Exercise and rehabilitation programs for osteoarthritic (OA) knees have often been limited due to fear of exacerbating inflammation and joint cartilage destruction. Some programs have even been restricted to gentle range of motion and stretching exercises only.  This article outlines strengthening techniques that have been used practically in clinic and gym settings that have achieved great results.

Rest and a reduction in movement are often recommended as treatment for osteoarthritic knees.  However, immobilising a knee joint has some serious consequences for recovery.  Loss of muscle strength during immobilisation occurs at 1–2% a day so conditioning is vital during rehabilitation. A literature search confirms that both isometric and isotonic resistance training can benefit osteoarthritic patients/clients. There is a fine balance between the beneficial effects of rest and exercise when training clients with osteoarthritis, and the best balance needs to be determined individually for each patient.

In my opinion, a rehabilitation programme should include isometric, isotonic free weight exercises that involve multi-joint functional movement patterns – functional meaning that people are trained to maintain their center of gravity over their base of support in exercises chosen to help strengthen movement patterns required in ADLs, a job or sports environment.

It is important to remember that the degenerative knee will only tolerate a limited range of motion under load in early stage rehabilitation.  However, as muscle co-contraction around the joint improves, shear forces and inflammation diminish and so loads and exercise tolerances can be progressed. Goal exercises include the squat and the static lunge as these are regularly performed in daily activities. Attempting to move our clients towards these movement patterns results in effectively activating and loading all agonists, antagonists, neutralizers and stabilizers in a closed kinetic chain environment.  See figure 1.

Figure 1. The squat is a functional multi-joint movement pattern that require the client to learn to balance their center of gravity over the base of support.

Isolated strengthening exercises do not carry over into function movement patterns.   Studies have consistently found that after isotonic or isokinetic knee extensions and flexions, clients may still be unable to handle their body weight in these functional exercises.  It was also found that exercise-induced muscle pain was least with isometrics, making this an effective contraction mode to introduce resistance training. Isometrics may be used for strength gain with minimal joint motion. Research indicates a 30^o carry-over (+/^_15^o ) for strength gained at any specific joint angle. This means that strength gained isometrically at 15^o, 45^o and 75^o will improve function through the range of 0-90^o.

This principle can be used to prepare a client for squat training.  Start the client training the hip extensors, hamstrings and quadriceps and core musculature using a swiss ball. For example you can start with exercises out of standing utlising the principles of overflow to the knee joint while moving other body parts. See example of a single arm bench press in figure 2.

Figure 2. Single arm dumbbell Swiss ball chest press.  This exercise can be used as an overflow exercise to indirectly train the knee joint

There are many examples of exercises using a Swiss ball in prone and supine that will stimulate strength in the lower extremity without directly overloading the degenerative knee.

Other exercise examples in the seated position can have similar loading demands on the knee through overflow training. See figure 3 – seated posture trainer.

Figure 3. The seated posture trainer.

Once the client is able to stand painfree then loading may commence in a standing position. Isometrics may be started in both the squat and static lunge position. To perform the squat and lunge movements, allow the client to assist themselves into pain free positions of a squat or static lunge by holding a rope attached to a tension gauge, or simply hold a bar racked high in a squat rack as a means of unweighting themselves as they get into positions. Dowel sticks can be used if neither of these options are available (Figure 4).  From here the client can perform isometric squats or lunges in pain free positions and train in multiple joint positions.

Figure 4. Unweighting a lunge pattern using dowel rods.

When introducing these exercises note that muscular time-under-tension (TUT) is a critical factor for gaining strength.  Slow tempo training is very good for developing muscle mass in the initial phase. Tempo refers to the times in seconds taken to perform the eccentric and concentric movements of one repetition. Total time taken to do one set should never last longer than sixty seconds when strength development is the goal (zone of A.T.P./lactic acid energy systems), High repetitions may risk further inflaming a joint and so if the joint is moved slowly or held statically then time under tension can be manipulated so that the joint has the correct time under load but with less repetitions. This means the joint increases muscle mass without using high reps or high loads to do so.

The intensity or amount of load is also a critical programming variable.  Look to maintain loads to around 40-70% of the maximal voluntary contraction (MVC) in order to recruit type 1 and type 2A fibres to assist in stabilizing the joint and until inflammation is controlled. In painful situations the load or intensity may drop to below 40% MVC to allow the exercise to be performed.

Occasionally isotonic resistance exercise can be used early in the process, but programs must follow a strict protocol for reps, sets, tempo, loading and rest times. By the nature of the dysfunction, any exercise approach taken must be very concise, allowing only the essential number of repetitions to be performed or exacerbation will limit progress.

As well as attending to the painful knee joint, is vital to assess the dynamic core control of the trunk, pelvis and lower limb.  For example,iIf there is a pronating foot then this will create excessive torsion in the knee leading to internal femoral rotation and anterior pelvic tilt associated with weak lower abdominals and poor overall core control.  If the foot is stabilized with orthotics but there is still lack of control of rotation of the femur and lack of control of the lower extremity and pelvis, then this will create more torsion in the knee on a fixed tibia - this can very quickly increase knee degeneration and inflammation. Therefore ensure that flexibility improvements and strength gains are not limited to around the knee joint but to both proximal and distal joints and the trunk. More details from the article will be covered in the Practical Programming for Exercise Rehabilitation workshop.