Piriformis syndrome is a commonly overlooked diagnosis for hip and buttock pain. In the article, Diagnosis and Management of Piriformis Syndrome: An Osteopathic Approach, the researchers reviewed the literature to present a summary of this diagnosis as well as a variety of treatment options.

This diagnosis is a neuromuscular condition which is caused by peripheral neuritis of the sciatic nerve due to an abnormal condition of the piriformis muscle. It is characterized by hip and buttock pain, parasthesia, hyperasthesia, and muscle weakness. This syndrome occurs most frequently in women ages 40-60. Incidence ranges widely from an estimated 5% to 36% among patients with low back pain.

The sciatic nerve exits inferior to the piriformis in the majority of the population. It is estimated that in 22% of the population, the sciatic nerve pierces the muscle, splits the muscle, or both as it travels posteriorly down the leg. When this anatomical variation is present, it is known as primary piriformis syndrome.

Secondary piriformis syndrome occurs as the result of a micro or microtrauma, local ischemia, or mass ischemia. The most common cause is a direct trauma to the buttocks region, leading to inflammation of soft tissue and/or muscle spasm which results in nerve compression. Microtrauma may result from overuse of the muscle such as in long distance walking or running.

The most common symptoms patients present with include increased pain while sitting longer than 20 minutes and tenderness over the piriformis muscle. Patients might also complain of difficulty walking and pain while sitting cross-legged. The symptoms may appear gradually or suddenly and are associated with spasm of the muscle or compression of the sciatic nerve.

As clinicians, we also look for certain objective measures to support the diagnosis including tenderness to palpation of the piriformis, palpable mass in the muscle belly, weakness, limited hip internal rotation of affected side, and a shorter leg on the affected side. A spasming piriformis muscle causes ipsilateral hip external rotation, anterior sacral torsion toward ipsilateral side, and compensatory lumbar rotation in the direction of the spasming side. Additional osteopathic tests include the Pace sign, Lasegue sign, Freidberg sign, Beatty test, and FAIR test (flexion, adduction, internal rotation). Differential diagnoses include lumbosacral radiculopathy, degenerative disc disease, compression fractures, and spinal stenosis. The obturator internus muscle has also been suggested as a contributing source of sciatic neuritis in patients with piriformis syndrome.

Physical therapy is a great option to treat patients with piriformis syndrome. A trained physical therapist will focus on treatment techniques specific to this diagnosis which focus on decreasing and eliminating the spasm in the piriformis by way of strain-counterstrain and facilitated positional release. Spinal, pelvic, and hip manipulations might also be warranted to address associated lumbo-pelvic dysfunctions. Strengthening of the hip adductor muscles has been shown to be beneficial for this syndrome as well as a stretching sequence which is tailored to each patients’ needs. The staff at Physical Therapy First are board-certified manual trained therapists with experience providing these techniques. Further diagnostic tests and imaging include EMG studies, and MRI or CT scan to rule out lumbar disc pathologies. Other treatment includes pharmacologic treatment (NSAIDs, muscle relaxers, local steroid injection, and prolotherapy), and in severe cases, surgery.

Reference

Boyajian-O’Neil, L., McClain, R., Coleman, M., Thomas, P (2008). Diagnosis and Management of Piriformis Syndrome: An Osteopathic Approach. Journal of the American Osteopathic Association: Volume 8, No 11.

INTRODUCTION
Spinal Manipulative Therapy (SMT) is known to help decrease pain and improve spinal mobility. The authors of this article, Effect of Spinal Manipulative Therapy with Stretching Alone on Full-Swing Performance of Golf Players, propose that this treatment also coincides with maintenance and improvement of joint function, muscle balance and speed of neuromuscular reflexes, thus optimizing an athlete’s performance in their sport.
A golfer’s swing is a complex full-body motion which requires spinal mobility and limb flexibility. The shoulders are required to rotate up to 90 degrees and the hips by 45 degrees. This rotation places higher compressive loads in the low back (8x body weight) than rowing (7x) or running (3x). Because of this increased force on the spine, muscle strains are a common injury amongst golfers.
The researchers in this article evaluated the effect of SMT on the performance of golf players with a handicap between 0-15 during their full swing using a driver club.

