Posterior Capsulotomy of the Knee: Treatment of Minimal Knee Extension Deficit.

The loss of knee extension, even if minimal, is disabling and considerably affects the individual's quality of life. This loss of extension can be a consequence of prior surgery, including a previous anterior cruciate ligament reconstruction. Although this loss of extension may be treated through an isolated arthroscopic procedure, a more severe case may warrant an invasive approach. In these cases, a posterior capsulotomy of the knee may be done if all conservative measures have been exhausted. This procedure has been proven to be safe and effective in the re-establishment of full extension in the setting of a minor flexion contracture of the knee. The purpose of this Technical Note was to describe our preferred technique when performing an open posterior capsulotomy of the knee for the treatment of minimal extension deficit.

The lack of knee extension is challenging to treat because of the variety of complaints and overall decrease in the quality of life associated with this pathology. The etiology resulting in the lack of knee extension may be acute, such as involvement in a motor vehicle accident, or chronic, such as repetitive microtrauma due to participation in sport activities. Moreover, it may be a consequence of a prior surgical procedure.1, 2 Regardless the cause, the consequences and overall injury pattern associated with lack of knee extension are generally similar: quadriceps weakness unresponsive to exercises, anterior knee pain, and a progressive inability to practice physical activities. As a result of the inability to appropriately extend the knee, many patients begin to feel anterior knee pain even for activities of daily living, including walking on a flat surface or climbing stairs. In the setting of a major traumatic event or prior surgical treatment, development of arthrofibrosis may occur and result in limitation in range of motion with initial treatment centered on arthroscopic release of the anterior adhesions of the knee.5, 6 However, this procedure may not fully restore the range of motion; therefore, a more invasive procedure capable of a full release and correction of the deficit may be necessary. For such cases, an open posterior capsulotomy is a reasonable treatment option. An open posterior capsulotomy may also be undertaken in cases of knee extension deficit secondary to multiple lesser trauma events as a result of regular participation in sports. Nevertheless, this procedure is not recommended for those with tibiofemoral osteoarthrosis or for whom other, less invasive treatment options have not been tried. Indications and contraindications are summarized in Table 1.

Table 1

Indications and Contraindications of the Technique

Indications	Contraindications
Contracture of the knee of 10° or moreFailure of other treatment options less invasive	Tibiofemoral osteoarthrosisGastrocnemius muscular shortening

However, this procedure is not free of potential complications given the close proximity of several neurovascular structures. Furthermore, there remains a lack of long-term follow-up studies reporting on outcomes following this procedure. Moreover, genu recurvatum resulting from an excessive posterior release to correct the extension deficit is also, at least theoretically, a potential adverse effect of a posterior capsulotomy. The purpose of this Technical Note is to describe our preferred technique when performing an open posterior capsulotomy of the knee for the treatment of minimal extension deficit.

Surgical Technique

Patient Positioning

The patient is placed supine on the surgical table (Video 1). Following induction of general anesthesia, a thigh tourniquet is placed on the proximal aspect of the operative limb. Both knees are then prepared and draped in a sterile fashion. Before starting the procedure, the following examination under anesthesia is performed to assess the degree of extension deficit: first, the knees are placed at the same level and then the distance between the heel and the surgical table is noted for each limb. The affected knee with the extension deficit will demonstrate a shorter distance between the heel and surgical table than the contralateral limb. To confirm these findings, the heels are placed at the same level. If the knee with the extension deficit is at a greater height than the contralateral, nonsymptomatic knee, then this provides further evidence of flexion contracture of the knee (Fig 1). We believe that this physical examination is reliable and reproducible and, ultimately, allows for a thorough comparison between the affected and contralateral limb. Moreover, this technique is easily performed directly prior to surgery and provides confirmation of the diagnosis before proceeding with the surgical treatment. However, if an extension deficit is suspected in both knees, then this physical examination is not applicable. Following the physical examination, the surgical limb is exsanguinated. Afterward, the tourniquet is inflated to 250 to 350 mmHg.

Fig 1

To evaluate the loss of knee extension, we perform a physical examination following general anesthesia. As the patient lies supine on the surgical table, the knees are placed at the same level and then the distance between the heel and surgical table is noted for each limb. The affected knee with the extension deficit will demonstrate a shorter distance between the heel and surgical table than the contralateral limb. In this figure, the extension deficit is seen in the left knee.

