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The MCL apprehension sign: A novel test for MCL instability

Published:January 18, 2023DOI:https://doi.org/10.1016/j.jcot.2023.102110

      Abstract

      Purpose

      This study describes a new clinical sign to diagnose clinically relevant medial collateral ligament (MCL) injury and evaluates its use in diagnosis and planning treatment for MCL injuries.

      Methods

      A total of 30 consecutive patients with suspected MCL injury, visiting the sports knee clinic were screened by the senior author and the knee fellow for any clinical laxity. Of these, 9 patients did not have any clinically demonstrable laxity but did have MRI evidence of MCL injury. The presence of apprehension sign was compared against the standard criteria for MCL laxity and was evaluated as a novel test to diagnose clinically significant MCL laxity.

      Results

      Of the 21 patients who were diagnosed to have MCL laxity, 18 had a positive apprehension sign at the time of presentation. Eight out of the nine patients who were negative for MCL laxity, did not have a demonstrable apprehension sign. According to the gold standard index, the apprehension sign had a sensitivity of 85.7% and a specificity of 88.8%. The positive and negative predictive values were 94.7% and 72.7% respectively. The pre-test probability of MCL laxity based on the diagnostic criteria was 70% and increased to 94.7% with a positive apprehension sign.

      Conclusions

      A positive apprehension sign is suggestive of MCL injury requiring active treatment. It also helps in deciding the length of bracing required and the need for further operative treatment. The authors recommend its use as a reliable & reproducible adjunct to standard clinic-radiological work-up for MCL injuries.

      Keywords

      List of abbreviations

      MCL
      Medial Collateral Ligament
      sMCL
      superficial Medial Collateral Ligament
      POL
      posterior oblique ligament
      ACL
      anterior cruciate ligament
      MRI
      Magnetic Resonance Imaging
      MPFL
      medial patello-femoral ligament

      1. Introduction

      1.1 Background

      The medial collateral ligament is the most commonly injured ligament in the knee.
      • Bollier M.
      • Smith P.A.
      Anterior cruciate ligament and medial collateral ligament injuries.
      • Encinas-Ullán C.A.
      • Rodríguez-Merchán E.C.
      Isolated medial collateral ligament tears: an update on management.
      • Roach C.J.
      • Haley C.A.
      • Cameron K.L.
      • et al.
      The epidemiology of medial collateral ligament sprains in young athletes.
      In spite of these injuries being common, the diagnosis, grading and management can be challenging to define.
      • Bollier M.
      • Smith P.A.
      Anterior cruciate ligament and medial collateral ligament injuries.
      • Encinas-Ullán C.A.
      • Rodríguez-Merchán E.C.
      Isolated medial collateral ligament tears: an update on management.
      • Roach C.J.
      • Haley C.A.
      • Cameron K.L.
      • et al.
      The epidemiology of medial collateral ligament sprains in young athletes.
      • Reider B.
      • Sathy M.R.
      • Talkington J.
      • et al.
      Treatment of isolated medial collateral ligament injuries in athletes with early functional rehabilitation: a five-year follow-up study.
      Early diagnosis of MCL injuries, whether isolated or as a part of a multi-ligament injury, is crucial for appropriate management.
      • Encinas-Ullán C.A.
      • Rodríguez-Merchán E.C.
      Isolated medial collateral ligament tears: an update on management.
      • Roach C.J.
      • Haley C.A.
      • Cameron K.L.
      • et al.
      The epidemiology of medial collateral ligament sprains in young athletes.
      • Reider B.
      • Sathy M.R.
      • Talkington J.
      • et al.
      Treatment of isolated medial collateral ligament injuries in athletes with early functional rehabilitation: a five-year follow-up study.
      We have described a novel clinical sign, which not only helps in diagnosing an MCL injury but also guides further management. It helps in deciding the duration of bracing as the resolution of this sign after bracing can be considered as an indicator of completion of conservative treatment. However, if the sign is still positive on clinical examination after bracing the knee for the initial period, it indicates that further bracing is required. The sign also helps in identifying under-treated or maltreated cases with chronic MCL laxity.