METHODS
Men between the ages of 18 and 55 with a handicap from 0 to 15 and who practiced golf at least once a week for four hours were recruited from two golf clubs in Brazil. They were randomly selected to be in one of two groups: Group I was a stretch-only program and Group II was a stretch and SMT program.
The stretches performed by both groups included those for the forearm flexors, deltoids, brachioradialii, biceps, forearm extensors, levator scapulae, gastrocnemii, solei, quadriceps, hamstrings, and gluteal muscles which were performed bilaterally for 20 seconds. Each golfer was also evaluated for joint dysfunction in the cervical, thoracic, and lumbar spine. SMT was performed on the dysfunctional segments in participants in Group II only.
Prior to each treatment, the participants performed three full-swing shots and the average distance of the shots was recorded. Participants then participated in the intervention (stretching or stretching + SMT) and performed three more full-swing shots on the driving range. This process was repeated once weekly, for a total of four weeks.

RESULTS
Group II showed a gradual improvement in the pre to post intervention shot distances across the four days, as seen in Figure 1 below. The fourth and final day showed a statistically significant change between pre and post intervention. When looking at Group I’s pre to post intervention distances, the results were inconsistent, as seen in Figure 3 below. There was a statistically significant decrease in average pre to post shot distance on day two.

Figures 2 and 4 below compare the shot averages between the first and last days of the experiments in Groups II and I, respectively. There were improvements in both groups, but neither was of statistical significance.

LIMITATIONS
This study has a small sample size (43 men) and is not representative of all golfers, including the estimated 80 million female golfers worldwide, according to the National Golf Foundation.

CONCLUSIONS
The authors concluded that stretching and SMT seemed to be associated with an improvement in golfer’s swing performance. Therefore, spinal manipulative therapy could be a treatment option for patients who enjoy golfing.
Clinical Significance
Our clinicians have extensive training in manual therapy and efficiently evaluate and assess our patients to ensure they are appropriate candidates for safe manipulation techniques. Assessment of spinal mobility in the cervical, thoracic and lumbar spine, extremity joint mobility, soft tissue flexibility and strength are considered and evaluated as all are important for a successful golf swing. Come see us for an initial evaluation and treatment session to get ready for your upcoming golf season!

REFERENCE:
Costa, S., Chibana, Y., Giavarotti, L., Compagnoni, D., Shiono, A., Satie, J.: Bracher, E (2009). Effect of spinal manipulative therapy with stretching compared with stretching alone on full-swing performance of golf players: a randomized pilot trial. Journal of Chiropractic Medicine 8: 165-170.

A COMPARISON OF TWO NON-THRUST MOBILIZATION TECHNIQUES APPLIED TO THE C7 SEGMENT IN PATIENTS WITH RESTRICTED AND PAINFUL CERVICAL ROTATION
Mobilizations and manipulations to joints in the cervical spine is a common intervention performed by physical therapists to improve neck range of motion. There is controversy about using rotary thrust manipulations in the lower cervical spine and has potential to cause adverse reactions, therefore it may be more appropriate to use non-thrust mobilization techniques instead. A study looked at the effectiveness of two different types of non-thrust mobilization techniques. These 2 techniques are:

