Acute Knee Injuries


The key feature of the knee examination is that each structure that may be injured must be examined. Clues to diagnosis are gleaned from the presence or absence of swelling, assessment of the state of the ligaments and menisci, and range of motion testing.

Meniscal Injuries

Acute meniscal tears occur when the shear stress generated within the knee in flexion and compression combined with femoral rotation exceeds the menisci’s ability to resist these forces.

Clinical Features

1. The most common mechanism of meniscal injury is a twisting injury with the foot anchored on the ground.

2. The degree of pain associated with an acute meniscal injury varies considerably. Some patients may describe a tearing sensation at the time of injury.

3. A small meniscal tear may cause no immediate symptoms; it may become painful and cause knee swelling over 24 hours.

4. Small tears may also occur with minimal trauma in the older athlete as a result of degenerative changes within the meniscus.

5. Patients with more severe meniscal injuries, for example, a longitudinal (‘bucket handle’) tear, present with more severe symptoms. Pain and restricted movement  occur soon after injury. Intermittent locking may occur as a result of the torn flap, the ‘bucket handle’, impinging between the articular surfaces. This may unlock spontaneously with a clicking sensation.


The signs of a meniscal tear include :-

1. joint line tenderness with the knee flexed between 45-90 degrees

2. Joint effusion with varying levels

3. Pain on squatting

4. Restricted range of movement of the knee joint due to the torn meniscal flap or swelling.

McMurrays Test

This flexion / rotation test is positive when pain is produced by the test and a clunk is heard or felt that corresponds to the torn flap being impinged in the joint. However, the clunk will not always occur and the hyper-flexion portion of the McMurrays test provokes pain in most meniscal injuries. Pain produced by flexion and external rotation is often indicative of medial meniscal damage, whereas pain on internal rotation indicates lateral meniscal pain.


MRI examination is the investigation of choice. This can aid management if the MRI shows either a complex tear or minimal damage, or more rarely, a peripheral meniscus tear. If meniscal tearing is minimal and stable without displacement, clinical progress remains the best measure of non-operative management. Peripheral meniscus tears, depending on the length of the tear, may be surgically addressed.


The management of meniscal tears varies depending on the severity of the condition. At one end of the spectrum, a small tear or degenerative meniscus should initially be treated conservatively. On the other hand, a large painful ‘bucket handle’ tear, causing a locked knee, requires immediate arthroscopic surgery.

The majority of meniscal injuries fall somewhere between these two extremes and the decision on whether to proceed immediately to arthroscopy must be made on the basis of the severity of the symptoms, as well as the demands of the athlete.


The aim of surgery is to preserve as much of the meniscus as possible. Some meniscal lesions are suitable for repair by meniscal suture, which can be performed with an arthroscope. The decision as to whether or not to attempt meniscal repair is based on several factors, including acuity of the tear, age of the patient, stability of the knee, and tear location and orientation.

The outer one-third of the meniscus rim has a blood supply, and tears in this region can heal. The tear with the best chance of a successful repair is an acute longitudinal tear in the peripheral one-third of the meniscus in a young patient. Degenerative, flap, horizontal cleavages and complex meniscal tears are poor candidates for repair. Partial tears may require removal of the damaged flap of the meniscus.

Rehabilitation after Meniscal Surgery

Rehabilitation should commence prior to surgery. In this pereiod it is important to :-

1. reduce pain and swelling with the use of electrotherapeutic modalities and gentle range of movement exercises

2. maintain strength of the quadriceps, hamstrings, hip abductor and extensor muscles.

3. protect against further damage to the joint (crutches if necessary)

The precise nature of the rehabilitation process will depend on the extent of the injury and the surgery performed. Arthroscopic partial menisectomy is usually a straightforward procedure followed by a fairly rapid return to activity (after 4 weeks of rehabilitation).

The rehabilitation process usually takes longer if there has been a more complicated tear of the meniscus, especially the lateral meniscus. The presence of associated injuries, such as articular cartilage or ligament tears will naturally slow down the rehabilitation process.

Rehabilitation principles after arthroscopic partial menisectomy are :-

1. to control pain and swelling

2. to regain pain-free active range of movement

3. graduated weight-bearing

4. progressive strengthening within the available range of movement

5. progressive balance, proprioceptive and coordination exercises

6. return to functional activities

Conservative Management of Meniscal Injuries

Conservative management of relatively minor meniscal injuries will often be successful, particularly in the athlete whose sporting activity does not involve twisting activities. The principles of management are the same as those shown above.

