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Classification of functional recovery of anterior cruciate ligament copers, non-copers, and adapters

Button, K., van Deursen, R. and Price, P., 2006. Classification of functional recovery of anterior cruciate ligament copers, non-copers, and adapters. British Journal of sports medicine, 40(10), pp.853-859.

In today’s letter

• Understanding copers & non-copers function with ACL deficient knee

• Rapid Results =

1. Copers, adapters, and non-copers have different recovery patterns that can be identified clinically.

2. Gait recovery is more useful than hopping distance for assessing ACLD patients up to five months after injury.

3. There is a very low rate of functional coping among ACLD patients who had high sporting demands before their injury.

• 3 Reads to check out to further you knowledge about copers & non-copers

• Meme of the week: Oh the special tests 😄 

Aim of the study

• The goal is to find out if there are differences in how ACL deficient copers, adapters, and non-copers recover.

• This study aims to identify key clinical outcomes that can help distinguish between these three functional groups

Did you know?

• Surgery is often considered the best treatment for patients with an anterior cruciate ligament (ACL) deficiency who want to return to high-intensity activities or experience knee instability.

• Some patients choose non-surgical (conservative) treatment, depending on their lifestyle and activity level.

• Patients with ACL deficiency can be grouped into "copers," "non-copers," and "adapters" based on their ability to return to activities, which leads to different recovery outcomes.

• Not grouping patients correctly can result in inaccurate evaluations of their performance, affecting their treatment

• Screening tools exist to identify potential "copers" among ACL deficiency patients, helping guide treatment decisions.

• These tools, while useful, do not provide information into how recovery progresses over time for each group and are mainly designed for athletes.

• The tools also don’t provide enough information to make early decisions about long-term treatment, especially for non-athletes.

Copers, adapters & non-copers

Coper = A coper is defined as a patient who has returned to their pre-injury level of work and sport with no limitations in their performance

Adapter = An adapter is someone who has reduced their work or sport level or changed activities to prevent their knee fully giving way

Non-coper = Non-copers are patients who fail to return to their pre-injury activities and are experiencing episodes of full giving way with work, activities of daily living, or low demand, non-pivoting sports

Timed 6 meter hop: LINK

Knee outcome survey: LINK

Global rating score: Patients rate their knee function from 0 to 100, where 0 means no function and 100 means full function like before the injury

 Methods

Subjects

• From May 2001 to November 2003, 281 patients with an acute ACL rupture were seen at the Acute Knee Screening Service at the University Hospital of Wales, with diagnoses confirmed by MRI.

Inclusion & exclusion

Patients were excluded from the study if they:

1. Had other neurological or musculoskeletal conditions

2. Required urgent knee surgery

3. Had combined ACL and PCL injuries

4. Lived outside the hospital’s catchment area for physiotherapy.

• A total of 42 patients were eligible for the final analysis, while 21 were excluded due to incomplete movement analyses or being unreachable for follow-up 12–36 months after the injury.

• A control group of 61 individuals without knee injuries, from the same area, was recruited to match the patients with ACL injuries for comparison.

• All patients followed a rehabilitation program focused on achieving full range of motion, strengthening muscles, and improving neuromuscular control.

Movement analysis

• Distance hopping was recorded if subjects had minimal resolving effusion, full range of knee motion, and no episodes of full giving way

• For maximal hopping distance, subjects were instructed to start on the leg being tested, hop as far as they could, and land on the same leg, maintaining their balance until instructed to move away

Follow up

• At 12–36 months after injury, subjects were followed up with a telephone questionnaire.

• They were asked about episodes of knee instability and current work and sport level.

• This was compared with their pre-injury activity level, and they were then classified as functional copers, adapters, or non- copers

Results

Subjects

• The ACL deficient patients in the study were matched with control subjects based on age, height, weight, and activity levels.

Of the 42 patients followed for 12 months:

1. 17% were classified as copers

2. 45% as adapters

3. 38% as non-copers

4. Only 5% of those who participated in high-demand activities before their injury returned to them.

Gait

• Figures 1–3 show the average recovery patterns for various gait variables across different ACL deficient subgroups

• Table 4 highlights the number of days it took for each subgroup and the average ACLD patients to reach "normal" limits based on control subjects.