Non-thrust C7 facet joint gliding mobilization: (for restricted right rotation): “The T1 segment is manually stabilized in left rotation by pressing the left shoulder girdle in a posterior direction. Bilateral translatory movements are applied to the lamina and inferior facets of the C7 segment in the direction of right rotation.” (Left image below)
Non-thrust facet joint distraction mobilization: (for restricted right rotation): “The clinician uses his left hand to separate (distract) the right inferior facet of C7 away from the superior facet of T1. The clinician uses his right hand to maintain a ventral and medial pressure against the lamina and inferior facet of C7. This compresses the inferior facet of C7 against the superior facet of T1. This will shift the axis of movement to the left, which will facilitate greater motion (facet distraction) on the right side of the C7 segment. Manual stabilization of the T1 segment occurs by using the right lower extremity to passively press the left shoulder girdle and clavicle in a posterior direction, which rotates the T1 segment in the opposite direction of the intended mobilization.” (Right image below)
**In this study, one intervention = three consecutive, 7-second, grade III, non-thrust facet glide or facet distraction mobilizations**

Creighton, D., Gruca, M., Marsh, D. and Murphy, N., 2014. A comparison of two non-thrust mobilization techniques applied to the C7 segment in patients with restricted and painful cervical rotation. Journal of Manual & Manipulative Therapy, 22(4), pp.206-212.

This study had 30 participants who had cervical pain rated as 2/10 or higher, pain with both left and right active cervical rotation, and limited active cervical rotation in both directions when measured with a CROM. The participants were split in half in which one group received the facet joint glide technique and the other received the facet joint distraction technique.

Outcomes measured for this study were degrees of active right and left rotation, pain rating at end range right and left cervical rotation, and the number of adverse reactions produced. These measures were taken before and after the mobilization technique was performed.

The results display that both groups of participants had a statistically significant increase in both right and left active cervical rotation range of motion: about 5 degrees increase in both directions. There was also a statistically significant decrease in pain levels for both right and left active cervical rotation. No adverse reactions were reported by any subject. One technique did not produce significantly better results compared to the other technique.

Limitations of this study include: the researcher was not blinded, challenging study reproducibility since training is likely required to perform the same techniques, possible placebo affect may have occurred, small sample size, possibility for measurement error, and does not look at long term outcomes.

Despite the limitations, these 2 techniques show that they can be a safe, low risk, and effective addition to a treatment session for patients with limited and painful cervical rotation range of motion. However, these techniques do not prove to be a stand alone way to improve cervical pain and range of motion. It is recommended that therapeutic exercise and other manual therapy interventions should be performed in addition to these techniques to have the best outcomes.

Reference:

Creighton, D., Gruca, M., Marsh, D. and Murphy, N., 2014. A comparison of two non-thrust mobilization techniques applied to the C7 segment in patients with restricted and painful cervical rotation. Journal of Manual & Manipulative Therapy, 22(4), pp.206-212.

Knee osteoarthritis (OA) can lead to decreased functional performance due to the common symptoms of knee pain, stiffness, muscle weakness, and impaired balance. Included in the current best practice for treatment of knee OA includes exercise prescription to increase mobility and physical activity tolerance. Exercise has been shown to decrease pain and improve overall function in patients with knee OA.

A recent randomized controlled trial by Ylmaz et al. compared the effectiveness of a home exercise program (HEP) and a home exercise program taught by a physical therapist in patients with knee OA. One group of patients with knee OA received a HEP in a brochure and the second group received a HEP taught by a physical therapist. Both groups completed the same exercises for 6 weeks. The authors wanted to see if there would be a difference between pain reduction, range of motion, strength, and physical functioning between groups.

Exercises Performed

The following exercises were performed daily for 6 weeks, 2 times per day, for 15 repititions:

• Isometric contractions of quadriceps, hip adductors, and hip abductors
• Straight leg raises
• Hip adductor and abduction
• Knee flexion and extension
• Terminal knee extension
• Knee flexion and extension with 1 kg

Results:

The results of the study found that both groups had improvements in pain, range of motion, muscle strength, and physical functioning following the completion of their HEPs. However, the group who was instructed in their HEP by a physical therapist had statistically significant decreases in pain, increases in knee range of motion, and increased physical functioning when compared to the group who received a HEP through a brochure.

What does this mean for you?