The criteria for return to sport following meniscal injury, treated surgically or conservatively are as follows and accordance to strict rehabilitation :

1. absence of effusion

2. full range of movement

3. normal quadriceps and hamstring function

4. normal hip external rotator function

5. good proprioception

6. functional exercises performed without difficulty

7. training performed without subsequent knee symptoms

8. stimulated match situations undertaken without subsequent knee symptoms

Medial Collateral Ligament (MCL) Tears

Injury to this ligament occurs as aresult of a valgus stress to a partially flexed knee. This can occur in a non-contact mechanism such as downhill skiing, or in contact sports, resulting from a fall or a tackle. MCL tears are classified on the basis of their severity into grade 1 (mild), grade 2 (moderate) and grade 3 (complete).

Grade 1

There is local tenderness over the MCL on the medial femoral condyle or medial tibial plateau, but usually no swelling. When a valgus stress is applied at 30 degree of flexion, there is pain but no laxity. Ligament integrity is intact.

Grade 2

Produced by a more severe valgus stress. Examination shows marked tenderness, sometimes with localised swelling. A valgus stress applied at 30 degree of knee flexion causes pain. Some laxity is present but there is a distinct end point. Ligament integrity is compromised but intact through its length.

Grade 3

Results from a severe valgus stress that causes a complete tear of the ligament fibres. The patient often complains of a feeling of instability or a ‘wobbly knee’. The amount of pain is variable and frequently not as severe as one would expect given the nature of the injury. On examination, there is tenderness over the ligament and valgus stress applied at 30 degrees of flexion reveals gross laxity without a distinct end point.


The treatment of MCL injuries involves a conservative rehabilitation programme. Patients with grade 3 injuries that have been treated conservatively have been shown to return to sport as well as those treated surgically. The rehabilitation programme varies depending on the severity. A hinged knee brace provides support and protection to the injured MCL during the rehabilitation process. A more severe injury will require a longer period of rehabilitation.

Anterior Cruciate Ligament (ACL) Tears

Tears of the ACL are relatively common among sports people. They occur most frequently in those who play sports involving pivoting (e.g. soccer, rugby, basketball, skiing). The incidence rate of ACL tears is between 2-9 tomes higher in female athletes competing in similar activities.

ACL tears may occur in isolation or in combination with associated injuries, particularly meniscal and articular cartilage injury, or injury to the MCL.

Clinical Features

The majority of ACL tears occur in a non-contact situation, when the athlete is landing from a jump, pivoting or decelerating suddenly. The typical features of the history include the following :-

1. The patient often describes an audible ‘pop’, ‘crack’, or feeling of ‘something going out and then going back’.

2. Most complete tears of the ACL are extremely painful, especially in the first few minutes after injury.

3. Athletes are usually unable to continue their activity, which is usually associated with a large effusion (hemarthrosis). Occasionally, swelling is minimal or delayed.

4. At times, tries to recommence the sporting activity and feels instability or a lack of confidence in the knee.

Examination Findings

1. Athletes have restricted movement of the knee, especially loss of extension.

2. They may have widespread tenderness

3. Lateral joint line tenderness is often present

4. Medial joint line tenderness may be present if there is an associated medial meniscal injury

5. The Lachman’s Test, anterior drawer, pivot shift (jerk test) are all positive in ACL disruption and is the most useful test for this condition


1. X-ray of the knee should be performed when an ACL tear is suspected. It may reveal an avulsion of the ligament from the tibia or a ‘Segond fracture’ at the lateral margin of the tibial plateau.

2. MRI scanning is also useful in demonstrating an ACL tear when the diagnosis is uncertain clinically.

3. A bone bruise is usually present in conjunction with an ACL injury. The most common site is over the lateral femoral condyle. The presence of a bone bruise indicates impaction trauma to the articular cartilage.

4. It may be that those patients with a bone bruise are more prone to the development of osteoarthritis.

Conservative or Surgical Management ?

Once the diagnosis is made, the decision on whether to opt for initial conservative or surgical management is dependent on a numbeer of factors :

1. the age of the patient

2. the degree of instability

3. associated abnormalities (e.g. MCL tear, meniscal tear)

4. whether or not the patient performs pivoting sports

5. the patients occupation

6. social factors

7. if the patient indicates a lack of willingness to undertake appropriate rehabilitation, surgery may not be successful.

8. Surgery should be recommmended for those athletes wishing to participate in a high-speed sport with constant changes in direction and pivoting.

