KNEEissues and Clinical Casebook

It is well documented that women suffer 4-6 times the number of knee injuries during sport than do men. A few years ago, our team at the Cincinatti Sportsmedicine Research and Education Foundation attempted to determine whether this statistic could be reversed by specific training of women prior to undertaking sports activities [see original publication].

The National Collegiate Athletes Association (NCAA) estimated an incidence of 1 in 10 knee injuries amongst the 100,000 American collegiate women participating in sports each year.

They drew attention to the massive cost - pointing out that cruciate ligaments alone in this group cost US$37 million a year! They estimate the total annual cost of serious knee injuries in USA women athletes (high school plus college) to be in the order of US$100 million a year.

In our study we set out to determine whether specific pre-sports training might reduce this crippling expense. 

Explanations in the medical literature for the comparatively high incidence of knee injuries in women included:

• different levels of training and coaching
• physiologic differences such as increased joint laxity, with oestrogen being fingered as the main suspect
• anatomic differences in pelvic structure with greater angulaton of the femur (thighbone) in women
• narrow intercondylar notch - the gap between the rounded ends of the femur - in which the anterior cruciate ligament (ACL) is contained
• the smaller ACL of women
  

In a previous study in which I had been involved our group had found that four out of five ACL injuries in athletes occurred from a non-contact mechanism, the majority occuring while landing from a jump. We decided in this new study to take our investigations further, and give a group of 366 women a comprehensive program of training and coaching throughout a season, including particular emphasis on landing from jumping.

This study group we would then compare with two ‘control’ groups -

• a group of 434 men not given any pre-sports instruction or training
• a second group of 463 women, again not given any pre-sports instruction or training

We had taken all three groups from well known jumping sports - volleyball, soccer or basketball.  All were high school aged athletes.

Coaches of the test group of women were given an instructional video and training manual to cover a six week program incorporating flexibility, plyometrics and weight training. Details of the regime are in the appendix of our original publication. An athletic trainer and physiotherapist were also assigned to the groups to demontrate plyometrics and stretches, and to improve form. The other two groups did not participate in the training programme.

Over the period of study we managed to monitor 94% of the athletes through the entire season and all knee injuries were carefully documented.  Any suspected ACL ruptures were confirmed by arthroscopy. Standard statistical methods were used to analyse our results. There were some design faults in our study, but we nonetheless feel that the results are significant.

What did we find?
There were no serious knee injuries in the volleyball players in any of the groups. Taking the results for soccer and basketball, though, we found the untrained female athletes had 5.8 times the number of knee injuries than the men.  Lack of training particularly predisposed the women to ACL injury.

Training significantly reduced the number of injuries in women, but even then this group had 2.4 times the number of injuries as the men, suggesting that factors other than training are also very relevant. 

Hams to quads ratio
Hamstrings muscles resist the forces that strain the ACL, while the quadriceps muscle has the opposite effect.  In untrained female athletes the quads are generally relatively stronger than the hamstrings, and the ACL is put at risk.  Hamstrings-to-quads ratio should be about 65% in the trained knee.  Ratios below 60% predispose the ACL to injury. Ratios below 50% should be considered abnormal.

We believe that the major benefit of a jump training program which includes progressive resistance weight training for the lower extremity, other than a general improvement in technique and strength, is gained from improvement of the hamstrings-to-quadriceps ratio.

Improvement is also gained from decreasing what is called ‘abduction and adduction moment’, ie stabilizing the knee from stressing into a bow- or knock-knee position on landing.

In conclusion
We recommend that serious attention be given to instituting similar training programmes in women’s teams where jumping and landing put the ACL at risk, in order to reduce cost both in terms of medical care and personal suffering. Specifically hamstrings-to-quads ratio should be optimised to protect the ACL.

Cincinatti Sportsmedicine Publication list

Meniscal transplantation provides hope for the many thousands of patients in whom total meniscectomy has altered the shock-absorbing qualities of the knee, with consequent stresses in the vertical alignment of the lower limb and damage to the joint surfaces. But meniscal transplantation is still in its early days. The pioneers of this procedure are carefully reviewing their patients after the first three or four years - and presenting their findings, concerns and recommendations.

This paper summarises a peer-reviewed publication in the Journal of Bone & Joint Surgery of July 2004 (Meniscal Transplantation in Symptomatic Patients Less Than Fifty Years Old Noyes et al. J Bone Joint Surg Am.2004; 86: 1392-1404) presenting the results of thirty eight meniscal transplant patients nearly four years after surgery.

The study was prospective - i.e. evaluation was begun before surgery was undertaken, allowing comparison of the results of surgery with the pre-operative findings.