First off performing a HEP is beneficial in both a brochure format and when taught by a physical therapist. However, it is more beneficial for pain and physical functioning when instructed by a physical therapist. This article demonstrates the importance of completing HEPs prescribed by a physical therapist and the benefit of completing exercises at home. If you are having trouble completing your activities of daily living due to knee OA Physical Therapy First can create a personalized exercise program to get you back to your favorite activities.

Ylmaz M, Sahin M, Algun ZC. Comparison of effectiveness of the home exercise program and the home exercise program taught by physiotherapist in knee osteoarthritis. J Back Musculoskelet. 2019;32:161-169.

by John A. Baur, PT, DPT, OCS, CSCS, FAAOMPT

Frobell et al BMJ 2013 findings in a 5-year report shows that there was no difference in any outcome between those who were operated on straight away, those who were operated on later and those who did not have an operation at all. The message to the medical experts who are treating young, active patients with ACL injuries is that it may be better to start by considering physical therapy first rather than operating right away.

Does physical therapy first make a difference?

Eitzen et al JOSPT found in a 5-week progressive exercise therapy program (twice a week for 10 sessions) in the early stage after ACL injury, after a quiet knee, led to significant improved knee function before the decision making for reconstructive ACL surgery or further nonoperative management. The compliance to and tolerance for the program was high, with few adverse events.

A quiet knee is a knee that has full AROM (or almost full), has little swelling if any, has no quads lag and has little pain.

In a study conducted by the University of Delaware and Norway (Delaware-Oslo Cohort) which was funded by NIH and Norwegian National Institute of Health, 300 patients followed prospectively, 150 patients at each location (Delaware and Oslo, Norway). Patient were undergone orthopedic screening, 10 sessions of perturbation, functional testing, surgery or no surgery, 6 month / 1 year / 5 year follow up.
The differential response (those people who feel stable after the injury) to ACL injury can be affected by physical therapy. As physical therapy continues over a 3-month period, stability strategies change. A month-long stability program can substantially change the patients preoperatively to have their knees be stable. As physical therapy continues from the whole period from the injury/acute stage, to subacute (quiet knee) to surgery the patient progresses stability strategies change and the categories are fluid.

Noncopers can become more stable and potential copers can become unstable. Noncopers are patients who are unable to perform functional activities and have repetitive episodes of the knee “giving-way” or instability. These noncopers are less likely candidates for non-operative treatment.

While surgery introduces passive stability, successful outcomes is not inevitable. Patients intent to return to previous level of activity is not a predictor of actual return to play. So, for example, those who intent to undergo surgery because they intend to return to play or those who choose not to undergo surgery because they do not intend to return to play have been found to return to roughly the same outcome level after one year whether they intended to return to play or not.

In the Delaware-Oslo ACL Cohort, each group found that almost one-third of the patients with ACL ruptures did not need to undergo ACL reconstruction surgery and two-thirds did undergo ACL reconstruction surgery.

In Grindem et al BJSM 2014 study Delaware-Oslo ACL Cohort showed superior 2-year patient-reported outcomes compared with the usual care of Norwegian Knee Ligament Registry (NKLR). In 86-94% of the ACL reconstructive patients who underwent progressive preoperative and post-operative physical therapy at the sports medicine clinic had 2-year postoperative patient-reported outcomes (IKDC) comparable to the general population without knee injury.

Is a quiet knee enough to return to play? No

Does delaying surgery seem to help, hurt or make no difference? Delaying surgery seems to help outcomes after an ACL rupture.

In Grindem et al (BJSM 2016) found the risk of reinjury was reduced by 58% for each month return to sport (RTS) was delayed until 9-months after surgery. Only 5.6% of patients who pass the RTS criteria before returning to level I sports suffer reinjuries compared to 37.5% of those who didn’t pass. In addition, more symmetrical quadriceps strength prior to return to sport was an independent reducer of risk of knee reinjury. Those who returned to level I sports had a 4.68-times higher risk of knee reinjury than those who did not. Using simple decision rules could reduce reinjury by 84%.

