1. Knee injuries

2. Knee joint (anatomical view)

3. Dislocation of the patella
Because the knee is normally angled in slight valgus, there is a natural tendency for the patella to pull towards the lateral side when the quadriceps muscle contractd laterally by violence. Mechanisim of injury : sudden, severe contraction of the quadriceps muscle while the knee is stretched in valgus and external rotation. Patients with joint hypermobility, valgus knee, muscle and joint abnormalities prone to this injury.

4. Dislocation of the patella

5. Clinically :
The knee collapses and patient fall on ground. Patella can be felt on outer side of knee or the patella springs back into position spontaneously. The X- ray shows dislocation of patella laterally and associated fractures if present.
Treatment :
In most cases the patella can be pushed back into place without much difficulty and anaesthesia is not always necessary. A plaster slab is applied with the knee in extension for 3 weeks and quadriceps exercises. However, if there is much bruising, swelling and tenderness medially, the patellofemoral ligaments and retinacular tissues are probably torn and immediate operative repair will reduce the likelihood of later recurrent dislocation. Complication is recurrences.

6. Fractures of patella
it can be caused either by: A- direct force :lead to undisplaced crack or comminuted fracture and here the extensor expansion usually remain intact (the patient can elevate striaght leg). B- indirect force : lead to transverse fracture with gap between the fragments Caused by resisted extension ( sudden contraction of the quadrecepse muscle against resistant ). Associated with tears of collateral extensor expansions and failure of extensor mechanism (patient cannot elevate leg straight).

8. Treatment : For the fractures caused by direct force : In undisplaced or minimally displaced fractures The treatment is by p.o.p cylinder holding the knee straight should be applied for 3–4 weeks , during this time quadriceps exercises are to be practised,haemoarthrosis should be aspirated. Severely comminuted and displaced fracture treated by internal fixation or delayed patellectomy. For the fracture caused by indirect force: . Operation is essential. Through a longitudinal incision the fracture is exposed and the patella repaired by the tension-band principle . The tears in the extensor expansions are then repaired.

9. Internal fixation/pop cylinder

10. Knee dislocation
The knee can be dislocated only by considerable violence, as in a road accident. The cruciate ligaments and one or both lateral ligaments are torn. There is sever swelling , bruises and knee deformity. The circulation and sensation in foot must be examined to exclude popliteal vessels and nerve injuries..

11. Knee dislocation

12. Treatment : URGENT reduction by closed or open reduction followed by splinting the knee in 15 degrees flexion for 12 weeks and physiotherapy. Repeated check of circulation is essential, If the joint is unstable anterior external fixator applied. If there is open wound or vascular injury the opportunity is taken to repair the ligaments and capsule. When swelling subsides, a cast is applied for 12 weeks. Quadriceps exercises encouraged from the start, and knee range of motion exercises after plaster removal. Complications: Early complications are arterial injures and nerve injuries. Late complication are chronic instability.

13. Meniscus injury
Meniscus injury are common in young adult especially football players, result from twisting of semi-flexed or flexed knee. The medial meniscus torn more than lateral meniscus. The tear might affect the anterior or posterior horn of meniscus as pedunculated tag , or as bucket handle, sometimes horizontal tears or degeneration might occur. Patients give history of trauma, pain, inability to extend knee and delayed swelling of knee. Locking (in ability to fully extend the knee) and unlocking are common feature of meniscus injury . Diagnosis of meniscus injury depend on classical history and clinical finding. MRI is reliable method of diagnosis, arthroscopy can be used to confirm the diagnosis. The treatment of choice is to remove the teared segment of meniscus arthroscopically. Arthroscopic repair used for peripheral lesions.

15. Injuries of the tibia
Tibial plateau fractures: Direct blow or fall from height may cause fracture of one tibial condyle or both. Fracture lateral condyle is the commonest named as bumper fracture caused by a force that abducts the tibia upon femur while the foot is fixed on ground. Patient usually is an adult, the knee joint is swollen, bruises, there is diffuse tenderness and doughy feel of haemarthrosis.ligaments injuries must be excluded. Imaging : X-ray: anteroposterior, lateral & oblique views. ct -Scan may used to detect amount of depression and comminuation.

16. Tibial plateau fracture

17. Treatment: Undisplaced fractures treated conservatively: Haemarthrosis aspiration and compression bandaging,above knee cast for one months followed by functional brace and physiotherapy. For displaced fractures treatment is by open reduction and internal fixation with plate and screws as it is an intra articular fracture.

18. fixation of tibial plateau fracture

19. Complications : 1- Vascular injuries and nerve injuries
Complications : 1- Vascular injuries and nerve injuries. 2- Compartment syndrome (specially with severe condylar fractures). 3- Joint stiffness (prevented by early range of motion exercises). 4- Deformity (Varus or Valgus), Valgus deformity are common complication. 5- Secondary osteoarthritis (due to residual depression, knee deformity or ligament instability) .