      1.2 The MCL apprehension sign

      The MCL apprehension sign is a clinical sign which is performed with the patient supine. With the injured knee flexed to about 20–30°, a valgus stress is applied to the knee. Medial thigh is observed for a reflex muscle contraction of semimembranosus muscle (Fig. 1, Fig. 2). We have noticed a stretch reflex involving the semimembranosus tendon which is consistently present in cases of MCL injury with laxity (Video 1). This is a sign of symptomatic MCL laxity. This sign is observed both in the acute and chronic neglected/under-treated MCL instability and disappears when the instability resolves following successful treatment. Although it does not grade the MCL injury, however, does differentiate between MCL injuries requiring treatment from the ones which do not.
      Fig. 1
      Fig. 1Clinical photograph showing patient's left knee held in a position of about 30° of flexion before applying the valgus stress.
      Fig. 2
      Fig. 2Clinical photograph demonstrating a positive MCL apprehension sign which can be observed as a reflex contraction of semimembranosus on application of valgus stress.
      The following is the supplementary data related to this article.
      The time when the patient presents to a sports knee clinic or a fracture clinic, he/she is already a few days following the injury
      • Phisitkul P.
      • James S.L.
      • Wolf B.R.
      • et al.
      MCL injuries of the knee: current concepts review.
      and the sign can be observed consistently. However, care must be taken to differentiate it with contraction of the whole quadriceps and adductor sleeve, which can be present because of a response to pain.
      • Phisitkul P.
      • James S.L.
      • Wolf B.R.
      • et al.
      MCL injuries of the knee: current concepts review.

      1.3 The proposed anatomical & bio-mechanical basis of the test

      We do not have experimental data to substantiate these findings; however, we can hypothesize the patho-anotomy of this sign. The medial soft tissue sleeve around the knee comprises of static and dynamic stabilizers. The superficial MCL (sMCL) is the most important static stabilizer to valgus stress. The posterior fibers of the sMCL coalesce with the fibers from the deeper fibers and form the posterior oblique ligament (POL) which remains contiguous with the posteromedial capsule.
      • Phisitkul P.
      • James S.L.
      • Wolf B.R.
      • et al.
      MCL injuries of the knee: current concepts review.
      ,
      • Warren L.F.
      • Marshall J.L.
      The supporting structures and layers on the medial side of the knee: an anatomical analysis.
      The semimembranosus complex is one of the most important dynamic stabilizers of the knee medially and is present deep to sMCL. The semimembranosus tendon has a primary insertion on the proximal tibia just below the joint line posteromedialy with extensions to posterior oblique ligament, oblique popliteal ligament and the popliteal fascia. In a normal knee, the semimembranosus complex provides little in the way of static stability in extension or 20–30° of flexion, as the majority of it is provided by sMCL which is present superficial to it. It is majorly recruited during flexion activities to prevent meniscal impingement and acts through its insertion on posterior oblique ligament.
      • Encinas-Ullán C.A.
      • Rodríguez-Merchán E.C.
      Isolated medial collateral ligament tears: an update on management.
      ,
      • Phisitkul P.
      • James S.L.
      • Wolf B.R.
      • et al.
      MCL injuries of the knee: current concepts review.
      • Warren L.F.
      • Marshall J.L.
      The supporting structures and layers on the medial side of the knee: an anatomical analysis.
      • Hughston J.C.
      • Eilers A.F.
      The role of the posterior oblique ligament in repairs of acute medial (collateral) ligament tears of the knee.
      However, in an injured knee with an incompetent sMCL, when valgus stress is applied, the semimembranosus tendon complex is exposed to the stretching force much earlier than normal, which in turn, gives rise to a stretch reflex which leads to the contraction of the semimembranosus muscle in the posteromedial thigh (Video 1 & Fig. 1, Fig. 2). This is usually very evident and is observed as a positive MCL apprehension sign.
      This stretch reflex giving rise the apprehension sign, was first clinically observed by the senior author and it was decided to validate its usefulness clinically.