Treatment Recommendations

– Treatment to decrease knee joint effusion early such as, cold, compression, elevation and active motion.
– Stretching, patellar mobilization and quadricep strengthening to restore and preserve passive and active knee extension.
– Increase / maintain quadriceps strength should include progressive exercise and neuromuscular reeducation electrical stimulation.
– Restore normal movement patterns/gait – Neuromuscular training with at least 4 session of perturbation training)
– Short-term progressive exercise therapy programs should be incorporated in the early stage after ACL injury, to optimize knee function as a first step in the preparation to return to previous activity (or not) with or without surgery.
– Physical therapy should incorporate exercise and postures for secondary prevention.

Secondary Injury prevention Exercise may include:

– Nordic Hamstring Curls
– Standing squats
– Drop jumps
– Triple single-leg hops
– Tuck jumps

Can individuals return to sports after ACL injury without ACL reconstruction surgery?
YES

Why consider non-operative management?
– Some patients may wish to delay or avoid surgery
– Different practice patterns in different parts of the world
– Surgical reconstruction and return to sports activities are not an effective strategy for preventing early onset of knee OA.
– Not all patients need to have reconstructive surgery.

Management Algorithm Criteria

No physical impairments
– No Knee joint effusion
– Full knee active / passive range of motion
– ≥70% Quadriceps strength
– Able to hop on injured leg without pain
ACL Screening
– Hop Testing
o Single hop
o Triple cross-over hop
o Triple hop
o Timed hop (≥80%)
– KOS(≥80%)
– Global rating (≥60%)
– Number of giving way episodes (≤1)

Grindem et al (JBJS 2014) conducted a study on nonsurgical or surgical treatment of ACL injuries: knee function, sports participation and knee reinjury

Nonsurgical and surgical ACL outcomes were studied with different levels of sports. The study described categorized sport in the following levels:
Level 3 sports = Cross-country skiing, running, cycling, swimming, strength training Level 2 sports = Volleyball, martial arts, gymnastics, ice hockey, tennis/squash, alpine/telemark skiing, snowboarding, dancing/aerobics
Level 1 sports = Handball, soccer, basketball, floorball which involve running, pivoting, jumping, cutting

Almost 100% of nonsurgical patients return to level 3 sports/activities, about 60% return to level 2 sports and approximately 20% return to level 1 sports. In the operative patients almost 100% of patients return to level 1 sports.

More patients who participate in level 2 sports elected nonoperative management and more patients participating in level 1 sports elected operative management. Approximately all patients returned to the reinjury activity levels at about the same percentage.

Should individuals return to sports after ACL injury even if they have reconstruction surgery?
If our goal is long term knee health than maybe not.

At Physical Therapy First we believe that providing true sport physical therapy requires a physical therapist who is “evidence informed and clinically astute”. Physical Therapy First works hard to stay well-informed with the best and latest true sports physical therapy research and our residency / fellowship trained physical therapist are clinically skilled and astute. We believe this makes a true difference in our patient physical outcomes and successful return to sports.

References

Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med 2016; 50:804–808.

Grindem H, Eitzen I, Engebretsen L, Snyder-Mackler L, Risberg MA. Nonsurgical or Surgical Treatment of ACL Injuries: Knee Function, Sports Participation, and Knee Reinjury. The Delaware-Oslo ACL Cohort Study. J Bone Joint Surg Am. 2014 Aug 6; 96(15): 1233–1241.

Grindem H, Granan L P, Risberg M A, Engebretsen L, Snyder-Mackler L, Eitzen I. How does a combined preoperative and postoperative rehabilitation programme influence the outcome of ACL reconstruction 2 years after surgery? A comparison between patients in theDelaware-Oslo ACL Cohort and the Norwegian National Knee Ligament Registry. Br J Sports Med 2014; 0: 1–6.
NSMC (June 2016) Lynn Snyder-Mackler – Is there a place for non-operative treatment for ACL tears presentation.

by John A. Baur, PT, DPT, OCS, CSCS, FAAOMPT

Can individuals return to sports after ACL injury without reconstruction? And, who needs surgery?