• Initially, all ACL deficient subgroups showed gait variables below the normal range compared to control subjects right after the injury.

• Over time, the recovery patterns of the subgroups became more distinct, showing different rates of improvement relative to the control group average.

• If all ACL deficient patients are considered as one group, it may falsely appear that, on average, they recover to the same level as the control subjects.

• For non-copers, walking speed (velocity) improved but only reached the lower end of the normal range and then plateaued.

• Step length for non-copers returned to near the control mean but then worsened slightly and stabilised within the lower "normal" range.

• All subgroups recovered their walking cadence (steps per minute) to within 1 standard deviation of the control mean, with copers recovering quickly.

• Adapters generally recovered and stabilised close to the control mean, copers slightly above it, and non-copers at the lower end of the normal range.

• Copers showed the fastest recovery in all gait variables and reached normal limits within 40 days of injury.

Hopping distance

• Pain, swelling, and instability prevented 10 non-copers with ACL injuries from participating in the hopping test.

• As a result, the analysis is based on a smaller sample, which may introduce bias into the results.

• On average, the entire group of ACL deficient patients seemed to recover to match the performance of the control group.

• When split into subgroups (copers, adapters, and non-copers), non-copers initially hopped the shortest distance but surpassed the other groups by day 150.

• Copers were within the lower limit of the control group's performance by day 30, but they did not reach the control group's average hopping distance

Discussion

Overall

• Between 12 and 36 months after injury, ACL deficient patients were categorised as functional copers, non-copers, or adapters based on whether they could return to their pre-injury activities without knee instability (giving way).

• Most patients fell into the adapter or non-coper groups, which is consistent with existing research.

• This study found fewer copers compared to other studies, especially among those who had high sporting demands.

• Recovery was tracked over time for various biomechanical variables like gait and hopping distance to identify distinct patterns of recovery for each group.

• Functional copers and adapters mostly recovered within normal limits, but non-copers remained borderline in their recovery.

Gait

• After the injury, all ACL deficient patients, regardless of subgroup, initially compensated by walking with a slower speed (gait velocity) and taking shorter steps (step length).

• Non-copers struggled to return to the normal limits for most gait variables, compared to control subjects.

• In contrast, all gait variables for copers returned to normal within 40 days after the injury, making them distinguishable from non-copers by that time.

• Functional adapters had a recovery similar to copers, but it was difficult to pinpoint when they became distinguishable from copers based on gait patterns.

• Non-copers frequently experienced episodes of knee instability ("giving way") during work, daily activities, or low-demand sports, leading to compensation strategies for daily tasks.

• The only other study to track gait recovery over time found that it took 2.8 to 4 weeks for patients to regain independent, normal walking without limping (non-antalgic gait

Hopping Distance

• The 2nd functional activity analysed in the study was hopping distance, a more challenging test for ACL deficient patients due to the high forces involved.

• All ACL deficient subgroups were expected to use compensation strategies when hopping

• Surprisingly, non-copers in this study demonstrated high hopping distances, though this may be biased since some non-copers couldn’t hop due to knee instability, skewing the results.

• One possible explanation for copers hopping a shorter distance is that many of them didn’t participate in high-demand sports like jumping and pivoting before the injury, so they lacked the ability to excel at hopping.

• Another explanation is that copers may have a functionally stable knee by knowing their limits, which might result in them hopping shorter distances to avoid instability.

• While hopping is often considered a key functional test after ACL injury, this study suggests that gait may provide more useful information for clinical decision-making in the first five months post-injury.

Sports Participation Before Injury

• Non-copers and adapters participated in sports that required a lot of jumping and pivoting before their injury, while copers did not.

• Previous research supports this finding, showing that patients who spent more time in jumping and cutting sports before injury tend to have worse outcomes.

• Overall, ACL deficient patients who received conservative (non-surgical) management had poor outcomes, despite following rehabilitation guidelines.

• The results suggest that if a patient’s gait has not recovered within 40 days after injury, or if they have high sporting demands, they are unlikely to become a functional coper.

3 resources to check out

1. Good summary of what is known about copers & non-copers - LINK

2. Rehab protacol for non-operative ACL knee - LINK

3. Fun little video discussing copers & non-copers (VIDEO) - LINK

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