      2. Materials and methods

      To determine the clinical implication and use of the MCL apprehension sign a prospective observational study was carried out in the sports injury unit at a tertiary referral hospital. The study included 30 consecutive patients with a suspected diagnosis of isolated MCL injury or a multi-ligament injury involving MCL injury. The MCL injury was suspected based on the injury mechanism, history and clinical findings of tenderness and instability. The MCL injury was graded using Fetto & Marshall's classification.
      • Fetto J.F.
      • Marshall J.L.
      Medial collateral ligament injuries of the knee: a rationale for treatment.
      Grade I included patients with tenderness along the MCL with no clinically demonstrable laxity on valgus stress either in 30° or in full extension. Grade II had demonstrable laxity on valgus stress but with an end point, and Grade III injuries had demonstrable laxity in both 30° of flexion and in full extension with no end point.
      • Fetto J.F.
      • Marshall J.L.
      Medial collateral ligament injuries of the knee: a rationale for treatment.
      Out of this cohort, to be classified to have a diagnosis of MCL laxity the patient was required to have both the following findings.
      • 1.
        A positive clinical finding of MCL laxity on examination conducted by the senior author i.e. increased joint opening on valgus stress in 30° of flexion only or in both 0 and 30° of flexion, as compared to the normal uninjured knee (Fetto & Marshal Grade II & III).
      • 2.
        Evidence of MCL injury on Magnetic Resonance Imaging (MRI) scan, confirmed by both, the senior author and the reporting radiologist.
      When these two findings were present, a diagnosis of MCL laxity was established and the patients were treated as disease positives for statistical calculations. All the 30 patients were simultaneously assessed for the presence of apprehension sign by the senior author first and then by the knee fellow, in a blinded fashion (without knowing the MRI findings or findings of clinical examination by senior author). Only the injured knee was examined by the knee fellow to ascertain and document the presence or absence of apprehension sign to provide information on the inter-rater reliability. The examination by the knee fellow was limited to the injured knee and the diagnosis of MCL laxity was blinded from him to give an unbiased picture of the reliability.
      For statistical calculations, the clinico-radiological diagnosis of MCL laxity was treated as the gold standard and the new clinical test, MCL apprehension was compared against it. The patients who satisfied the above-mentioned criteria were treated as disease positive as there is no other objective or intra-operative evidence available to ascertain MCL injury. The patients who did not satisfy the criteria for MCL laxity were treated as disease negative. A 2∗2 contingency table (Table 1) was formulated, and the sensitivity, specificity, predictive values and likelihood ratios were calculated to determine the diagnostic accuracy and utility of the apprehension sign. Approval from the Institutional Ethical & Review Board was obtained. Informed consent was obtained from the patients regarding use of their data.
      Table 12 × 2 contingency table for calculating the diagnostic parameters of MCL apprehension test for MCL laxity.
      MCL Apprehension test
      PositiveNegativeTotal
      MCL Laxity (based on the mentioned criteria)Positive18321
      Negative189
      Total191130