Typical pre-op rehabilitation goals include:

No pre-operative flexion contracture or quadriceps lag
– Quad contraction with superior glide of the patella
– Normal patellar mobility
Little to no effusion (swelling within the knee joint space)
Walk without a limp

What are successful outcomes?
Lynch BJSM 2015

A survey was performed on almost 2000 orthopedic surgeons, and sports/rehabilitation specialists in Europe. These specialists across-the-board only had two things that came up from virtually everybody about what successful outcomes equal success.

1) Return to sports or previous activity
Moon cohort data football in the United States found that 63% of American Football player (AFB) and 69% of high school football players (HS FB) of the players were able to return to play at the same self-described performance level. Approximately 27% felt they did not perform at the level attained before their ACL injury/tear, and 30% were unable to return to play at all.

The Moon cohort data for soccer in the United States found that 72% of soccer players returned to play.

Clare Ardern, Australian-trained physiotherapist and senior researcher in sports medicine, performed a meta-analysis in 2011 found that 63% of athletes returned to preinjury level of spots and 44% to competitive sports. This is the same results found in the Moon cohort.

Shah et al AJSM 2010 published that in NFL players underwent ACL reconstructions 61% (31/49) returned to playing in the NFL at a mean of 11 months after surgery.

Feucht et al 2014 conducted a survey of what patients think prior to undergoing ACL reconstructive surgery. The study found that 94% of primary or initial ACL reconstruction and 84% of revised ACL reconstruction expect to return to the same level of activity with no or slight restrictions. The patients’ preoperative expectations do not match the post-operative outcome data.

2) No reinjury (Does this really happen)?
– Moon cohort data found that 20% of women soccer players suffer ACL reinjury.
– Paterno et al (Hewett prevention cohort) 20% in the those 18 and younger sustained an ACL reinjury.
– Shelbourne data set showed that 17% in college age athletes and younger endured an ACL reinjury.
– Pinczewski data set revealed that ACL reinjury was 17% higher in younger athletes and in males.
– All rates were higher with allografts (tissue that is transplanted from one person to another) in younger athletes.
Contralateral, or opposite side, ACL reinjury is 12-25% higher in younger athletes and females.

Osteoarthritis was seen in 45-70% patients 15 years after ACL reconstructive surgery and higher in those who returned to strenuous sports. However, if you ask patients what they think their risk of developing osteoarthritis will be 98% will say “they have no or slight increased risk”.

After ACL revision surgery
– Patient have a worse outcome in the short-term
– Higher occurrence of osteoarthritis and higher degree of disability in the long-term.

In a study conducted by Paterno et al AJSM 2014, they followed post- ACL reconstruction patients and a control group (teammates) of the athletes who played sports that require cutting, pivoting or jumping movements for 24 months.

The study found that 29.5% of the athletes with a history of ACL reconstruction suffered a second ACL injury while only 8.5% of the control athletes suffered a first ACL injury.
The overall incidence rate of a second ACL injury was nearly 6 times greater than the control subjects in the 24-month period.

Within the ACL reconstruction group, female athletes were more than twice as likely to tear the ACL on their contralateral (opposite side) knees rather than the graft in the surgical knee.

Athletes in the ACL reconstruction group who suffered another ACL injury did so soon after they returned to play. 30.4% were injured in less than 20 athletes-exposures, and 52.2% were injured in less than 72 athletes-exposures.

In a meta-analysis conducted by Webster et al AJSM 2014 found that in patients younger than 20 years of age at the time of surgery, 29% sustained a subsequent ACL injury to either knee. The odds for sustaining an ACL graft rupture or contralateral injury increased 6- and 3-fold, respectively, for patient younger than 20 years.
Returning to cutting/pivoting sports increased the odds of graft rupture by a factor of 3.9 and contralateral rupture by a factor of 5. Also, a positive family history doubled the odds for both graft rupture and contralateral ACL injury.