An evolving science
Meniscal surgery has evolved through a number of phases, and it is now well recognised that meniscal tears amenable to suture (stitching) should be repaired rather than removed. However, if considerable damage has occurred it may still in some cases be necessary to remove the greater part of this important shock-absorbing structure, leaving the knee vulnerable to stress.

That transplant should restore the load-bearing function is generally accepted, but amongst clinicians there is a considerable lack of agreement, not only about the actual efficacy of the procedure, but also about the methods of ‘harvesting’ and sterilising the donor meniscus.

Our patient series
The series included thirty-eight patients (20 male, 18 female, average age 30 years) but forty meniscal transplants, as two patients had both medial and lateral (inner and outer) menisci transplanted.

All patients consented to the surgery and to participate in ongoing evaluation.  Official permission was obtained from the appropriate professional body for the special MRI studies.

All but one patient returned (average 40 months) for clinical evaluation, and the one who could not return posted all the questionnaires and was subsequently interviewed.

Indications for surgery
Prior to undertaking this study we had drawn up a clear list of indications for transplant surgery:

• prior meniscectomy
• age 50 or less
• pain in the tibio-femoral compartment (between tibia and femur bone)
• no radiographic evidence of advanced joint damage
• 2mm or more joint space on the affected side when X-rayed weight-bearing

Factors that we considered contraindications to meniscal transplant included -

• advanced joint surface damage
• significant axial mal-alignment (bow legs or knock knees) consequent on the loss of the meniscus
• knee joint instability where the patient had refused to have ligament reconstruction at the same time as the transplant
• very stiff or wasted knee or prior joint infection.

Patients in the series agreed to ligament reconstruction or repair where appropriate. They also agreed to joint surface repair (osteochondral autograft - where little plugs of healthy joint cartilage from less important areas are swapped with damaged bits on the weight-bearing surface).

Pre-operative Workup
The patient’s symptoms and signs were carefully documented before surgery was undertaken. 

All patients underwent MRI imaging. Standing X-rays were taken with the knees bent to optimise visualisation of the joint space while load bearing. Any cruciate laxity was objectively measured and documented.

A sophisticated rating system was developed to allow us to assess the success or failure of the transplant surgery based on symptoms, clinical examination, MRI, X-rays, and follow-up arthroscopy.

The Surgical Procedure
The approach to the meniscus differed depending on whether the transplant was being done on the lateral or the medial side. Lateral meniscal transplant was performed arthroscopically, but we opened the joint for the medial side as the technique is more complex.

Both medial and lateral grafts depend on the donor meniscus being prepared with bone plugs, which are embedded into holes prepared in the recipient bone.  The rim of the meniscus is sutured to the capsule.

Full details of the procedure can be obtained from our original publication.

Rehabilitation
Emphasis was given to minimising weight-bearing to allow the graft to heal without displacement, and toe-touch only was permitted for the first two weeks.  A long leg brace was prescribed for eight weeks, with quads exercises and ROM (range-of-motion) exercises of 0-90 degrees from the first day.

ROM was increased to 135 degrees by four weeks. Weight-bearing was increased to 50% of body weight by the end of the first month.

Patients who had had a cruciate reconstruction underwent a more restricted protocol, and where osteochondral autograft had been done the patient was given an unloader brace to take some of the pressure off that side.

Balance, proprioception and closed chain exercises were started once the patient was fully weight bearing (see KNEEguru dictionary for explanation).

So what were the results after 40 months?
This paper is the first report, as far as we know, where the outcome of meniscal transplant has been evaluated in patients with concomitant ligament or joint surface damage.

Four of the transplants in three patients failed in the early days and had to be removed. Only 43% of the menisci looked completely normal at the end of this period. Nonetheless 89% of patients rated the knee as improved overall and 76% returned to low-impact sport without problem. None returned to high impact sport, and we want to emphasise that meniscal transplantation does not allow a patient to return to vigorous sporting activity.

In our opinion the outcome of meniscal transplant is best if done before there is much damage to the joint surface (’arthrosis’), and we want to point out to younger patients to avoid high impact loading activities after meniscectomy to protect the joint surfaces for the future.

We do not advocate prophylactic (’preventative’) meniscal transplant, but in those younger individuals who might later benefit from the procedure we advocate that their clinician keep a careful eye over time on the state of the joint surfaces and underlying bone using relevant imaging techniques (45 degree postero-anterior weight-bearing X-rays, spiral computerised axial tomography (CAT scan) and magnetic resonance imaging (MRI scan) with use of proton-density, fast-spin-echo techniques).