Skin Incision and Approach

The medial femoral epicondyle is identified, and then a 4-cm incision is performed from the posterior edge of the medial epicondyle and extended posteriorly to the medial femoral condyle. The subcutaneous tissue is then carefully dissected, taking care to avoid the infrapatellar branch of saphenous nerve and vein. Following the initial incision, an oblique incision is performed across the medial retinaculum (Fig 2). Following this, the thin and translucent layer of the posteromedial synovial recess is visualized.

Fig 2

Following the initial incision in the affected left knee, the medial retinaculum and vastus medialis (black dots). An incision is performed obliquely from proximal to distal (white dots), and then the posteromedial capsule of the knee can be accessed and evaluated.

Posterior Capsulotomy of the Knee

A 2-cm incision is then performed on the posteromedial capsule with an electrocautery to arrive at a full exposure of the posterior compartment. At this point, we suggest careful palpation to identify key posterior knee structures and landmarks including the posterior cruciate ligament, posterior borders of the femoral condyle, and posterior capsule. Careful palpation is absolutely imperative given the small incision that does not allow for full visualization of all structures and landmarks. The release of the capsule is then progressively performed from medial to lateral through use of a combination of electrocautery and curved osteotomes, which are progressively moved from distal to proximal to arrive at a full release of the femoral attachment of the capsule (Fig 3). In our procedure, the tibial capsule attachment, unlike the femoral attachment, is preserved. The complete release of the posterior capsule must be achieved with care taken to avoid potential damage to the neighboring neurovascular structures. In some cases, a release of the medial gastrocnemius head may also be done in addition to the release of the capsule.

Fig 3

Once the capsule is accessed in the left knee, a rougine is used to detach the posterior capsule insertion on the medial and lateral femoral condyles. The release must be completed and performed from medial to lateral. Of note, care must be taken to avoid damage to the meniscus or neurovascular bundle.

Checking and Confirming the Release

The posterior compartment of the knee is then thoroughly palpated once more to verify if any residual capsular attachments remain. At this point, any remaining capsular attachments are released to arrive at a full and thorough capsulotomy. Afterward, scar tissue formation and adhesions are released through use of a monopolar electrocautery device (Fig 4). As the final step of verification, the posterior femoral condyle and medial meniscus are visualized and palpated to confirm a thorough release (Fig 5). Then, the correction of the extension deficit is examined through physical examination as previously described. First, the knees are placed at the same level. If the distance between the heel and surgical table is not equal for the limbs, then this provides evidence of an incomplete release. For further confirmation if an incomplete release is suspected, the heels are placed at the same level. Once the heels are placed at the same level, then the knees, both affected and contralateral, should demonstrate unequal distances to the surgical table. Ultimately, if unequal distances are noted in each of these portions of the physical examination, then this demonstrates evidence of flexion contracture that requires further release. If further release is needed, then careful manipulation may be performed by applying an anterior to posterior force on the affected knee to fully resolve the flexion contracture (Fig 6). In some cases, a posterolateral incision may be needed to release the lateral aspect of the posterior capsule when the posteromedial approach is insufficient. Following the manipulation and prior to closure, the extension deficit is inspected once more. Once a full restoration of knee extension is confirmed, the wound is closed (Fig 7).

Fig 4

A monopolar electrocautery device is used to remove scar tissue and any remaining capsular thickening following the use of the rougine on the left knee. Care must be taken to not harm the neurovascular bundle or posterior cruciate ligament attached on the tibial plateau.

Fig 5

Once the capsulotomy is fully performed, the medial femoral condyle and posterior horn of the medial meniscus of the left knee can be easily visualized. During this step, palpation of the lateral structures is absolutely necessary to evaluate the capsular release. In some cases, a lateral incision must be done to achieve a complete resection.

Fig 6

If any extension deficit remains in the left knee, a careful manipulation may be performed by applying an anterior to posterior force on the knee to fully resolve the flexion contracture. The assistant slightly raises the affected limb from the table (yellow arrow), and then the surgeon applies a series of 5 to 10 pushes on the knee from anterior to posterior, thereby forcing further extension until knee extension is equal for each limb.

Fig 7

The final result of our technique is checked using the same physical examination as done prior to surgery. At this time, both heels must be at the same distance from the surgical table when each knee is leveled. This confirms the resolved deficit in knee extension of the left knee.