Surgical Treatment

There are numerous surgical techniques used in the treatment of ACL injuries. As ACL tears are usually in-substance tears and therefore not suitable for primary repair, reconstruction of the ACL is the surgical treatment of choice.

The aim of ACL reconstruction is to replace the torn ACL with a graft that reproduces the normal kinetic functions of the ligament. In most cases, an autogenous graft , taken from around the knee joint, is used.

The most common grafts used are the bone-patellar-bone autograft involving the central third of the patellar tendon or the hamstring (semitendinosus, gracilis) graft.

Other graft options include allografts (the transplantation of cadaver tissue such as ligaments or tendons). It has been suggested that allografts may be associated with an earlier return to sport.

Before surgery is carried out, the knee should have little or no swelling, have near full range of motion, and the patient should have a normal gait. This period until surgery is termed ‘prehabilitation’.

Rehabilitation after ACL Reconstruction


Rehabilitation must commence from the time of injury, not from the time of surgery, which may be days, weeks or months later. Pre-operative management aims to reduce aims to reduce pain, swelling and inflammation, thus reducing the amount of intra-articular fibrosis and resultant loss of range of motion, strength and function. Immediately after injury, treatment should commence, including interferential stimulation, ultrasound, and strengthening exercises for the quadriceps, hamstrings, gluteals and calf muscles. Pain-free range of motion exercises should also be performed.


Immediately following surgery, weight-bearing status is largely determined by concomitant injuries (e.g. meniscal repair). Isolated ACL reconstructions are typically treated as weight-bearing as tolerated, using a brace and/or crutches until adequate quadriceps muscle strength is restored.

The rehabilitation programme for patellar tendon and hamstring tendon graft ACL reconstructions are slightly different due to the need to prevent the particular complications associated with each type of reconstruction. The main problem with the patellar tendon graft is anterior knee pain. Therefore, attention must be paid to this area during the rehabilitation programme with the use of soft tissue therapy to the patellar tendon, accompanied by a strengthening programme for the tendon, and patellar taping to prevent patello-femoral and fat pad problems. The hamstring graft should be treated as though the patient has had a hamstring tear, with an appropriate rehabilitation programme to restore full range of motion and strength.

Rehabilitation Programme

As a general guideline, the following milestones are targeted before return to full sporting activity :

Phase 1 (0-2 weeks)


Full weight-bearing, eliminate swelling, regain, quadriceps / hamstring static strength


Cryotherapy, Electrotherapy, Gait re-education

Exercise Programme

Flexion / extension range of motion exercises; (regain full extension); Inner range quadriceps strengthening, bilateral calf raises, hamstring pulleys, abduction / gluteal exercises

Phase 2 (2-12 weeks)


No swelling, full knee hyper-extension, full squat, improving balance, unrestricted walking


Cryotherapy, Electrotherapy, Gait re-education

Exercise Programme

Range of motion exercises; mini squats; lunges; leg press (double then single), step ups; bridges, single leg calf raises, balance / proprioception drills, walking, exercise bike

Phase 3 (3-6 months)


Full range of movement, full strength and power, return to jogging, running and agility, return to sports-specific drills


Exercise supervision

Exercise Programme

As above with increased difficulty, repetitions and weight; jump and land drills; hopping; agility drills, running / change of direction drills, kicking

Phase 4 (6-12 months)


Return to sport


As above

Exercise Programme

High-level sports-specific strengthening; progressive unrestricted training, return to full training.

Most surgeons support that ACL graft maturation takes up to 6 months, and advocate a 6 month return to sport as an initial guideline. Beyond this, functional testing, as described, is used to help assess readiness to return to sport.

Various functional tests include agility tests, the standing vertical jump and the ‘Heiden Hop’. The patient performs the ‘Heiden Hop’ by jumping as far as possible using the uninjured leg, landing on the injured leg. Athletes with good function are able to land solid with a single hop and ‘stick it’. Those with functional disability step further or take another small hop.

Another way of testing function is by incorporating isokinetic testing to evaluate muscle strength. Quadriceps strength should be at least 90% of the uninjured leg and hamstring strength at least 100%.

Posterior Cruciate Ligament Tear (PCL)

Tears of the PCL do not appear to be as common as the ACL. PCL injuries are often associated with meniscal and chondral injury.

Clinical Features

The mechanism of PCL injury is usually a direct blow to the anterior tibia with the knee in a flexed position. Knee hyperextension may also result in an injury to the PCL and posterior capsule.