In a study conducted by Wiggins et al AJSM 2016 found that secondary ACL injury rate (ipsilateral and contralateral) for patients younger than 25 years was 21%. The secondary ACL injury rate for athletes who return to a sport was also 20%. Combining these risk factors, athletes younger than 25 years who return to cutting, pivoting or jumping sport have a secondary ACL injury rate of 30%.

Are orthopedic surgeons and physical therapist appropriately counseling patients regarding ACL reconstructive surgery?

Patients see the successful ACL reconstructive surgery outcome on TV and social media.

What should orthopedic surgeons and physical therapist be counseling patients regarding ACL reconstructive surgery?

– Just because you have an ACL reconstruction, doesn’t mean that you will return to sport at all, and most likely not at the same level of performance.
– Your risk of reinjury is high in the near term or short after returning to play, reinjury is higher if you are younger, higher (ipsilateral or same side) if you are male and (contralateral or opposite side) if you are female.
– Regardless of the type of ACL reconstruction surgery, your risk of developing osteoarthritis is high in the long-term and if you need a revision of the ACL reconstruction surgery the risk of osteoarthritis is higher.

At Physical Therapy First we believe that providing true sport physical therapy requires a physical therapist who is “evidence informed and clinically astute”. Physical Therapy First works hard to stay well-informed with the best and latest true sports physical therapy research and our residency / fellowship trained physical therapist are clinically skilled and astute. We believe this makes a true difference in our patient physical outcomes and successful return to sports.

References:

Shah VM, Andrews JR, Fleisig GS, McMichael CS, Lemak LJ. Return to play after anterior cruciate ligament reconstruction in National Football League athletes. Am J Sports Med. 2010 Nov; 38 (11): 2233-9.

Kaeding CC, Pedroza AD, Reinke, EK, Laura J. Huston, LJ, MOON Consortium, and Spindler, KP. Risk Factors and Predictors of Subsequent ACL Injury in either Knee after ACL Reconstruction: Prospective Analysis of 2488 Primary ACL Reconstructions from the MOON Cohort. Am J Sports Med. 2015 Jul; 43(7): 1583–1590.

Ardern CL, Webster KE, Taylor NF, Feller JA. Return to sport following anterior cruciate ligament reconstruction surgery: a systematic review and meta-analysis of the state of play. Br J Sports Med, 2011.

Feucht MJ, Cotic M, Saier T, Minzlaff P, Plath JE, Imhoff AB, Hinterwimmer S. Patient expectations of primary and revision anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2016 Jan;24(1):201-7. doi: 10.1007/s00167-014-3364-z. Epub 2014 Oct 2.

Paterno MV, Rauh MJ, Schmitt LC, Ford KR, Hewett TE. Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport. Am J Sports Med. 2014;42(7):1567–1573.

Webster KE, Feller JA, Leigh WB, Richmond AK. Younger patients are at increased risk for graft rupture and contralateral injury after anterior cruciate ligament reconstruction. Am J Sports Med. 2014;42(3):641–647.
Wiggins Amelia, Grandhi Ravi, Schneider Daniel, Stanfield Denver, Webster Kate, Myer Gregory. Risk of secondary injury in younger athletes after anterior cruciate ligament reconstruction: A systematic review and meta-analysis Am J. Sports Med. 2016 July; 44(&): 1861-1876

Lynch A D, Logerstedt D S, Grindem H, Eitzen I, Hicks G E, Axe M J, Engebretsen L, Risberg M A, Snyder-Mackler L. Consensus criteria for defining ‘successful outcome’ after ACL injury and reconstruction: a Delaware-Oslo ACL cohort investigation. British Journal of Sports Medicine Mar 2015, 49 (5) 335-342.

NSMC (June 2016) Lynn Snyder-Mackler – Is there a place for non-operative treatment for ACL tears presentation.