      3. Results

      A total of 30 consecutive patients with suspected MCL injury, visiting the sports knee clinic were screened by the senior author and the knee fellow. Of these, 9 patients did not have any clinically demonstrable laxity but did have MRI evidence of MCL injury and hence did not satisfy our clinical criteria of MCL laxity. All of these 9 patients had tenderness along the MCL and had had a probable partial injury to MCL and were classified as grade I injuries.
      Remaining twenty-one patients satisfied the clinico-radiological definition of MCL laxity and hence were included in the study. Of these 30 patients, 24 were males and 6 females. The mean age of the cohort was 27.2 years (range 19–42). Fourteen patients were professional rugby players and had a contact injury while playing competitive rugby. Four patients had the injury while playing professional football. In six patients, injury was purely non-contact in nature and was sustained while skiing. One of the patients had this injury after a motorbike accident and the other two injuries were sustained while playing recreational sports. The remaining three patients had the injury following a fall which involved a twisting injury to the knee (Table 2).
      Table 2Demographic data.
      Characteristics
      Mean Age27.2±3.4 years (Range - 19–42)
      Side of Involvement16 right; 14 left
      Gender24 Males; 6 females
      Presentation28 Acute; 2 Chronic
      Time since injury (for acute presentations)8.7±1.2 days (Range - 2–42 days)
      Cause
      Professional Rugby14
      Professional Football4
      Skiing6
      Recreational Sports2
      Twisting injury/Fall3
      Motor vehicular accident1
      Twenty-eight patients out of 30 confirmed a valgus nature of injury in the history. It was a right sided injury for 16 patients and a left sided injury for rest 14 patients. Twenty eight of these patients had an acute presentation and were seen in the clinic within 6 weeks of having the injury with a mean time to presentation of 8.7 days (range 2–42 days). Two patients had a chronic injury and presented 1 year and 8 years following the injury.
      Out of the 30 patients, 11 had associated anterior cruciate ligament (ACL) deficiency which was evident both clinically and radiologically. Seven out of these eleven patients satisfied the criteria for MCL laxity and four did not.
      The MCL injury was located at the femoral insertion in 16 patients, mid substance in 11 patients and tibial sided in 3 patients on the MRI scan. One patient had a complete tibial avulsion of MCL and had Stener-type lesion evident on MRI scan.
      Of the 21 patients who were diagnosed to have MCL laxity based on the aforementioned criteria, 18 had a positive apprehension sign at the time of presentation, when assessed independently by two separate examiners (Table 3). These patients were graded to have grade II laxity and did have a definite end point on valgus stress. For three patients neither of the examiners could demonstrate a positive apprehension sign. Two of these 3 patients had a 3+ laxity and did not have a demonstrable end point to valgus stress. Nineteen of these 21 patients had an acute presentation and all except one of these acute injuries were treated initially with early active mobilization in a hinged knee brace, with 0–90° of flexion and allowance of weight bearing as tolerated, for 6 weeks following time of injury, irrespective of the associated ACL injury. One patient presented acutely with a Stener-type injury on the tibial side of MCL, had a grade 3+ laxity and underwent an early reattachment of the MCL. Two patients who presented with chronic laxity had associated ACL injuries as well. They underwent a combined ACL and MCL reconstruction later electively.
      Table 3Classification of patients based on Fetto & Marshall's grading of MCL Injury and co-relation with the apprehension sign.
      Fetto & Marshall gradingNo. of patients in each gradePositive apprehension sign
      Grade I91
      Grade II1918
      Grade III20
      Eight out of the nine patients who were negative for MCL laxity i.e. Grade I MCL injury, did not have a demonstrable apprehension sign by either of the examiners (Table 3). One patient had a demonstrable apprehension sign by one of the examiners (senior author) but not by the other. This patient was counted as apprehension positive without having any increased MCL laxity. Four of these nine patients had an associated ACL injury and three had a medial patello-femoral ligament (MPFL) injury. Early treatment for the MCL injury in these 9 patients was dependent on their mechanical alignment and were mobilized without a brace unless they had significant valgus alignment.
      According to the gold standard index,
      • Parikh R.
      • Mathai A.
      • Parikh S.
      • et al.
      Understanding and using sensitivity, specificity and predictive values.
      the apprehension sign had a sensitivity of 85.7% and a specificity of 88.8%. Likelihood ratios and the predictive values were computed based on these figures. The positive and negative predictive values were 94.7% and 72.7% respectively, indicating that the apprehension sign can be used as a precise and accurate tool in a similar setting like ours with a similar prevalence of such injuries. The positive and negative likelihood ratios were 7.7 and 0.16 respectively (Table 4).
      Table 4Diagnostic parameters for MCL Apprehension sign.
      Sensitivity85.7%
      Specificity88.8%
      Positive predictive value94.7%
      Negative predictive value72.7%
      Positive likelihood ratio7.7
      Negative likelihood ratio0.16
      Pre-test probability70%
      Post-test probability94.7%
      To calculate the diagnostic accuracy of the apprehension sign the likelihood ratios and the pre-test probability of MCL laxity (21 out of 30 i.e. 70%) were plotted on the Fagan's nomogram.
      • Deeks J.J.
      • Altman D.G.
      Diagnostic tests 4: likelihood ratios.
      The pre-test probability of MCL laxity based on the diagnostic criteria was 70% and increased to 94.7% with a positive apprehension sign. The post-test probability from a negative apprehension sign reduced the likelihood of having MCL laxity to 27%. This was a significant change in probability and hence the sign was considered a useful and accurate adjunct. The inter-rater reliability co-efficient kappa was 0.96 indicating high level of agreement which further substantiates the use of this as an adjunct to clinical evaluation.
      This cohort of 30 patients was followed at 6 weeks following the start of treatment, be it non-operative or operative. Patients who received a non-operative intervention for clinical MCL laxity following an acute injury (18 patients) were reassessed clinically using the same criteria at 6 weeks. If at 6 weeks follow up they still had persistent laxity the bracing was continued for another 4 weeks. It was noted that the apprehension sign disappeared as soon as the laxity ceased to exist. Patients who received operative intervention for chronic laxity did not have an apprehension sign on examination at 6 weeks following stabilization.

      4. Discussion

      MCL Injury, with symptomatic laxity can be difficult to diagnose.
      • Bollier M.
      • Smith P.A.
      Anterior cruciate ligament and medial collateral ligament injuries.
      ,
      • Encinas-Ullán C.A.
      • Rodríguez-Merchán E.C.
      Isolated medial collateral ligament tears: an update on management.
      ,
      • Reider B.
      • Sathy M.R.
      • Talkington J.
      • et al.
      Treatment of isolated medial collateral ligament injuries in athletes with early functional rehabilitation: a five-year follow-up study.
      The grading or classification can be difficult and can only be mastered with experience. The classification systems available in literature differ from each other in principles and are based on the measurement of joint opening which is very subjective.
      • Phisitkul P.
      • James S.L.
      • Wolf B.R.
      • et al.
      MCL injuries of the knee: current concepts review.
      ,
      • Fetto J.F.
      • Marshall J.L.
      Medial collateral ligament injuries of the knee: a rationale for treatment.
      ,
      • Perryman J.R.
      • Hershman E.B.
      The acute management of soft tissue injuries of the knee.
      ,
      • Sims W.F.
      • Jacobson K.E.
      The posteromedial corner of the knee: medial-sided injury patterns revisited.
      This dilemma in grading these injuries poses significant difficulty, not only in decision making regarding the management but also in determining the adequacy of treatment. This is accentuated when the knee is examined by two different clinicians in successive follow up clinic appointments, as the quantification of joint opening on valgus stress may not have a good inter-observer agreement.
      • Phisitkul P.
      • James S.L.
      • Wolf B.R.
      • et al.
      MCL injuries of the knee: current concepts review.
      ,
      • Wood L.
      • Peat G.
      • Wilkie R.
      • et al.
      A study of the noninstrumented physical examination of the knee found high observer variability.
      This study describes a clinical sign to mitigate this problem.