Wound Closure

The wound is copiously irrigated with saline solution. Following this, a combination of ropivacaine 7.5 mg/mL (20 mL) and epinephrine (2 mL) are injected in the subcutaneous layer over the medial incision to maximize hemostasis. Afterward, the tourniquet is released and a coagulator is used for hemostasis. The capsule must remain open as the retinaculum and subcutaneous layer are closed with no. 1.0 Vicryl suture (Ethicon, Somerville, NJ) and no. 2.0 Vicryl suture (Ethicon), respectively. The skin layer is then closed through use of no. 4.0 Mononylon suture (Ethicon). The advantages and disadvantages and pearls and pitfalls associated with the described procedure are listed in Tables 2 and 3, respectively.

Table 2

Advantages and Limitations of the Technique

Advantages	Limitations
Direct visualization of posterior structures of the kneeDirect palpation of scars and capsule thickeningComplete release of the posterior capsuleSmall skin incision	Risk of damaging the neurovascular bundle and PCLHematoma in the posteromedial compartment of the kneeMinimal risk of progressive posterior knee laxity and genu recurvatum

PCL, posterior cruciate ligament.

Table 3

Pearls and Pitfalls of the Technique

Pearls

Pitfalls

Careful tissue dissection is paramount to avoid damage to the neurovascular bundleComplete the detachment of the femoral capsule from medial to lateralSearch for any scar tissue formation or residual capsular attachments by direct palpationLeave the tibial insertion of the knee capsule intactLeave the capsule open while performing wound closureCareful manipulation of the limb is necessary to release any residual capsular attachment points

Inaccurate identification of structures and landmarksDamage of the neurovascular bundle, PCL, and posterior horn of the meniscus may occur during capsular release, if performed inadequatelyIncomplete release of the posterior capsule may result in surgical failure

Postoperative Rehabilitation

Following the procedure, the affected limb is kept in a brace in extension for 7 days. Nonsteroidal anti-inflammatory drugs are prescribed and taken to control the physiological response to surgical trauma. Physical therapy is then initiated once the brace is removed at 7 days following surgery. The ultimate goal of the rehabilitation program is to maintain the knee extension that was achieved as a result of the procedure. Moreover, most patients with chronic loss of knee extension also demonstrate atrophy of the quadriceps muscle, which is addressed through physical therapy.

Discussion

The inability to fully extend the knee joint as a result of a traumatic event or prior surgery may be tolerable to sedentary and minimally active patients. However, this becomes a limiting issue for those involved in sports and leading active lifestyles in a very short period of time. Traditional surgery performed to treat patellofemoral disorders has been proven to be ineffective if the issue is due to excessive pressure over the cartilage imposed by the lack of full extension. Although the cartilage of the patellofemoral joint is one of the thickest and most durable in the body, prolonged flexion contracture of the knee results in a force overload on the joint with an accompanying increase in subchondral intraosseous pressure due to the increase in force seen with an increasing flexion angle of the knee. Therefore, a lateral retinaculum release, Maquet Procedure or Fulkerson osteotomy may be effective in the treatment of malaligment of the knee. However, these procedures cannot resolve flexion contracture of the knee, which compromises extension of the knee and results in force overload on the patellofemoral joint. Therefore, a posterior capsulotomy may be performed to resolve the deficit in knee extension. Because of the potential risks associated with this procedure including progression to genu recurvatum, this procedure is not performed on a widespread basis. However, in our clinical experience, we have not seen a high complication rate associated with this procedure. With care and a thorough knowledge of the anatomy and neighboring structures, this procedure is reliable, reproducible, and safe. Moreover, a posterior capsulotomy allows for a full return to sport without incidence of recurrence. In our previous patients treated through a posterior capsulotomy, no patients have reported a full return of flexion contracture. Although some patients have undergone additional surgery, any further surgery was done to treat tibiofemoral cartilage degeneration. However, the patients remained satisfied with their initial results from the posterior capsulotomy.

Lobenhoffer et al. reported extension recovery in 24 patients with flexion contracture who underwent posterior capsule release of the knee. Postoperatively, Lysholm scores ranged from 62 to 88 whereas the knee contracture angle ranged from 17 to 2 degrees. Another recent study has also reported that open posterior capsulotomy effectively treated 12 patients with lack of full extension after anterior cruciate ligament reconstruction. In their cohort, 93% restored the complete extension after an average follow-up time of 38 months, with one complaint of knee instability at 6 months following the procedure. Some authors have suggested that arthroscopic release by a posteromedial approach may be useful to release the capsule in less severe cases.14, 15 In conclusion, an open posterior capsulotomy is a worthwhile procedure capable of effectively treating minimal extension deficit of the knee.