Knee sprain

Knee sprains mostly affect the medial and tibial collateral ligaments. However, these injuries are often not isolated and may involve other structures at the same time, such as the menisci, the cruciate ligaments, the capsule or even the oblique popliteal ligament. This is why it is important to have a full physical examination by a specialist staff, even if the trauma is thought to be simply a « benign » sprain. 

MRI is the best examination to assess the trophic and structural state of the knee, but it is often difficult to get an appointment quickly, unless you are a high-level sportsman. 

Anatomically, which ligaments are we talking about ?

The tibial collateral ligament (TCL) originates from the medial epicondyle of the knee and extends distally to insert itself onto the tibia deep within the anterior border of the sartorius (1).

The lateral collateral ligament (LCL) is the primary varus stabiliser of the knee. In addition, the LCL acts as a secondary brake on external rotation and posterior displacement of the tibia (2), combining its capabilities with the cruciate ligaments for good knee stability. 

3 main grades exist for knee sprains : 

• Grade 1 = « Benign » sprain : simple stretching of the ligament fibres, subcutaneous fluid surrounding one or both ligament insertions, no immobilisation required but monitoring is to be applied. Physiotherapy should always be considered in this type of injury because although the name suggests Grade 1 as benign, a sprain should never be considered as harmless. 
• Grade 2 = Moderate sprain : morphological rupture of the ligament involving partial tearing of the ligament fibres, internal hyperintensity may be seen in the ligament and/or in the bursal fluid around the ligament, with loss of demarcation of the adjacent subcutaneous fat. Immobilisation with a splint lasts for about 3 weeks but the time frame can be adapted according to the injury. Then the physiotherapeutic treatment takes all its importance since it is a question of offering the injured knee an optimal healing without risking to disturb the tissue regeneration by applying too fast intensities and loads, again this notion of progressiveness. 
• Grade 3 = Severe sprain : total tear of the ligament in its middle substance or its insertions, often associated with increased oedema. Immobilisation is required with a splint for about 6 weeks, support is authorised if there is no pain and with the help of crutches but above all the advice of the doctor, surgeon or physiotherapist. Re-education is also essential to hope for a return to the field with the same sensations as before. Despite this, surgery is rare, except for sporting or professional requirements (3)(4)(5). 
  

However, when injuries to other ligamentous structures are present, early surgical intervention may be beneficial (6). It has also been shown that a tear in the LCL does not heal as well as a tear in the medial collateral ligament, therefore the study by Grawe B et al advocates a lower threshold for surgical intervention for a tear in the TCL (2).

What tests should be applied ?

There is a main test carried out internally and externally :

Knee bent at 30°, the patient is on the table in a semi-seated or lying position. The physio will push the knee inwards by blocking the tibia (valgus) or push the knee outwards by also blocking the tibia (varus). When pushing inwards, the medial collateral ligament is strained while when pushing outwards the lateral is strained. The test is positive if there is pain, discomfort and if it reproduces the basic symptoms. Localized palpation is also important to detect any tenderness or pain in the patient. 

As with all tests, it is important to always compare the two legs so that the player can have a notion of how the sensations compare. 

What rehabilitation for a knee sprain ?

The physiotherapist’s work will initially consist of treating the inflammation and oedema using massage techniques, cryotherapy or suction cups. The second objective is to recover the mobility and amplitude of a healthy knee as quickly as possible. For this aspect of the treatment, gentle passive mobilisations will be indicated in order to evolve to active movements and contract-release in particular. Hamstring fatigue is also a point of interest when a patient presents with flessum (a knee that cannot be fully extended) after prolonged immobilisation or surgery. 

Once the amplitudes have been recovered and the pain has disappeared, a reinforcement of all the structures allowing stabilisation and active locking of the knee can then take place. The muscles mainly concerned by this muscular development are obviously the quadriceps but also the gluteal muscles which allow a good hip-knee-ankle alignment. If you want to focus on an TCL sprain, then it is worth trying to target the semimembranosus and the popliteus. The LCL sprain should be worked on by strengthening the hamstrings and the Fascia Lata tensor (TFL). In parallel to this muscular programme, it is essential to set up a functional and proprioceptive reinforcement to include ball exercises and a return to the field in line with the progressions. 

It should be noted, however, that for a knee sprain, depending on the severity of the injury, it takes several weeks for optimal healing and rehabilitation. 

How can knee sprains be prevented ?

The prevention of collateral ligament sprains is similar to that for the prevention of cruciate ligament injuries. Indeed, it must include work on various supports, a global muscular reinforcement of the whole lower limb by working in a symmetrical or asymmetrical way. Real work on the landing phases of jumps should also be put in place, as well as the importance of working on the good mobility of the ankle in dorsal flexion. The importance of this amplitude is also developed in the section on the prevention of cruciate ligament injuries.  

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