacral spine has previously been associated with small improvements in quadriceps output in both the symptomatic and asymptomatic population and decreased knee pain for subjects with PFPS18—22 while the effects of a side‐lying rotational thrust lumbar manipulation in a similar patient population have not yet been investigated. Some studies utilizing thrust manipulation suggest that the effects of either technique may be similar.38 In this case, an individual with an isolated ACL reconstruction with residual anterior knee pain and quadriceps weakness demonstrated improvement in pain and function over eight visits with a treatment plan including side‐lying rotational lumbar thrust manipulation and exercise. While improvements in muscular force output of the quadriceps were seen immediately after the application of thrust manipulation, it was interesting to see that between session improvements also occurred. Not only did quadriceps strength, as tested using HHD, consistently improve, but more importantly the subject's functional level improved both in functional performance and patient self‐report measures. Most notably, the subject was able to return to sports with increased confidence in dynamic use of his involved limb. However, this could potentially be related more to the exercise component of the therapy program (which was performed between sessions), or by simply removing a painful activity, the leg extension machine, which could have an inhibitory effect on muscle output by continuing patellofemoral irritation.
A number of limitations exist within this case report. While the premise that lumbar manipulation may have effect on ACL reconstruction related quadriceps weakness is alluring, it is impossible to make conclusions as such from a case report. Further study on the mechanisms underlying ACL injury related quadriceps weakness and the treatment of this impairment would be beneficial. There is inherent measurement error with HHD considering the test is based on voluntary effort. In the presence of pain, subjects may have apprehension leading to submaximal output. Expectation for improvement after intervention is also a possibility, introducing potential bias related to subject performance. Also, improvements in quadriceps output values may be related to an order effect, as the measurements were not taken at any other time during the course of care. Given the potential drawbacks to the measurement techniques, readers are advised to examine the results with caution. Similarly, a number of interventions were used in addition to lumbar thrust manipulation. Exercises concentrically and eccentrically targeting the gluteal region, quadriceps, and hamstrings, in addition to dynamic stability exercises were used. Although the subject presented with impairments indicating the need for this particular exercise prescription, it becomes challenging to determine the effects of thrust manipulation in isolation, and therefore, improvement must be attributed to the combined care offered to this subject. Additionally, objective or patient reported measures of apprehension and potential kinesiophobia were not gathered. Although subject education informally addressed the subject's fears, objective data would have been more beneficial in not only measuring the impact but potentially focusing treatment.
CONCLUSIONS
In cases of anterior knee pain and lower extremity weakness that do not respond to traditional interventions, other interventions should be considered. In patients status‐post ACL reconstruction, the side‐lying rotational lumbar thrust manipulation appears to be a safe intervention that may facilitate increased quadriceps muscle activity without putting undue stress on the healing ACL graft, when used in conjunction with therapeutic exercise. Future research could be performed to determine if subjects receiving lumbar manipulations demonstrate improved quadriceps output or achieve quadriceps strength milestones more rapidly than those who do not receive manipulation. Because the side‐lying technique is applied to the lumbar spine, it may be safe for patients status‐post ACL reconstruction once they have enough knee flexion ROM to attain the treatment position. Additionally, future studies could compare the effects of side‐lying and supine thrust manipulation on anterior knee pain and quadriceps function.
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