When strengthening it is important to include all muscles that have a function at the knee joint
Eccentric muscle contraction should be used and incorporated in isotonic exercises
Plyometric exercises use eccentric contraction to facilitate a concentric contraction
Here are some examples of exercises that involve the muscles at the knee joint:
Squats
Maintain proper form throughout squat
Gradually increase weight
Thigh should end parallel to the ground
Lunges
Do not let front knee go over the toe
Straight Leg Raise
Can be done on back or on the side
Do not rotate hips while lifting leg
Lift leg approximately 6 inches off the table or floor
Terminal knee extensions (TKE's)
Standing, use rubber tubing, place around the back of the leg for resistance, slowly flex and extend the knee, rest of the body remains still in good posture
Step ups
Use a wooden box or fitness step box, can step up sideways or facing, maintain good posture and focus on using the muscles to pull you up and guide you back down
These will help with neuromuscular control and strengthening the quads
Hamstring curls (machine)
Use a open kinetic chain weight resistance machine, adjust weight, and use both legs to curl or knee flexion
This works your hamstring muscle group
Knee extensions (machine)
Use an open kinetic chain weight resistance machine, adjust weight, and use both legs to extend the knees.
This will also help strengthen the quads
Depth jumping
More of a plyometric exercise
Will incorporate strength, function, balance, and postural control for the muscles functioning at the knee joint
Isokinetic knee extension (Biodex)
This exercise uses a special machine
Time is fixed
Mostly used in the later stages of rehabilitation for ACL injuries
Proper squatting technique. Image copied from http://www.machinemuscle.com/squats-the-king-of-all-exercises/
Proper Lunge Technique. Image copied from http://stronger-slimmer.com/hamstrings-exercise.html
Straight Leg Raise. Image copied from http://physicaltherapy.about.com/od/rehabex/ht/SLR.htm
Terminal Knee Extensions. Image copied from http://jan.ucc.nau.edu/mtl8/Ther_Ex_files/LE_ex.htm
Step Ups. Image copied from http://www.athleticadvisor.com/injuries/le/quad_strengthening.htm
Hamstring Curls. Image copied from http://www.exerciseplace.org/december.html
Knee Extensions. Image copied from http://trendyupdatefitness.blogspot.com/2012/05/only-one-type-to-train-your-quadriceps.html
Depth Jumping. Image copied from http://howtojumphigherfaster.com/special-offer/