      4.1 Strengths

      The apprehension sign is easily demonstrable as it is a visible response and is comparatively more objective than grading of joint opening. It has a strong sensitivity and specificity when compared to the gold standard diagnostic aids. Its effect on the pre-test probability indicates that it is a worthwhile tool. The high inter-rater agreement observed signifies that the test is independent of the examining clinician's experience and is easily reproducible.
      The fact that it helps in deciding the prognosis and in deciding the further need of treatment increases its usefulness.
      Another strength of the study is the avoidance of selection bias as all the patients being suspected of MCL injury of any grade were included based on history and initial clinical examination. The cohort definitely consists of an appropriate number of acute injuries to conclusively prove the clinical usefulness of the MCL apprehension sign, however, further studies may be required to confirm the same for chronic MCL injuries. The study did not have sufficient number of chronic MCL laxity patients to draw any conclusions on either the presence or the usefulness of the apprehension sign. The study supports the use of this sign specifically for Grade II & III MCL injuries. The presence of other associated ligamentous injury, which is most commonly ACL injury, did not affect the results of the test, as seen on subgroup analysis.

      4.2 Shortcomings

      There are few shortcomings to this study which we intend to minimize or eradicate in later studies. An inevitable assessor bias may have been introduced as the apprehension sign can only be observed when performing the valgus stress testing and blinding of the clinical examiner is practically not possible in this scenario. Involvement of two independent observers minimizes it to a certain extent but does not eliminate it.
      Secondly, the gold standard used in this study is assessor dependent and is subjective but there is no reliable objective method available to confirm a MCL injury unlike an ACL or a meniscus injury where an into-operative assessment of injury is treated as the gold standard.
      Also, the sample size in this study may be inadequate statistically but was deemed to be clinically relevant due to difficulties in recruiting large number of patients.
      Thirdly, the number of cases having Grade III injuries was small, this being a rare injury. With such small numbers in this subgroup, definite conclusions can not be drawn regarding the apprehension test in this subgroup. If the valgus stress (working as the stretch on the tendons providing the afferent signals for the reflex) is excessive, then the desired reflex contraction may not be demonstrable. The temptation to apply excessive valgus stress has to be resisted to prevent this.
      Caution is to be exercised while assessing this clinical sign as it can be mimicked or confused by generalized quadriceps and/or adductor contraction which can be present during the initial phase after an injury.
      • Phisitkul P.
      • James S.L.
      • Wolf B.R.
      • et al.
      MCL injuries of the knee: current concepts review.
      ,
      • Hughston J.C.
      • Andrews J.R.
      • Cross M.J.
      • et al.
      Classification of knee ligament instabilities. Part I. The medial compartment and cruciate ligaments.
      This usually settles in 48–72 h and is a global contraction of the whole anteromedial muscular sleeve rather than semimembranosus alone. In cases of clinical MCL laxity, the apprehension sign is observed on the medial aspect of thigh as demonstrated in the figures (Fig. 1, Fig. 2), whereas if it's a response to pain the whole quadriceps bulk can be seen contracting, which is visualized more anteriorly on the thigh.

      5. Conclusion

      To conclude, the authors strongly recommend the use of this clinical sign which is safe, easily demonstrable, reproducible and accurate, as an adjunct to standard clinical examination and radiological evidence. A positive MCL apprehension sign indicates an MCL injury requiring active treatment.

      6. Summary

      • MCL apprehension sign is a new test to diagnose cases with MCL laxity.
      • A positive apprehension sign is suggestive of MCL injury requiring active treatment.
      • It also helps in deciding the length of bracing required and the need for further operative treatment.
      • It is highly sensitive and specific and is reliable and reproducible to use.

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