The patient usually complains of poorly defined pain, mainly posterior, sometimes involving the calf. The posterior drawer test is the most sensitive test for PCL deficiency.

X-ray should be performed to exclude a bony avulsion from the tibial insertion of the PCL. It is considered that more than 7-8mm of posterior translation is indicative of a PCL tear. MRI scanning also has a high predictive accuracy in the diagnosis of acute PCL injury.


PCL rupture can generally be managed conservatively with a comprehensive rehabilitation programme. Surgical reconstruction is indicated when the PCL injury occurs in combination with other posterolateral structures or where significant rotatory instability is present.

Rehabilitation Programme

Phase 1 (0-2 weeks)


Full weight-bearing; 0-100 degree knee flexion; improve hamstring / quadriceps strength.


Cryotherapy, electrotherapy, gait re-education

Exercise Programme

Knee flexion / extension ROM exercises; Quadriceps / hamstring strengthening; bilateral calf raises

Phase 2 (2-4 weeks)


No swelling, full ROM, increase hamstring / quadriceps strength


Cryotherapy, Electrotherapy

Exercise Programme

ROM drills; Mini squats and lunges; Leg press (double, then single); Step ups; Bridges (double, then single); Hip abduction and extension with rubber tubing; Single leg calf raises; Single leg balance and proprioceptive drills; Walking, Exercise Bike

Phase 3 (4-6 weeks)


Full range of motion; full strength and power; return to jogging, running and agility; return to restricted sport-specific drills


Exercise modification / supervision

Exercise Programme

As before, but include plyometric-type drills; running drills, change of direction drills, jumping, hopping, kicking.

Phase 4 (6-10 weeks)


Return to sport


As above

Exercise Programme

High-level sport-specific strengthening as required; competitive match play.

Articular Cartilage Damage

Articular cartilage damage may occur as an isolated condition, or in association with other injuries to the knee (ie. MCL, ACL, PCL) and can have both short and long-term effects. In the short term, it causes recurrent pain and swelling. In the longer term, it accelerates the development of osteoarthritis. Various methods have been used to encourage healing of articular cartilage defects.

These include microfracture, mosaicplasty, autologous chondrocyte implantation. Although short-term reduction of symptoms have been shown with these treatments, long-term reduction of arthritic disability has not been established. As yet, no method of treatment has been able to reproduce true hyaline cartilage.

Following articular cartilage injury, the athlete may have to modify his or her training to reduce the amount of weight-bearing activity and substitute activities such as swimming and cycling. Continuous passive motion machines are also highly beneficial, particularly in the immediate post-operative period. Proprioceptive and strengthening exercises are also essential in reducing stress on the repaired articular cartilage.

Acute Patellar Trauma

Patella Dislocation

Patella dislocation occurs when the patella moves out of its groove laterally. Patients usually complain of the knee giving way upon twisting or jumping, followed by the development of severe pain. Often the patient will describe a feeling of something ‘popping out’. Swelling develops almost immediately. The dislocation usually resolves spontaneously with knee extension, however in some cases this may require some assistance.


Relatively atraumatic dislocations are treated conservatively and rehabilitation. Recurrent dislocation is treated with surgical stabilisation.

The most important aim of rehabilitation after dislocation is to reduce the chances of a recurrence of the injury. As a result, the rehabilitation programme is lengthy and emphasises core stability, quadriceps strengthening and stretching of the lateral structures.

Rehabilitation Programme Following Patella Dislocation

Phase 1 (0-2 weeks)


Control swelling; maintain knee extension and isometric quadriceps strength


Extension splint, cryotherapy, taping, electrotherapy

Exercise Programme

Quadriceps drills, bilateral calf raises, progress to full weight-bearing

Phase 2 (2-6 weeks)


No swelling; full extension; flexion to 100 degrees, improved quadriceps strength, full hamstring strength


Cryotherapy, electrotherapy, manual therapy, gait-re-education

Exercise Programme

Range of motion drills; mini squats / lunges; bridging, hip abduction and extension strengthening, single leg calf raises, balance and proprioception drills, walking, exercise bike

Phase 3 (6-8 weeks)


Full range of motion; full strength and power, return to jogging, running and agility, return to restricted sport-specific drills


Exercise supervision / modification

Exercise Programme

As above with increasing difficulty, repetitions and weight; single leg squats, single leg press, jump and land drills, agility, running drills, change of direction drills, kicking

Phase 4 (8-12 weeks)


Return to sport

Exercise Programme

High-level sport-specific strengthening, return to competitive training and play