If deterioration becomes evident in an unsymptomatic patient under 50, then we do advocate meniscal transplant, with the aim of restoring load sharing, shock absorption and joint cartilage protection. But it is important that we point out that long-term results are simply not available at this time as the procedure is simply too new.

What our study has shown - and this is an important finding - is that osteochondral autograft, at least in his series, allowed pre-existing joint surface damage to be proactively managed without prejudicing the transplant, and the same with cruciate ligament reconstruction .

Cincinatti Sportsmedicine Publication list

In 2003 our team at the Cincinatti Sportsmedicine Research and Education Foundation undertook research to study the outcome of meniscal repair in young active patients in whom removal of meniscal tissue would likely result in a major loss of function and future joint breakdown [see original publication].

Particularly we wanted to evaluate the results of removing meniscal tissue from the central region of the meniscus where blood supply is virtually absent despite the meniscus still functioning to protect the joint.

About 20 years ago torn menisci were frequently removed in their entirety, but it is now well recognised that menisci have an important role to play in -

• load sharing
• joint surface (cartilage) protection
• joint stabilization

X-rays and other imaging techniques have been used to demonstrate the insidious progression of joint surface destruction after meniscectomy.

From the perspective of healing, the meniscus can be divided into three areas.  The outer one-third has good blood supply and is called the ‘vascular’ or ‘red’ zone.  Blood supply diminishes as one progresses towards the flattened inner aspect - and this inner two thirds is called the ‘avascular’ or ‘white’ zone.

Knee surgeons refer to the junctions between these zones, where tears frequently occur, as -

• red-on-red
• red-on-white
• white-on-white

according to the vascularity of the edges of the tear.

Research has shown that tears in the outer red zone heal well but tears in the inner part of the white zone do not usually heal. But there is limited research data about tears of the outer part of the white zone, ie the area >4mm from the meniscal pheriphery.

Our study
We determined to evaluate the results of meniscal repair in this central zone in a group of patients under 20 years of age - assessing all patients both before and after surgery.

We also particularly wanted to evaluate the results where meniscal repair was combined with ACL reconstruction. This particular age group is important as meniscectomy in people so young condemns them to almost certain later knee problems.

Sixty-one consecutive patients under 20 were included in the study. The mean age was 16 (range 9-19).  88% had reached skeletal maturity.  In total we operated on 74 menisci (more than one in some patients), but three patients were lost to follow-up, so the results we present are of 71 menisci.

Of the 71, in 14 the ACL was intact.  Of the remainder, in 43 the ACL was repaired at the same time.  In the remaining 14, the ACL was repaired later for various reasons.

We allowed immediate knee motion and encouraged early muscle strengthening.  Full weight-bearing was only allowed after six weeks.  No squatting, running, jumping or twisting was allowed for six months.

Limitations of the study
Because this study was carried out over a 14 year period, and surgical knowledge advanced over this time, the earlier ACL procedures were done with allograft (cadaver tissue) while the later ones were done with autograft (own tissue). However, the procedure was the same (’bone-patellar tendon-bone’) and the operations were done by the same surgeon.

A problem we found was the difficulty of objectively assessing the long term integrity of the meniscus without incurring additional expense for the patients for MRI and/or follow-up arthroscopy. So we had to go largely on clinical findings, and we only proceeded to MRI and/or follow-up arthroscopy where it was clinically warranted.

What did we find?
Seventy-five percent (53 menisci) had no symptoms at follow-up. Of the 18 menisci (25%) in which the meniscal repair failed, 14 had symptoms suggestive of failure (usually pain), but 4 had no pain.  That is, the sensitivity of pain in predicting failure was low.

However, where there was pain failure was virtually always present, ie the specificity of pain as a predictor of failure was high.

ACL reconstruction at the same time did not prejudice the meniscal repair.  In fact these patients did rather better, probably because they were specifically instructed not to put the knee at further risk.

Importance of Surgical Technique
Meniscal tears heal primarily by migration of cells from the edge of the meniscal rim.  We stress to our colleagues the importance of meticulous technique in bringing the two surfaces of the torn meniscus into close opposition. We abrade the wound edges and use multiple non-absorbable sutures (stitches) every 4-5 mm.  Vertical sutures are stronger.  We fill the gap with fibrin clot if there is any loss of tissue at the repair site, and sometimes use a ‘micropick’ in the notch near the ACL to induce some local bleeding. We do not use fixation devices (eg arrows) to hold the edges together as we find it hard to get a meticulous closure.

Recommendations
With 75% having no symptoms at follow-up, we feel that it is very worthwhile to attempt repair in these young patients.

Cincinatti Sportsmedicine Publication list